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[wasm] All accesses of bytes in memory are aligned.

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It makes no sense to check if unaligned accesses of bytes in memory are
allowed, since these accesses are always aligned. There was a problem
on mips that we created an UnalignedLoad(Int8), which was, however, not
implemented in the mips instruction selector.

R=clemensh@chromium.org

Change-Id: I20369e078e3c24942aa90c2bd3333d9881de0072
Reviewed-on: https://chromium-review.googlesource.com/463006
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44277}
This commit is contained in:
Andreas Haas 2017-03-30 11:02:11 +02:00 committed by Commit Bot
parent c066623ed7
commit fc0caf6de8
2 changed files with 6 additions and 2 deletions
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2
src/compiler/machine-operator.h
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@ -184,6 +184,8 @@ class V8_EXPORT_PRIVATE MachineOperatorBuilder final
bool IsUnalignedSupported(const Vector<MachineType>& unsupported,
const MachineType& machineType,
uint8_t alignment) const {
// All accesses of bytes in memory are aligned.
DCHECK_NE(machineType.representation(), MachineRepresentation::kWord8);
if (unalignedSupport_ == kFullSupport) {
return true;
} else if (unalignedSupport_ == kNoSupport) {

6
src/compiler/wasm-compiler.cc
View File

@ -3017,7 +3017,8 @@ Node* WasmGraphBuilder::LoadMem(wasm::ValueType type, MachineType memtype,
BoundsCheckMem(memtype, index, offset, position);
}
if (jsgraph()->machine()->UnalignedLoadSupported(memtype, alignment)) {
if (memtype.representation() == MachineRepresentation::kWord8 ||
jsgraph()->machine()->UnalignedLoadSupported(memtype, alignment)) {
if (FLAG_wasm_trap_handler && V8_TRAP_HANDLER_SUPPORTED) {
DCHECK(FLAG_wasm_guard_pages);
Node* position_node = jsgraph()->Int32Constant(position);
@ -3072,7 +3073,8 @@ Node* WasmGraphBuilder::StoreMem(MachineType memtype, Node* index,
val = BuildChangeEndianness(val, memtype);
#endif
if (jsgraph()->machine()->UnalignedStoreSupported(memtype, alignment)) {
if (memtype.representation() == MachineRepresentation::kWord8 ||
jsgraph()->machine()->UnalignedStoreSupported(memtype, alignment)) {
if (FLAG_wasm_trap_handler && V8_TRAP_HANDLER_SUPPORTED) {
Node* position_node = jsgraph()->Int32Constant(position);
store = graph()->NewNode(