Reviewers: ulan, jochen,
Message:
This doesn't actually make anything measurably faster, but it does tidy
things
up.
Description:
ARM64: Move sign-extension to load instructions.
The SXTW extend mode is usually free when used in a load or store
operand, but it can slightly increase the latency of an arithmetic
instruction. This patch optimises some address calculations accordingly:
- PrepareKeyedExternalArrayOperand.
- BuildSeqStringOperand.
- DoStringCharFromCode.
BUG=
Please review this at https://codereview.chromium.org/247443002/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+28, -47 lines):
M src/arm64/lithium-arm64.cc
M src/arm64/lithium-codegen-arm64.cc
Index: src/arm64/lithium-arm64.cc
diff --git a/src/arm64/lithium-arm64.cc b/src/arm64/lithium-arm64.cc
index
8682e2b82fc190cce90c98b6c2a01f7d1635b9fa..8323405b46e80414b41991fbc80bf6b9404ac81b
100644
--- a/src/arm64/lithium-arm64.cc
+++ b/src/arm64/lithium-arm64.cc
@@ -1665,9 +1665,10 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed*
instr) {
ASSERT(instr->key()->representation().IsSmiOrInteger32());
ElementsKind elements_kind = instr->elements_kind();
LOperand* elements = UseRegister(instr->elements());
- LOperand* key = UseRegisterOrConstantAtStart(instr->key());
if (!instr->is_typed_elements()) {
+ LOperand* key = UseRegisterOrConstantAtStart(instr->key());
+
if (instr->representation().IsDouble()) {
LOperand* temp = (!instr->key()->IsConstant() ||
instr->RequiresHoleCheck())
@@ -1695,6 +1696,7 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed*
instr) {
(instr->representation().IsDouble() &&
IsDoubleOrFloatElementsKind(instr->elements_kind())));
+ LOperand* key = UseRegisterOrConstant(instr->key());
LOperand* temp = instr->key()->IsConstant() ? NULL : TempRegister();
LInstruction* result = DefineAsRegister(
new(zone()) LLoadKeyedExternal(elements, key, temp));
@@ -2187,7 +2189,6 @@ LInstruction*
LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
LOperand* temp = NULL;
LOperand* elements = NULL;
LOperand* val = NULL;
- LOperand* key = UseRegisterOrConstantAtStart(instr->key());
if (!instr->is_typed_elements() &&
instr->value()->representation().IsTagged() &&
@@ -2211,16 +2212,19 @@ LInstruction*
LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
instr->elements()->representation().IsTagged()) ||
(instr->is_external() &&
instr->elements()->representation().IsExternal()));
+ LOperand* key = UseRegisterOrConstant(instr->key());
return new(zone()) LStoreKeyedExternal(elements, key, val, temp);
} else if (instr->value()->representation().IsDouble()) {
ASSERT(instr->elements()->representation().IsTagged());
+ LOperand* key = UseRegisterOrConstantAtStart(instr->key());
return new(zone()) LStoreKeyedFixedDouble(elements, key, val, temp);
} else {
ASSERT(instr->elements()->representation().IsTagged());
ASSERT(instr->value()->representation().IsSmiOrTagged() ||
instr->value()->representation().IsInteger32());
+ LOperand* key = UseRegisterOrConstantAtStart(instr->key());
return new(zone()) LStoreKeyedFixed(elements, key, val, temp);
}
}
Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc
b/src/arm64/lithium-codegen-arm64.cc
index
f8f06cfe8257a387c1b4f71990e1b90962f0c851..969af2b06da77b0645b32e5f3310a78d249b3d23
100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -3333,51 +3333,28 @@ MemOperand
LCodeGen::PrepareKeyedExternalArrayOperand(
ElementsKind elements_kind,
int additional_index) {
int element_size_shift = ElementsKindToShiftSize(elements_kind);
- int additional_offset = IsFixedTypedArrayElementsKind(elements_kind)
- ? FixedTypedArrayBase::kDataOffset - kHeapObjectTag
- : 0;
+ int additional_offset = additional_index << element_size_shift;
+ if (IsFixedTypedArrayElementsKind(elements_kind)) {
+ additional_offset += FixedTypedArrayBase::kDataOffset - kHeapObjectTag;
+ }
if (key_is_constant) {
- int base_offset = ((constant_key + additional_index) <<
element_size_shift);
- return MemOperand(base, base_offset + additional_offset);
+ int key_offset = constant_key << element_size_shift;
+ return MemOperand(base, key_offset + additional_offset);
}
- if (additional_index == 0) {
- if (key_is_smi) {
- // Key is smi: untag, and scale by element size.
- __ Add(scratch, base, Operand::UntagSmiAndScale(key,
element_size_shift));
- return MemOperand(scratch, additional_offset);
- } else {
- // Key is not smi, and element size is not byte: scale by element
size.
- if (additional_offset == 0) {
- return MemOperand(base, key, SXTW, element_size_shift);
- } else {
- __ Add(scratch, base, Operand(key, SXTW, element_size_shift));
- return MemOperand(scratch, additional_offset);
- }
- }
- } else {
- // TODO(all): Try to combine these cases a bit more intelligently.
- if (additional_offset == 0) {
- if (key_is_smi) {
- __ SmiUntag(scratch, key);
- __ Add(scratch.W(), scratch.W(), additional_index);
- } else {
- __ Add(scratch.W(), key.W(), additional_index);
- }
- return MemOperand(base, scratch, LSL, element_size_shift);
- } else {
- if (key_is_smi) {
- __ Add(scratch, base,
- Operand::UntagSmiAndScale(key, element_size_shift));
- } else {
- __ Add(scratch, base, Operand(key, SXTW, element_size_shift));
- }
- return MemOperand(
- scratch,
- (additional_index << element_size_shift) + additional_offset);
- }
+ if (key_is_smi) {
+ __ Add(scratch, base, Operand::UntagSmiAndScale(key,
element_size_shift));
+ return MemOperand(scratch, additional_offset);
}
+
+ if (additional_offset == 0) {
+ return MemOperand(base, key, SXTW, element_size_shift);
+ }
+
+ ASSERT(!AreAliased(scratch, key));
+ __ Add(scratch, base, additional_offset);
+ return MemOperand(scratch, key, SXTW, element_size_shift);
}
@@ -4673,13 +4650,13 @@ MemOperand LCodeGen::BuildSeqStringOperand(Register
string,
return FieldMemOperand(string, SeqString::kHeaderSize + offset);
}
+ __ Add(temp, string, SeqString::kHeaderSize - kHeapObjectTag);
if (encoding == String::ONE_BYTE_ENCODING) {
- __ Add(temp, string, Operand(ToRegister32(index), SXTW));
+ return MemOperand(temp, ToRegister32(index), SXTW);
} else {
STATIC_ASSERT(kUC16Size == 2);
- __ Add(temp, string, Operand(ToRegister32(index), SXTW, 1));
+ return MemOperand(temp, ToRegister32(index), SXTW, 1);
}
- return FieldMemOperand(temp, SeqString::kHeaderSize);
}
@@ -5410,8 +5387,8 @@ void
LCodeGen::DoStringCharFromCode(LStringCharFromCode* instr) {
__ Cmp(char_code, String::kMaxOneByteCharCode);
__ B(hi, deferred->entry());
__ LoadRoot(result, Heap::kSingleCharacterStringCacheRootIndex);
- __ Add(result, result, Operand(char_code, SXTW, kPointerSizeLog2));
- __ Ldr(result, FieldMemOperand(result, FixedArray::kHeaderSize));
+ __ Add(result, result, FixedArray::kHeaderSize - kHeapObjectTag);
+ __ Ldr(result, MemOperand(result, char_code, SXTW, kPointerSizeLog2));
__ CompareRoot(result, Heap::kUndefinedValueRootIndex);
__ B(eq, deferred->entry());
__ Bind(deferred->exit());
--
--
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