The existing spirv-opt `DebugInfoManager::AddDebugValueForDecl()` sets
the scope and line info of the new added DebugValue using the scope and
line of DebugDeclare. This is wrong because only a single DebugDeclare
must exist under a scope while we have to add DebugValue for all the
places where the variable's value is updated. Therefore, we have to set
the scope and line of DebugValue based on the places of the variable
updates.
This bug makes
https://github.com/google/amber/blob/main/tests/cases/debugger_hlsl_shadowed_vars.amber
fail. This commit fixes the bug.
spirv-opt has a bug that `DebugInfoManager::AddDebugValueWithIndex()` does not
preserve `Indexes` operands of
[DebugValue](https://www.khronos.org/registry/spir-v/specs/unified1/OpenCL.DebugInfo.100.html#DebugValue).
It has to preserve all of those `Indexes` operands, but it preserves only the first index
operand.
This PR removes `DebugInfoManager::AddDebugValueWithIndex()` and lets the spirv-opt
use `DebugInfoManager::AddDebugValueForDecl()`.
`DebugInfoManager::AddDebugValueForDecl()` preserves the Indexes operand correctly.
This fixes https://github.com/KhronosGroup/SPIRV-Tools/issues/3873.
In the presence of variable pointers, the reaching definition may be
another pointer. For example, the following fragment:
%2 = OpVariable %_ptr_Input_float Input
%11 = OpVariable %_ptr_Function__ptr_Input_float Function
OpStore %11 %2
%12 = OpLoad %_ptr_Input_float %11
%13 = OpLoad %float %12
corresponds to the pseudo-code:
layout(location = 0) in flat float *%2
float %13;
float *%12;
float **%11;
*%11 = %2;
%12 = *%11;
%13 = *%12;
which ultimately, should correspond to:
%13 = *%2;
During rewriting, the pointer %12 is found to be replaceable by %2.
However, when processing the load %13 = *%12, the type of %12's reaching
definition is another float pointer (%2), instead of a float value.
When this happens, we need to continue looking up the reaching definition
chain until we get to a float value or a non-target var (i.e. a variable
that cannot be SSA replaced, like %2 in this case since it is a function
argument).
For some cases, we have DebugDecl invisible to a value assignment, but
the value assignment information is important i.e., debugger cannot inspect
the variable without the information. For example, a parameter of an inlined
function must have its value assignment i.e., argument passing out of its
function scope. If we simply remove DebugDecl because it is invisible to the
argument passing, we cannot inspec the variable.
This PR
- Adds DebugValue for DebugDecl invisible to a value assignment. We use
the value of the variable in the basic block that contains DebugDecl, which is
found by ssa-rewrite. If the value instruction does not dominate DebugDecl,
we use the value of the variable in the immediate dominator of the basic block.
- Checks the visibility of DebugDecl for Phi value assignment based on the
all value operands of the Phi. Since Phi just references multiple values from
multiple basic blocks, scopes of value operands must be regarded as the scope
of the Phi.
For each local variable, ssa-rewrite should remove its DebugDeclare
if and only if it is replaced by any number of DebugValues for store
and phi instructions.
For example, when we have two variables `a` whose DebugDeclare
will be replaced to DebugValues by ssa-rewrite pass and `b` whose
DebugDeclare will not be replaced, we have to remove only DebugDeclare
for `a`, not `b`.
1. Set the debug scope and line information for the new replacement
instructions.
2. Replace DebugDeclare and DebugValue if their OpVariable or value
operands are replaced by scalars. It uses 'Indexes' operand of
DebugValue. For example,
struct S { int a; int b;}
S foo; // before scalar replacement
int foo_a; // after scalar replacement
int foo_b;
DebugDeclare %dbg_foo %foo %null_expr // before
DebugValue %dbg_foo %foo_a %Deref_expr 0 // after
DebugValue %dbg_foo %foo_b %Deref_expr 1 // means Value(foo.members[1]) == Deref(%foo_b)
When the pass replaces the local variable `OpVariable` ids to their
corresponding pointers, we have to update operands of DebugValue or
DebugDeclare instructions.
Add OpenCL.DebugInfo.100 `DebugValue` instructions for store
and phi instructions of local variables to provide the debugger with
the updated values of local variables correctly.
* Handle id overflow in the ssa rewriter.
Remove LocalSSAElim pass at the same time. It does the same thing as the SSARewrite pass. Then even share almost all of the same code.
Fixes crbug.com/997246
When a phi candidate is marked as trivial, we are suppose to update all
of its uses to the reference the value that it is being folded to.
However, the code updates the uses misses `defs_at_block_`. So at a
later time, the id for the trivial phi can reemerge.
Fixes#2744
If there are multiple edges to a basic block, then the ssa rewriter will
create OpPhi instructions with duplicate entries. This is invalid, and
it is fixed in this commit.
Fixes#2202.
Added documentation to the ir context to indicates that TakeNextId()
returns 0 when the max id is reached. TODOs were added to each call
sight so that we know where we have to start to handle this case.
Handle id overflow in |SplitLoopHeader|.
Handle id overflow in |GetOrCreatePreHeaderBlock|.
Handle failure to create preheader in LICM.
Part of https://github.com/KhronosGroup/SPIRV-Tools/issues/1841.
* Copy decorations when creating new ids.
When creating a new value based on an old value, we need to copy the
decorations to the new id. This change does this in 3 places:
1) The variable holding the return value of the function generated by
merge return should get decorations from the function.
2) The results of the OpPhi instructions should get decorations from the
variable they are replacing in the ssa writer.
3) In local access chain convert the intermediate struct (result of
OpCompositeInsert) generated for the store replacement should get its
decorations from the variable being stored to.
Fixes#1787.
Currently the IRContext is passed into the Pass::Process method. It is
then up to the individual pass to store the context into the context_
variable. This CL changes the Run method to store the context before
calling Process which no-longer receives the context as a parameter.
This CL moves the files in opt/ to consistenly be under the opt::
namespace. This frees up the ir:: namespace so it can be used to make a
shared ir represenation.
From the test case, the slice of the CFG that is interesting for the bug
is
25
|
v
30
|
v
31<-+
| |
v |
34--+
1. In block 25, we have a Phi candidate for %f with arguments
%47 = Phi[%float_0, %0]. This merges %float_0 and a yet unknown
argument from the external loop backedge.
2. We are now processing block 34:
i. The load %35 = OpLoad %f triggers a Phi candidate to be placed in
block 31.
ii. The Phi candidate %50 = Phi needs two arguments. The one coming
from block 30 is %47. But the one coming from block 34 (which we
are now processing and have marked sealed), finds %50 itself as
the reaching def for %f.
3. This wrongfully marks %50 as a copy-of Phi, which ultimately makes
both %47 and %50 copy-of Phis that get eliminated.
This pass replaces the load/store elimination passes. It implements the
SSA re-writing algorithm proposed in
Simple and Efficient Construction of Static Single Assignment Form.
Braun M., Buchwald S., Hack S., Leißa R., Mallon C., Zwinkau A. (2013)
In: Jhala R., De Bosschere K. (eds)
Compiler Construction. CC 2013.
Lecture Notes in Computer Science, vol 7791.
Springer, Berlin, Heidelberg
https://link.springer.com/chapter/10.1007/978-3-642-37051-9_6
In contrast to common eager algorithms based on dominance and dominance
frontier information, this algorithm works backwards from load operations.
When a target variable is loaded, it queries the variable's reaching
definition. If the reaching definition is unknown at the current location,
it searches backwards in the CFG, inserting Phi instructions at join points
in the CFG along the way until it finds the desired store instruction.
The algorithm avoids repeated lookups using memoization.
For reducible CFGs, which are a superset of the structured CFGs in SPIRV,
this algorithm is proven to produce minimal SSA. That is, it inserts the
minimal number of Phi instructions required to ensure the SSA property, but
some Phi instructions may be dead
(https://en.wikipedia.org/wiki/Static_single_assignment_form).
