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[wasm][turbofan] Load 32-bit values more efficiently

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When loading a 32-bit value from the stack, just load 32 bit and
zero-extend them into the target register, instead of loading the full
64 bits.

As there are things to fix (see https://crbug.com/1356461), we only
enable this optimization for Wasm for now.

R=jkummerow@chromium.org

Bug: chromium:1395604, chromium:1356461, v8:13581
Change-Id: Ibdd2d80704973362906aec9b38faa762d3b43f3f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4097424
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84796}
This commit is contained in:
Clemens Backes 2022-12-12 17:20:08 +01:00 committed by V8 LUCI CQ
parent 50961e7032
commit a38209949f
1 changed files with 16 additions and 1 deletions
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17
src/compiler/backend/x64/code-generator-x64.cc
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@ -5335,7 +5335,22 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
case MoveType::kStackToRegister: {
Operand src = g.ToOperand(source);
if (source->IsStackSlot()) {
__ movq(g.ToRegister(destination), src);
MachineRepresentation mr =
LocationOperand::cast(source)->representation();
const bool is_32_bit = mr == MachineRepresentation::kWord32 ||
mr == MachineRepresentation::kCompressed ||
mr == MachineRepresentation::kCompressedPointer;
// TODO(13581): Fix this for other code kinds (see
// https://crbug.com/1356461).
if (code_kind() == CodeKind::WASM_FUNCTION && is_32_bit) {
// When we need only 32 bits, move only 32 bits. Benefits:
// - Save a byte here and there (depending on the destination
// register; "movl eax, ..." is smaller than "movq rax, ...").
// - Safeguard against accidental decompression of compressed slots.
__ movl(g.ToRegister(destination), src);
} else {
__ movq(g.ToRegister(destination), src);
}
} else {
DCHECK(source->IsFPStackSlot());
XMMRegister dst = g.ToDoubleRegister(destination);