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SPIRV-Tools/source/opt/graphics_robust_access_pass.cpp
David Neto af7410597e graphics robust access: use signed clamp (#3073) 
Access chain indices are always interpreted as signed integers.
So use signed clamp instead of unsigned clamp.  We must also
clamp to the max signed int for the index type.

Fixes #3072
2019-12-03 11:18:56 -05:00

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// Copyright (c) 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// This pass injects code in a graphics shader to implement guarantees
// satisfying Vulkan's robustBufferAcces rules. Robust access rules permit
// an out-of-bounds access to be redirected to an access of the same type
// (load, store, etc.) but within the same root object.
//
// We assume baseline functionality in Vulkan, i.e. the module uses
// logical addressing mode, without VK_KHR_variable_pointers.
//
// - Logical addressing mode implies:
// - Each root pointer (a pointer that exists other than by the
// execution of a shader instruction) is the result of an OpVariable.
//
// - Instructions that result in pointers are:
// OpVariable
// OpAccessChain
// OpInBoundsAccessChain
// OpFunctionParameter
// OpImageTexelPointer
// OpCopyObject
//
// - Instructions that use a pointer are:
// OpLoad
// OpStore
// OpAccessChain
// OpInBoundsAccessChain
// OpFunctionCall
// OpImageTexelPointer
// OpCopyMemory
// OpCopyObject
// all OpAtomic* instructions
//
// We classify pointer-users into:
// - Accesses:
// - OpLoad
// - OpStore
// - OpAtomic*
// - OpCopyMemory
//
// - Address calculations:
// - OpAccessChain
// - OpInBoundsAccessChain
//
// - Pass-through:
// - OpFunctionCall
// - OpFunctionParameter
// - OpCopyObject
//
// The strategy is:
//
// - Handle only logical addressing mode. In particular, don't handle a module
// if it uses one of the variable-pointers capabilities.
//
// - Don't handle modules using capability RuntimeDescriptorArrayEXT. So the
// only runtime arrays are those that are the last member in a
// Block-decorated struct. This allows us to feasibly/easily compute the
// length of the runtime array. See below.
//
// - The memory locations accessed by OpLoad, OpStore, OpCopyMemory, and
// OpAtomic* are determined by their pointer parameter or parameters.
// Pointers are always (correctly) typed and so the address and number of
// consecutive locations are fully determined by the pointer.
//
// - A pointer value orginates as one of few cases:
//
// - OpVariable for an interface object or an array of them: image,
// buffer (UBO or SSBO), sampler, sampled-image, push-constant, input
// variable, output variable. The execution environment is responsible for
// allocating the correct amount of storage for these, and for ensuring
// each resource bound to such a variable is big enough to contain the
// SPIR-V pointee type of the variable.
//
// - OpVariable for a non-interface object. These are variables in
// Workgroup, Private, and Function storage classes. The compiler ensures
// the underlying allocation is big enough to store the entire SPIR-V
// pointee type of the variable.
//
// - An OpFunctionParameter. This always maps to a pointer parameter to an
// OpFunctionCall.
//
// - In logical addressing mode, these are severely limited:
// "Any pointer operand to an OpFunctionCall must be:
// - a memory object declaration, or
// - a pointer to an element in an array that is a memory object
// declaration, where the element type is OpTypeSampler or OpTypeImage"
//
// - This has an important simplifying consequence:
//
// - When looking for a pointer to the structure containing a runtime
// array, you begin with a pointer to the runtime array and trace
// backward in the function. You never have to trace back beyond
// your function call boundary. So you can't take a partial access
// chain into an SSBO, then pass that pointer into a function. So
// we don't resort to using fat pointers to compute array length.
// We can trace back to a pointer to the containing structure,
// and use that in an OpArrayLength instruction. (The structure type
// gives us the member index of the runtime array.)
//
// - Otherwise, the pointer type fully encodes the range of valid
// addresses. In particular, the type of a pointer to an aggregate
// value fully encodes the range of indices when indexing into
// that aggregate.
//
// - The pointer is the result of an access chain instruction. We clamp
// indices contributing to address calculations. As noted above, the
// valid ranges are either bound by the length of a runtime array, or
// by the type of the base pointer. The length of a runtime array is
// the result of an OpArrayLength instruction acting on the pointer of
// the containing structure as noted above.
//
// - Access chain indices are always treated as signed, so:
// - Clamp the upper bound at the signed integer maximum.
// - Use SClamp for all clamping.
//
// - TODO(dneto): OpImageTexelPointer:
// - Clamp coordinate to the image size returned by OpImageQuerySize
// - If multi-sampled, clamp the sample index to the count returned by
// OpImageQuerySamples.
// - If not multi-sampled, set the sample index to 0.
//
// - Rely on the external validator to check that pointers are only
// used by the instructions as above.
//
// - Handles OpTypeRuntimeArray
// Track pointer back to original resource (pointer to struct), so we can
// query the runtime array size.
//
#include "graphics_robust_access_pass.h"
#include <algorithm>
#include <cstring>
#include <functional>
#include <initializer_list>
#include <limits>
#include <utility>
#include "constants.h"
#include "def_use_manager.h"
#include "function.h"
#include "ir_context.h"
#include "module.h"
#include "pass.h"
#include "source/diagnostic.h"
#include "source/util/make_unique.h"
#include "spirv-tools/libspirv.h"
#include "spirv/unified1/GLSL.std.450.h"
#include "spirv/unified1/spirv.h"
#include "type_manager.h"
#include "types.h"
namespace spvtools {
namespace opt {
using opt::Instruction;
using opt::Operand;
using spvtools::MakeUnique;
GraphicsRobustAccessPass::GraphicsRobustAccessPass() : module_status_() {}
Pass::Status GraphicsRobustAccessPass::Process() {
module_status_ = PerModuleState();
ProcessCurrentModule();
auto result = module_status_.failed
? Status::Failure
: (module_status_.modified ? Status::SuccessWithChange
: Status::SuccessWithoutChange);
return result;
}
spvtools::DiagnosticStream GraphicsRobustAccessPass::Fail() {
module_status_.failed = true;
// We don't really have a position, and we'll ignore the result.
return std::move(
spvtools::DiagnosticStream({}, consumer(), "", SPV_ERROR_INVALID_BINARY)
<< name() << ": ");
}
spv_result_t GraphicsRobustAccessPass::IsCompatibleModule() {
auto* feature_mgr = context()->get_feature_mgr();
if (!feature_mgr->HasCapability(SpvCapabilityShader))
return Fail() << "Can only process Shader modules";
if (feature_mgr->HasCapability(SpvCapabilityVariablePointers))
return Fail() << "Can't process modules with VariablePointers capability";
if (feature_mgr->HasCapability(SpvCapabilityVariablePointersStorageBuffer))
return Fail() << "Can't process modules with VariablePointersStorageBuffer "
"capability";
if (feature_mgr->HasCapability(SpvCapabilityRuntimeDescriptorArrayEXT)) {
// These have a RuntimeArray outside of Block-decorated struct. There
// is no way to compute the array length from within SPIR-V.
return Fail() << "Can't process modules with RuntimeDescriptorArrayEXT "
"capability";
}
{
auto* inst = context()->module()->GetMemoryModel();
const auto addressing_model = inst->GetSingleWordOperand(0);
if (addressing_model != SpvAddressingModelLogical)
return Fail() << "Addressing model must be Logical. Found "
<< inst->PrettyPrint();
}
return SPV_SUCCESS;
}
spv_result_t GraphicsRobustAccessPass::ProcessCurrentModule() {
auto err = IsCompatibleModule();
if (err != SPV_SUCCESS) return err;
ProcessFunction fn = [this](opt::Function* f) { return ProcessAFunction(f); };
module_status_.modified |= context()->ProcessReachableCallTree(fn);
// Need something here. It's the price we pay for easier failure paths.
return SPV_SUCCESS;
}
bool GraphicsRobustAccessPass::ProcessAFunction(opt::Function* function) {
// Ensure that all pointers computed inside a function are within bounds.
// Find the access chains in this block before trying to modify them.
std::vector<Instruction*> access_chains;
std::vector<Instruction*> image_texel_pointers;
for (auto& block : *function) {
for (auto& inst : block) {
switch (inst.opcode()) {
case SpvOpAccessChain:
case SpvOpInBoundsAccessChain:
access_chains.push_back(&inst);
break;
case SpvOpImageTexelPointer:
image_texel_pointers.push_back(&inst);
break;
default:
break;
}
}
}
for (auto* inst : access_chains) {
ClampIndicesForAccessChain(inst);
if (module_status_.failed) return module_status_.modified;
}
for (auto* inst : image_texel_pointers) {
if (SPV_SUCCESS != ClampCoordinateForImageTexelPointer(inst)) break;
}
return module_status_.modified;
}
void GraphicsRobustAccessPass::ClampIndicesForAccessChain(
Instruction* access_chain) {
Instruction& inst = *access_chain;
auto* constant_mgr = context()->get_constant_mgr();
auto* def_use_mgr = context()->get_def_use_mgr();
auto* type_mgr = context()->get_type_mgr();
const bool have_int64_cap =
context()->get_feature_mgr()->HasCapability(SpvCapabilityInt64);
// Replaces one of the OpAccessChain index operands with a new value.
// Updates def-use analysis.
auto replace_index = [&inst, def_use_mgr](uint32_t operand_index,
Instruction* new_value) {
inst.SetOperand(operand_index, {new_value->result_id()});
def_use_mgr->AnalyzeInstUse(&inst);
return SPV_SUCCESS;
};
// Replaces one of the OpAccesssChain index operands with a clamped value.
// Replace the operand at |operand_index| with the value computed from
// signed_clamp(%old_value, %min_value, %max_value). It also analyzes
// the new instruction and records that them module is modified.
// Assumes %min_value is signed-less-or-equal than %max_value. (All callees
// use 0 for %min_value).
auto clamp_index = [&inst, type_mgr, this, &replace_index](
uint32_t operand_index, Instruction* old_value,
Instruction* min_value, Instruction* max_value) {
auto* clamp_inst =
MakeSClampInst(*type_mgr, old_value, min_value, max_value, &inst);
return replace_index(operand_index, clamp_inst);
};
// Ensures the specified index of access chain |inst| has a value that is
// at most |count| - 1. If the index is already a constant value less than
// |count| then no change is made.
auto clamp_to_literal_count =
[&inst, this, &constant_mgr, &type_mgr, have_int64_cap, &replace_index,
&clamp_index](uint32_t operand_index, uint64_t count) -> spv_result_t {
Instruction* index_inst =
this->GetDef(inst.GetSingleWordOperand(operand_index));
const auto* index_type =
type_mgr->GetType(index_inst->type_id())->AsInteger();
assert(index_type);
const auto index_width = index_type->width();
if (count <= 1) {
// Replace the index with 0.
return replace_index(operand_index, GetValueForType(0, index_type));
}
uint64_t maxval = count - 1;
// Compute the bit width of a viable type to hold |maxval|.
// Look for a bit width, up to 64 bits wide, to fit maxval.
uint32_t maxval_width = index_width;
while ((maxval_width < 64) && (0 != (maxval >> maxval_width))) {
maxval_width *= 2;
}
// Determine the type for |maxval|.
analysis::Integer signed_type_for_query(maxval_width, true);
auto* maxval_type =
type_mgr->GetRegisteredType(&signed_type_for_query)->AsInteger();
// Access chain indices are treated as signed, so limit the maximum value
// of the index so it will always be positive for a signed clamp operation.
maxval = std::min(maxval, ((uint64_t(1) << (maxval_width - 1)) - 1));
if (index_width > 64) {
return this->Fail() << "Can't handle indices wider than 64 bits, found "
"constant index with "
<< index_width << " bits as index number "
<< operand_index << " of access chain "
<< inst.PrettyPrint();
}
// Split into two cases: the current index is a constant, or not.
// If the index is a constant then |index_constant| will not be a null
// pointer. (If index is an |OpConstantNull| then it |index_constant| will
// not be a null pointer.) Since access chain indices must be scalar
// integers, this can't be a spec constant.
if (auto* index_constant = constant_mgr->GetConstantFromInst(index_inst)) {
auto* int_index_constant = index_constant->AsIntConstant();
int64_t value = 0;
// OpAccessChain indices are treated as signed. So get the signed
// constant value here.
if (index_width <= 32) {
value = int64_t(int_index_constant->GetS32BitValue());
} else if (index_width <= 64) {
value = int_index_constant->GetS64BitValue();
}
if (value < 0) {
return replace_index(operand_index, GetValueForType(0, index_type));
} else if (uint64_t(value) <= maxval) {
// Nothing to do.
return SPV_SUCCESS;
} else {
// Replace with maxval.
assert(count > 0); // Already took care of this case above.
return replace_index(operand_index,
GetValueForType(maxval, maxval_type));
}
} else {
// Generate a clamp instruction.
assert(maxval >= 1);
assert(index_width <= 64); // Otherwise, already returned above.
if (index_width >= 64 && !have_int64_cap) {
// An inconsistent module.
return Fail() << "Access chain index is wider than 64 bits, but Int64 "
"is not declared: "
<< index_inst->PrettyPrint();
}
// Widen the index value if necessary
if (maxval_width > index_width) {
// Find the wider type. We only need this case if a constant array
// bound is too big.
// From how we calculated maxval_width, widening won't require adding
// the Int64 capability.
assert(have_int64_cap || maxval_width <= 32);
if (!have_int64_cap && maxval_width >= 64) {
// Be defensive, but this shouldn't happen.
return this->Fail()
<< "Clamping index would require adding Int64 capability. "
<< "Can't clamp 32-bit index " << operand_index
<< " of access chain " << inst.PrettyPrint();
}
index_inst = WidenInteger(index_type->IsSigned(), maxval_width,
index_inst, &inst);
}
// Finally, clamp the index.
return clamp_index(operand_index, index_inst,
GetValueForType(0, maxval_type),
GetValueForType(maxval, maxval_type));
}
return SPV_SUCCESS;
};
// Ensures the specified index of access chain |inst| has a value that is at
// most the value of |count_inst| minus 1, where |count_inst| is treated as an
// unsigned integer. This can log a failure.
auto clamp_to_count = [&inst, this, &constant_mgr, &clamp_to_literal_count,
&clamp_index,
&type_mgr](uint32_t operand_index,
Instruction* count_inst) -> spv_result_t {
Instruction* index_inst =
this->GetDef(inst.GetSingleWordOperand(operand_index));
const auto* index_type =
type_mgr->GetType(index_inst->type_id())->AsInteger();
const auto* count_type =
type_mgr->GetType(count_inst->type_id())->AsInteger();
assert(index_type);
if (const auto* count_constant =
constant_mgr->GetConstantFromInst(count_inst)) {
uint64_t value = 0;
const auto width = count_constant->type()->AsInteger()->width();
if (width <= 32) {
value = count_constant->AsIntConstant()->GetU32BitValue();
} else if (width <= 64) {
value = count_constant->AsIntConstant()->GetU64BitValue();
} else {
return this->Fail() << "Can't handle indices wider than 64 bits, found "
"constant index with "
<< index_type->width() << "bits";
}
return clamp_to_literal_count(operand_index, value);
} else {
// Widen them to the same width.
const auto index_width = index_type->width();
const auto count_width = count_type->width();
const auto target_width = std::max(index_width, count_width);
// UConvert requires the result type to have 0 signedness. So enforce
// that here.
auto* wider_type = index_width < count_width ? count_type : index_type;
if (index_type->width() < target_width) {
// Access chain indices are treated as signed integers.
index_inst = WidenInteger(true, target_width, index_inst, &inst);
} else if (count_type->width() < target_width) {
// Assume type sizes are treated as unsigned.
count_inst = WidenInteger(false, target_width, count_inst, &inst);
}
// Compute count - 1.
// It doesn't matter if 1 is signed or unsigned.
auto* one = GetValueForType(1, wider_type);
auto* count_minus_1 = InsertInst(
&inst, SpvOpISub, type_mgr->GetId(wider_type), TakeNextId(),
{{SPV_OPERAND_TYPE_ID, {count_inst->result_id()}},
{SPV_OPERAND_TYPE_ID, {one->result_id()}}});
auto* zero = GetValueForType(0, wider_type);
// Make sure we clamp to an upper bound that is at most the signed max
// for the target type.
const uint64_t max_signed_value =
((uint64_t(1) << (target_width - 1)) - 1);
// Use unsigned-min to ensure that the result is always non-negative.
// That ensures we satisfy the invariant for SClamp, where the "min"
// argument we give it (zero), is no larger than the third argument.
auto* upper_bound =
MakeUMinInst(*type_mgr, count_minus_1,
GetValueForType(max_signed_value, wider_type), &inst);
// Now clamp the index to this upper bound.
return clamp_index(operand_index, index_inst, zero, upper_bound);
}
return SPV_SUCCESS;
};
const Instruction* base_inst = GetDef(inst.GetSingleWordInOperand(0));
const Instruction* base_type = GetDef(base_inst->type_id());
Instruction* pointee_type = GetDef(base_type->GetSingleWordInOperand(1));
// Walk the indices from earliest to latest, replacing indices with a
// clamped value, and updating the pointee_type. The order matters for
// the case when we have to compute the length of a runtime array. In
// that the algorithm relies on the fact that that the earlier indices
// have already been clamped.
const uint32_t num_operands = inst.NumOperands();
for (uint32_t idx = 3; !module_status_.failed && idx < num_operands; ++idx) {
const uint32_t index_id = inst.GetSingleWordOperand(idx);
Instruction* index_inst = GetDef(index_id);
switch (pointee_type->opcode()) {
case SpvOpTypeMatrix: // Use column count
case SpvOpTypeVector: // Use component count
{
const uint32_t count = pointee_type->GetSingleWordOperand(2);
clamp_to_literal_count(idx, count);
pointee_type = GetDef(pointee_type->GetSingleWordOperand(1));
} break;
case SpvOpTypeArray: {
// The array length can be a spec constant, so go through the general
// case.
Instruction* array_len = GetDef(pointee_type->GetSingleWordOperand(2));
clamp_to_count(idx, array_len);
pointee_type = GetDef(pointee_type->GetSingleWordOperand(1));
} break;
case SpvOpTypeStruct: {
// SPIR-V requires the index to be an OpConstant.
// We need to know the index literal value so we can compute the next
// pointee type.
if (index_inst->opcode() != SpvOpConstant ||
!constant_mgr->GetConstantFromInst(index_inst)
->type()
->AsInteger()) {
Fail() << "Member index into struct is not a constant integer: "
<< index_inst->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES)
<< "\nin access chain: "
<< inst.PrettyPrint(SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
return;
}
const auto num_members = pointee_type->NumInOperands();
const auto* index_constant =
constant_mgr->GetConstantFromInst(index_inst);
// Get the sign-extended value, since access index is always treated as
// signed.
const auto index_value = index_constant->GetSignExtendedValue();
if (index_value < 0 || index_value >= num_members) {
Fail() << "Member index " << index_value
<< " is out of bounds for struct type: "
<< pointee_type->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES)
<< "\nin access chain: "
<< inst.PrettyPrint(SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
return;
}
pointee_type = GetDef(pointee_type->GetSingleWordInOperand(
static_cast<uint32_t>(index_value)));
// No need to clamp this index. We just checked that it's valid.
} break;
case SpvOpTypeRuntimeArray: {
auto* array_len = MakeRuntimeArrayLengthInst(&inst, idx);
if (!array_len) { // We've already signaled an error.
return;
}
clamp_to_count(idx, array_len);
if (module_status_.failed) return;
pointee_type = GetDef(pointee_type->GetSingleWordOperand(1));
} break;
default:
Fail() << " Unhandled pointee type for access chain "
<< pointee_type->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
}
}
}
uint32_t GraphicsRobustAccessPass::GetGlslInsts() {
if (module_status_.glsl_insts_id == 0) {
// This string serves double-duty as raw data for a string and for a vector
// of 32-bit words
const char glsl[] = "GLSL.std.450\0\0\0\0";
const size_t glsl_str_byte_len = 16;
// Use an existing import if we can.
for (auto& inst : context()->module()->ext_inst_imports()) {
const auto& name_words = inst.GetInOperand(0).words;
if (0 == std::strncmp(reinterpret_cast<const char*>(name_words.data()),
glsl, glsl_str_byte_len)) {
module_status_.glsl_insts_id = inst.result_id();
}
}
if (module_status_.glsl_insts_id == 0) {
// Make a new import instruction.
module_status_.glsl_insts_id = TakeNextId();
std::vector<uint32_t> words(glsl_str_byte_len / sizeof(uint32_t));
std::memcpy(words.data(), glsl, glsl_str_byte_len);
auto import_inst = MakeUnique<Instruction>(
context(), SpvOpExtInstImport, 0, module_status_.glsl_insts_id,
std::initializer_list<Operand>{
Operand{SPV_OPERAND_TYPE_LITERAL_STRING, std::move(words)}});
Instruction* inst = import_inst.get();
context()->module()->AddExtInstImport(std::move(import_inst));
module_status_.modified = true;
context()->AnalyzeDefUse(inst);
// Reanalyze the feature list, since we added an extended instruction
// set improt.
context()->get_feature_mgr()->Analyze(context()->module());
}
}
return module_status_.glsl_insts_id;
}
opt::Instruction* opt::GraphicsRobustAccessPass::GetValueForType(
uint64_t value, const analysis::Integer* type) {
auto* mgr = context()->get_constant_mgr();
assert(type->width() <= 64);
std::vector<uint32_t> words;
words.push_back(uint32_t(value));
if (type->width() > 32) {
words.push_back(uint32_t(value >> 32u));
}
const auto* constant = mgr->GetConstant(type, words);
return mgr->GetDefiningInstruction(
constant, context()->get_type_mgr()->GetTypeInstruction(type));
}
opt::Instruction* opt::GraphicsRobustAccessPass::WidenInteger(
bool sign_extend, uint32_t bit_width, Instruction* value,
Instruction* before_inst) {
analysis::Integer unsigned_type_for_query(bit_width, false);
auto* type_mgr = context()->get_type_mgr();
auto* unsigned_type = type_mgr->GetRegisteredType(&unsigned_type_for_query);
auto type_id = context()->get_type_mgr()->GetId(unsigned_type);
auto conversion_id = TakeNextId();
auto* conversion = InsertInst(
before_inst, (sign_extend ? SpvOpSConvert : SpvOpUConvert), type_id,
conversion_id, {{SPV_OPERAND_TYPE_ID, {value->result_id()}}});
return conversion;
}
Instruction* GraphicsRobustAccessPass::MakeUMinInst(
const analysis::TypeManager& tm, Instruction* x, Instruction* y,
Instruction* where) {
// Get IDs of instructions we'll be referencing. Evaluate them before calling
// the function so we force a deterministic ordering in case both of them need
// to take a new ID.
const uint32_t glsl_insts_id = GetGlslInsts();
uint32_t smin_id = TakeNextId();
const auto xwidth = tm.GetType(x->type_id())->AsInteger()->width();
const auto ywidth = tm.GetType(y->type_id())->AsInteger()->width();
assert(xwidth == ywidth);
(void)xwidth;
(void)ywidth;
auto* smin_inst = InsertInst(
where, SpvOpExtInst, x->type_id(), smin_id,
{
{SPV_OPERAND_TYPE_ID, {glsl_insts_id}},
{SPV_OPERAND_TYPE_EXTENSION_INSTRUCTION_NUMBER, {GLSLstd450UMin}},
{SPV_OPERAND_TYPE_ID, {x->result_id()}},
{SPV_OPERAND_TYPE_ID, {y->result_id()}},
});
return smin_inst;
}
Instruction* GraphicsRobustAccessPass::MakeSClampInst(
const analysis::TypeManager& tm, Instruction* x, Instruction* min,
Instruction* max, Instruction* where) {
// Get IDs of instructions we'll be referencing. Evaluate them before calling
// the function so we force a deterministic ordering in case both of them need
// to take a new ID.
const uint32_t glsl_insts_id = GetGlslInsts();
uint32_t clamp_id = TakeNextId();
const auto xwidth = tm.GetType(x->type_id())->AsInteger()->width();
const auto minwidth = tm.GetType(min->type_id())->AsInteger()->width();
const auto maxwidth = tm.GetType(max->type_id())->AsInteger()->width();
assert(xwidth == minwidth);
assert(xwidth == maxwidth);
(void)xwidth;
(void)minwidth;
(void)maxwidth;
auto* clamp_inst = InsertInst(
where, SpvOpExtInst, x->type_id(), clamp_id,
{
{SPV_OPERAND_TYPE_ID, {glsl_insts_id}},
{SPV_OPERAND_TYPE_EXTENSION_INSTRUCTION_NUMBER, {GLSLstd450SClamp}},
{SPV_OPERAND_TYPE_ID, {x->result_id()}},
{SPV_OPERAND_TYPE_ID, {min->result_id()}},
{SPV_OPERAND_TYPE_ID, {max->result_id()}},
});
return clamp_inst;
}
Instruction* GraphicsRobustAccessPass::MakeRuntimeArrayLengthInst(
Instruction* access_chain, uint32_t operand_index) {
// The Index parameter to the access chain at |operand_index| is indexing
// *into* the runtime-array. To get the number of elements in the runtime
// array we need a pointer to the Block-decorated struct that contains the
// runtime array. So conceptually we have to go 2 steps backward in the
// access chain. The two steps backward might forces us to traverse backward
// across multiple dominating instructions.
auto* type_mgr = context()->get_type_mgr();
// How many access chain indices do we have to unwind to find the pointer
// to the struct containing the runtime array?
uint32_t steps_remaining = 2;
// Find or create an instruction computing the pointer to the structure
// containing the runtime array.
// Walk backward through pointer address calculations until we either get
// to exactly the right base pointer, or to an access chain instruction
// that we can replicate but truncate to compute the address of the right
// struct.
Instruction* current_access_chain = access_chain;
Instruction* pointer_to_containing_struct = nullptr;
while (steps_remaining > 0) {
switch (current_access_chain->opcode()) {
case SpvOpCopyObject:
// Whoops. Walk right through this one.
current_access_chain =
GetDef(current_access_chain->GetSingleWordInOperand(0));
break;
case SpvOpAccessChain:
case SpvOpInBoundsAccessChain: {
const int first_index_operand = 3;
// How many indices in this access chain contribute to getting us
// to an element in the runtime array?
const auto num_contributing_indices =
current_access_chain == access_chain
? operand_index - (first_index_operand - 1)
: current_access_chain->NumInOperands() - 1 /* skip the base */;
Instruction* base =
GetDef(current_access_chain->GetSingleWordInOperand(0));
if (num_contributing_indices == steps_remaining) {
// The base pointer points to the structure.
pointer_to_containing_struct = base;
steps_remaining = 0;
break;
} else if (num_contributing_indices < steps_remaining) {
// Peel off the index and keep going backward.
steps_remaining -= num_contributing_indices;
current_access_chain = base;
} else {
// This access chain has more indices than needed. Generate a new
// access chain instruction, but truncating the list of indices.
const int base_operand = 2;
// We'll use the base pointer and the indices up to but not including
// the one indexing into the runtime array.
Instruction::OperandList ops;
// Use the base pointer
ops.push_back(current_access_chain->GetOperand(base_operand));
const uint32_t num_indices_to_keep =
num_contributing_indices - steps_remaining - 1;
for (uint32_t i = 0; i <= num_indices_to_keep; i++) {
ops.push_back(
current_access_chain->GetOperand(first_index_operand + i));
}
// Compute the type of the result of the new access chain. Start at
// the base and walk the indices in a forward direction.
auto* constant_mgr = context()->get_constant_mgr();
std::vector<uint32_t> indices_for_type;
for (uint32_t i = 0; i < ops.size() - 1; i++) {
uint32_t index_for_type_calculation = 0;
Instruction* index =
GetDef(current_access_chain->GetSingleWordOperand(
first_index_operand + i));
if (auto* index_constant =
constant_mgr->GetConstantFromInst(index)) {
// We only need 32 bits. For the type calculation, it's sufficient
// to take the zero-extended value. It only matters for the struct
// case, and struct member indices are unsigned.
index_for_type_calculation =
uint32_t(index_constant->GetZeroExtendedValue());
} else {
// Indexing into a variably-sized thing like an array. Use 0.
index_for_type_calculation = 0;
}
indices_for_type.push_back(index_for_type_calculation);
}
auto* base_ptr_type = type_mgr->GetType(base->type_id())->AsPointer();
auto* base_pointee_type = base_ptr_type->pointee_type();
auto* new_access_chain_result_pointee_type =
type_mgr->GetMemberType(base_pointee_type, indices_for_type);
const uint32_t new_access_chain_type_id = type_mgr->FindPointerToType(
type_mgr->GetId(new_access_chain_result_pointee_type),
base_ptr_type->storage_class());
// Create the instruction and insert it.
const auto new_access_chain_id = TakeNextId();
auto* new_access_chain =
InsertInst(current_access_chain, current_access_chain->opcode(),
new_access_chain_type_id, new_access_chain_id, ops);
pointer_to_containing_struct = new_access_chain;
steps_remaining = 0;
break;
}
} break;
default:
Fail() << "Unhandled access chain in logical addressing mode passes "
"through "
<< current_access_chain->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_SHOW_BYTE_OFFSET |
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
return nullptr;
}
}
assert(pointer_to_containing_struct);
auto* pointee_type =
type_mgr->GetType(pointer_to_containing_struct->type_id())
->AsPointer()
->pointee_type();
auto* struct_type = pointee_type->AsStruct();
const uint32_t member_index_of_runtime_array =
uint32_t(struct_type->element_types().size() - 1);
// Create the length-of-array instruction before the original access chain,
// but after the generation of the pointer to the struct.
const auto array_len_id = TakeNextId();
analysis::Integer uint_type_for_query(32, false);
auto* uint_type = type_mgr->GetRegisteredType(&uint_type_for_query);
auto* array_len = InsertInst(
access_chain, SpvOpArrayLength, type_mgr->GetId(uint_type), array_len_id,
{{SPV_OPERAND_TYPE_ID, {pointer_to_containing_struct->result_id()}},
{SPV_OPERAND_TYPE_LITERAL_INTEGER, {member_index_of_runtime_array}}});
return array_len;
}
spv_result_t GraphicsRobustAccessPass::ClampCoordinateForImageTexelPointer(
opt::Instruction* image_texel_pointer) {
// TODO(dneto): Write tests for this code.
// TODO(dneto): Use signed-clamp
return SPV_SUCCESS;
// Example:
// %texel_ptr = OpImageTexelPointer %texel_ptr_type %image_ptr %coord
// %sample
//
// We want to clamp %coord components between vector-0 and the result
// of OpImageQuerySize acting on the underlying image. So insert:
// %image = OpLoad %image_type %image_ptr
// %query_size = OpImageQuerySize %query_size_type %image
//
// For a multi-sampled image, %sample is the sample index, and we need
// to clamp it between zero and the number of samples in the image.
// %sample_count = OpImageQuerySamples %uint %image
// %max_sample_index = OpISub %uint %sample_count %uint_1
// For non-multi-sampled images, the sample index must be constant zero.
auto* def_use_mgr = context()->get_def_use_mgr();
auto* type_mgr = context()->get_type_mgr();
auto* constant_mgr = context()->get_constant_mgr();
auto* image_ptr = GetDef(image_texel_pointer->GetSingleWordInOperand(0));
auto* image_ptr_type = GetDef(image_ptr->type_id());
auto image_type_id = image_ptr_type->GetSingleWordInOperand(1);
auto* image_type = GetDef(image_type_id);
auto* coord = GetDef(image_texel_pointer->GetSingleWordInOperand(1));
auto* samples = GetDef(image_texel_pointer->GetSingleWordInOperand(2));
// We will modify the module, at least by adding image query instructions.
module_status_.modified = true;
// Declare the ImageQuery capability if the module doesn't already have it.
auto* feature_mgr = context()->get_feature_mgr();
if (!feature_mgr->HasCapability(SpvCapabilityImageQuery)) {
auto cap = MakeUnique<Instruction>(
context(), SpvOpCapability, 0, 0,
std::initializer_list<Operand>{
{SPV_OPERAND_TYPE_CAPABILITY, {SpvCapabilityImageQuery}}});
def_use_mgr->AnalyzeInstDefUse(cap.get());
context()->AddCapability(std::move(cap));
feature_mgr->Analyze(context()->module());
}
// OpImageTexelPointer is used to translate a coordinate and sample index
// into an address for use with an atomic operation. That is, it may only
// used with what Vulkan calls a "storage image"
// (OpTypeImage parameter Sampled=2).
// Note: A storage image never has a level-of-detail associated with it.
// Constraints on the sample id:
// - Only 2D images can be multi-sampled: OpTypeImage parameter MS=1
// only if Dim=2D.
// - Non-multi-sampled images (OpTypeImage parameter MS=0) must use
// sample ID to a constant 0.
// The coordinate is treated as unsigned, and should be clamped against the
// image "size", returned by OpImageQuerySize. (Note: OpImageQuerySizeLod
// is only usable with a sampled image, i.e. its image type has Sampled=1).
// Determine the result type for the OpImageQuerySize.
// For non-arrayed images:
// non-Cube:
// - Always the same as the coordinate type
// Cube:
// - Use all but the last component of the coordinate (which is the face
// index from 0 to 5).
// For arrayed images (in Vulkan the Dim is 1D, 2D, or Cube):
// non-Cube:
// - A vector with the components in the coordinate, and one more for
// the layer index.
// Cube:
// - The same as the coordinate type: 3-element integer vector.
// - The third component from the size query is the layer count.
// - The third component in the texel pointer calculation is
// 6 * layer + face, where 0 <= face < 6.
// Cube: Use all but the last component of the coordinate (which is the face
// index from 0 to 5).
const auto dim = SpvDim(image_type->GetSingleWordInOperand(1));
const bool arrayed = image_type->GetSingleWordInOperand(3) == 1;
const bool multisampled = image_type->GetSingleWordInOperand(4) != 0;
const auto query_num_components = [dim, arrayed, this]() -> int {
const int arrayness_bonus = arrayed ? 1 : 0;
int num_coords = 0;
switch (dim) {
case SpvDimBuffer:
case SpvDim1D:
num_coords = 1;
break;
case SpvDimCube:
// For cube, we need bounds for x, y, but not face.
case SpvDimRect:
case SpvDim2D:
num_coords = 2;
break;
case SpvDim3D:
num_coords = 3;
break;
case SpvDimSubpassData:
case SpvDimMax:
return Fail() << "Invalid image dimension for OpImageTexelPointer: "
<< int(dim);
break;
}
return num_coords + arrayness_bonus;
}();
const auto* coord_component_type = [type_mgr, coord]() {
const analysis::Type* coord_type = type_mgr->GetType(coord->type_id());
if (auto* vector_type = coord_type->AsVector()) {
return vector_type->element_type()->AsInteger();
}
return coord_type->AsInteger();
}();
// For now, only handle 32-bit case for coordinates.
if (!coord_component_type) {
return Fail() << " Coordinates for OpImageTexelPointer are not integral: "
<< image_texel_pointer->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
}
if (coord_component_type->width() != 32) {
return Fail() << " Expected OpImageTexelPointer coordinate components to "
"be 32-bits wide. They are "
<< coord_component_type->width() << " bits. "
<< image_texel_pointer->PrettyPrint(
SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
}
const auto* query_size_type =
[type_mgr, coord_component_type,
query_num_components]() -> const analysis::Type* {
if (query_num_components == 1) return coord_component_type;
analysis::Vector proposed(coord_component_type, query_num_components);
return type_mgr->GetRegisteredType(&proposed);
}();
const uint32_t image_id = TakeNextId();
auto* image =
InsertInst(image_texel_pointer, SpvOpLoad, image_type_id, image_id,
{{SPV_OPERAND_TYPE_ID, {image_ptr->result_id()}}});
const uint32_t query_size_id = TakeNextId();
auto* query_size =
InsertInst(image_texel_pointer, SpvOpImageQuerySize,
type_mgr->GetTypeInstruction(query_size_type), query_size_id,
{{SPV_OPERAND_TYPE_ID, {image->result_id()}}});
auto* component_1 = constant_mgr->GetConstant(coord_component_type, {1});
const uint32_t component_1_id =
constant_mgr->GetDefiningInstruction(component_1)->result_id();
auto* component_0 = constant_mgr->GetConstant(coord_component_type, {0});
const uint32_t component_0_id =
constant_mgr->GetDefiningInstruction(component_0)->result_id();
// If the image is a cube array, then the last component of the queried
// size is the layer count. In the query, we have to accomodate folding
// in the face index ranging from 0 through 5. The inclusive upper bound
// on the third coordinate therefore is multiplied by 6.
auto* query_size_including_faces = query_size;
if (arrayed && (dim == SpvDimCube)) {
// Multiply the last coordinate by 6.
auto* component_6 = constant_mgr->GetConstant(coord_component_type, {6});
const uint32_t component_6_id =
constant_mgr->GetDefiningInstruction(component_6)->result_id();
assert(query_num_components == 3);
auto* multiplicand = constant_mgr->GetConstant(
query_size_type, {component_1_id, component_1_id, component_6_id});
auto* multiplicand_inst =
constant_mgr->GetDefiningInstruction(multiplicand);
const auto query_size_including_faces_id = TakeNextId();
query_size_including_faces = InsertInst(
image_texel_pointer, SpvOpIMul,
type_mgr->GetTypeInstruction(query_size_type),
query_size_including_faces_id,
{{SPV_OPERAND_TYPE_ID, {query_size_including_faces->result_id()}},
{SPV_OPERAND_TYPE_ID, {multiplicand_inst->result_id()}}});
}
// Make a coordinate-type with all 1 components.
auto* coordinate_1 =
query_num_components == 1
? component_1
: constant_mgr->GetConstant(
query_size_type,
std::vector<uint32_t>(query_num_components, component_1_id));
// Make a coordinate-type with all 1 components.
auto* coordinate_0 =
query_num_components == 0
? component_0
: constant_mgr->GetConstant(
query_size_type,
std::vector<uint32_t>(query_num_components, component_0_id));
const uint32_t query_max_including_faces_id = TakeNextId();
auto* query_max_including_faces = InsertInst(
image_texel_pointer, SpvOpISub,
type_mgr->GetTypeInstruction(query_size_type),
query_max_including_faces_id,
{{SPV_OPERAND_TYPE_ID, {query_size_including_faces->result_id()}},
{SPV_OPERAND_TYPE_ID,
{constant_mgr->GetDefiningInstruction(coordinate_1)->result_id()}}});
// Clamp the coordinate
auto* clamp_coord = MakeSClampInst(
*type_mgr, coord, constant_mgr->GetDefiningInstruction(coordinate_0),
query_max_including_faces, image_texel_pointer);
image_texel_pointer->SetInOperand(1, {clamp_coord->result_id()});
// Clamp the sample index
if (multisampled) {
// Get the sample count via OpImageQuerySamples
const auto query_samples_id = TakeNextId();
auto* query_samples = InsertInst(
image_texel_pointer, SpvOpImageQuerySamples,
constant_mgr->GetDefiningInstruction(component_0)->type_id(),
query_samples_id, {{SPV_OPERAND_TYPE_ID, {image->result_id()}}});
const auto max_samples_id = TakeNextId();
auto* max_samples = InsertInst(image_texel_pointer, SpvOpImageQuerySamples,
query_samples->type_id(), max_samples_id,
{{SPV_OPERAND_TYPE_ID, {query_samples_id}},
{SPV_OPERAND_TYPE_ID, {component_1_id}}});
auto* clamp_samples = MakeSClampInst(
*type_mgr, samples, constant_mgr->GetDefiningInstruction(coordinate_0),
max_samples, image_texel_pointer);
image_texel_pointer->SetInOperand(2, {clamp_samples->result_id()});
} else {
// Just replace it with 0. Don't even check what was there before.
image_texel_pointer->SetInOperand(2, {component_0_id});
}
def_use_mgr->AnalyzeInstUse(image_texel_pointer);
return SPV_SUCCESS;
}
opt::Instruction* GraphicsRobustAccessPass::InsertInst(
opt::Instruction* where_inst, SpvOp opcode, uint32_t type_id,
uint32_t result_id, const Instruction::OperandList& operands) {
module_status_.modified = true;
auto* result = where_inst->InsertBefore(
MakeUnique<Instruction>(context(), opcode, type_id, result_id, operands));
context()->get_def_use_mgr()->AnalyzeInstDefUse(result);
auto* basic_block = context()->get_instr_block(where_inst);
context()->set_instr_block(result, basic_block);
return result;
}
} // namespace opt
} // namespace spvtools
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