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Update WebAssembly Branch Hinting proposal

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The main change is the section name, which is now 'metadata.code.branch_hint'.
The binary format has also a couple of minor changes.
Semantics remain unchanged.

Change-Id: I056c9f672ae494979e8ea55266fa766139b71d38
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3487788
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79292}
This commit is contained in:
Yuri Iozzelli 2022-02-25 15:38:03 +01:00 committed by V8 LUCI CQ
parent a3361beec4
commit 29f1c13849
3 changed files with 21 additions and 19 deletions
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6
src/wasm/function-body-decoder-impl.h
View File

@ -2234,6 +2234,7 @@ class WasmFullDecoder : public WasmDecoder<validate, decoding_mode> {
DCHECK_LE(this->pc_, this->end_);
DCHECK_EQ(this->num_locals(), 0);
locals_offset_ = this->pc_offset();
this->InitializeLocalsFromSig();
uint32_t params_count = static_cast<uint32_t>(this->num_locals());
uint32_t locals_length;
@ -2340,7 +2341,7 @@ class WasmFullDecoder : public WasmDecoder<validate, decoding_mode> {
}
uint32_t pc_relative_offset() const {
return this->pc_offset() - first_instruction_offset;
return this->pc_offset() - locals_offset_;
}
void DecodeFunctionBody() {
@ -2374,7 +2375,6 @@ class WasmFullDecoder : public WasmDecoder<validate, decoding_mode> {
CALL_INTERFACE_IF_OK_AND_REACHABLE(StartFunctionBody, c);
}
first_instruction_offset = this->pc_offset();
// Decode the function body.
while (this->pc_ < this->end_) {
// Most operations only grow the stack by at least one element (unary and
@ -2407,7 +2407,7 @@ class WasmFullDecoder : public WasmDecoder<validate, decoding_mode> {
}
private:
uint32_t first_instruction_offset = 0;
uint32_t locals_offset_ = 0;
Interface interface_;
// The value stack, stored as individual pointers for maximum performance.

14
src/wasm/module-decoder.cc
View File

@ -36,7 +36,7 @@ namespace {
constexpr char kNameString[] = "name";
constexpr char kSourceMappingURLString[] = "sourceMappingURL";
constexpr char kCompilationHintsString[] = "compilationHints";
constexpr char kBranchHintsString[] = "branchHints";
constexpr char kBranchHintsString[] = "metadata.code.branch_hint";
constexpr char kDebugInfoString[] = ".debug_info";
constexpr char kExternalDebugInfoString[] = "external_debug_info";
@ -1345,11 +1345,6 @@ class ModuleDecoderImpl : public Decoder {
break;
}
last_func_idx = func_idx;
uint8_t reserved = inner.consume_u8("reserved byte");
if (reserved != 0x0) {
inner.errorf("Invalid reserved byte: %#x", reserved);
break;
}
uint32_t num_hints = inner.consume_u32v("number of hints");
BranchHintMap func_branch_hints;
TRACE("DecodeBranchHints[%d] module+%d\n", func_idx,
@ -1357,13 +1352,18 @@ class ModuleDecoderImpl : public Decoder {
// Keep track of the previous branch offset to validate the ordering
int64_t last_br_off = -1;
for (uint32_t j = 0; j < num_hints; ++j) {
uint32_t br_dir = inner.consume_u32v("branch direction");
uint32_t br_off = inner.consume_u32v("branch instruction offset");
if (int64_t(br_off) <= last_br_off) {
inner.errorf("Invalid branch offset: %d", br_off);
break;
}
last_br_off = br_off;
uint32_t data_size = inner.consume_u32v("data size");
if (data_size != 1) {
inner.errorf("Invalid data size: %#x. Expected 1.", data_size);
break;
}
uint32_t br_dir = inner.consume_u8("branch direction");
TRACE("DecodeBranchHints[%d][%d] module+%d\n", func_idx, br_off,
static_cast<int>(inner.pc() - inner.start()));
WasmBranchHint hint;

20
test/unittests/wasm/module-decoder-unittest.cc
View File

@ -76,9 +76,11 @@ namespace module_decoder_unittest {
'H', 'i', 'n', 't', 's'), \
ADD_COUNT(__VA_ARGS__))
#define SECTION_BRANCH_HINTS(...) \
SECTION(Unknown, \
ADD_COUNT('b', 'r', 'a', 'n', 'c', 'h', 'H', 'i', 'n', 't', 's'), \
#define SECTION_BRANCH_HINTS(...) \
SECTION(Unknown, \
ADD_COUNT('m', 'e', 't', 'a', 'd', 'a', 't', 'a', '.', 'c', 'o', \
'd', 'e', '.', 'b', 'r', 'a', 'n', 'c', 'h', '_', 'h', \
'i', 'n', 't'), \
__VA_ARGS__)
#define FAIL_IF_NO_EXPERIMENTAL_EH(data) \
@ -2228,10 +2230,10 @@ TEST_F(WasmModuleVerifyTest, BranchHinting) {
WASM_FEATURE_SCOPE(branch_hinting);
static const byte data[] = {
TYPE_SECTION(1, SIG_ENTRY_v_v), FUNCTION_SECTION(2, 0, 0),
SECTION_BRANCH_HINTS(ENTRY_COUNT(2), 0 /*func_index*/, 0 /*reserved*/,
ENTRY_COUNT(1), 1 /*likely*/, 2 /* if offset*/,
1 /*func_index*/, 0 /*reserved*/, ENTRY_COUNT(1),
0 /*unlikely*/, 4 /* br_if offset*/),
SECTION_BRANCH_HINTS(ENTRY_COUNT(2), 0 /*func_index*/, ENTRY_COUNT(1),
3 /* if offset*/, 1 /*reserved*/, 1 /*likely*/,
1 /*func_index*/, ENTRY_COUNT(1),
5 /* br_if offset*/, 1 /*reserved*/, 0 /*unlikely*/),
SECTION(Code, ENTRY_COUNT(2),
ADD_COUNT(0, /*no locals*/
WASM_IF(WASM_I32V_1(1), WASM_NOP), WASM_END),
@ -2243,9 +2245,9 @@ TEST_F(WasmModuleVerifyTest, BranchHinting) {
EXPECT_EQ(2u, result.value()->branch_hints.size());
EXPECT_EQ(WasmBranchHint::kLikely,
result.value()->branch_hints[0].GetHintFor(2));
result.value()->branch_hints[0].GetHintFor(3));
EXPECT_EQ(WasmBranchHint::kUnlikely,
result.value()->branch_hints[1].GetHintFor(4));
result.value()->branch_hints[1].GetHintFor(5));
}
class WasmSignatureDecodeTest : public TestWithZone {