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[csa] ChangeUint32ToTagged doesn't need to double-check for overflow.

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Bug: v8:8015
Change-Id: Iabb051be94768e5ca570a8fa5128a3dbf66065da
Reviewed-on: https://chromium-review.googlesource.com/1221194
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55829}
This commit is contained in:
Benedikt Meurer 2018-09-12 16:02:16 +02:00 committed by Commit Bot
parent c97cb459d0
commit 3c082741a4
2 changed files with 6 additions and 18 deletions
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21
src/code-stub-assembler.cc
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@ -5044,28 +5044,13 @@ TNode<Number> CodeStubAssembler::ChangeUint32ToTagged(
if_join(this);
TVARIABLE(Number, var_result);
// If {value} > 2^31 - 1, we need to store it in a HeapNumber.
Branch(Uint32LessThan(Int32Constant(Smi::kMaxValue), value), &if_overflow,
Branch(Uint32LessThan(Uint32Constant(Smi::kMaxValue), value), &if_overflow,
&if_not_overflow);
BIND(&if_not_overflow);
{
if (SmiValuesAre32Bits()) {
var_result =
SmiTag(ReinterpretCast<IntPtrT>(ChangeUint32ToUint64(value)));
} else {
DCHECK(SmiValuesAre31Bits());
// If tagging {value} results in an overflow, we need to use a HeapNumber
// to represent it.
// TODO(tebbi): This overflow can never happen.
TNode<PairT<Int32T, BoolT>> pair = Int32AddWithOverflow(
UncheckedCast<Int32T>(value), UncheckedCast<Int32T>(value));
TNode<BoolT> overflow = Projection<1>(pair);
GotoIf(overflow, &if_overflow);
TNode<IntPtrT> almost_tagged_value =
ChangeInt32ToIntPtr(Projection<0>(pair));
var_result = BitcastWordToTaggedSigned(almost_tagged_value);
}
// The {value} is definitely in valid Smi range.
var_result = SmiTag(Signed(ChangeUint32ToWord(value)));
}
Goto(&if_join);

3
src/compiler/code-assembler.h
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@ -698,6 +698,9 @@ class V8_EXPORT_PRIVATE CodeAssembler {
TNode<Int32T> Int32Constant(int32_t value);
TNode<Int64T> Int64Constant(int64_t value);
TNode<IntPtrT> IntPtrConstant(intptr_t value);
TNode<Uint32T> Uint32Constant(uint32_t value) {
return Unsigned(Int32Constant(bit_cast<int32_t>(value)));
}
TNode<Number> NumberConstant(double value);
TNode<Smi> SmiConstant(Smi* value);
TNode<Smi> SmiConstant(int value);