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InstCombine: Improve the result bitvect type when folding (cmp pred (load (gep GV, i)) C) to a bit test.

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The original code used i32, and i64 if legal. This introduced unneeded
casts when they aren't legal, or when the index variable i has another
type. In order of preference: try to use i's type; use the smallest
fitting legal type (using an added DataLayout method); default to i32.
A testcase checks that this works when the index gep operand is i16.

Patch by : Ahmed Bougacha <ahmed.bougacha@gmail.com>
Reviewed by : Duncan

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177712 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnaud A. de Grandmaison
2013-03-22 08:25:01 +00:00
parent 9b294d4056
commit 2be921adc4
4 changed files with 43 additions and 11 deletions
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31
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@@ -443,20 +443,29 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
}
// If a 32-bit or 64-bit magic bitvector captures the entire comparison state
// If a magic bitvector captures the entire comparison state
// of this load, replace it with computation that does:
// ((magic_cst >> i) & 1) != 0
if (ArrayElementCount <= 32 ||
(TD && ArrayElementCount <= 64 && TD->isLegalInteger(64))) {
Type *Ty;
if (ArrayElementCount <= 32)
{
Type *Ty = 0;
// Look for an appropriate type:
// - The type of Idx if the magic fits
// - The smallest fitting legal type if we have a DataLayout
// - Default to i32
if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
Ty = Idx->getType();
else if (TD)
Ty = TD->getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
else if (ArrayElementCount <= 32)
Ty = Type::getInt32Ty(Init->getContext());
else
Ty = Type::getInt64Ty(Init->getContext());
Value *V = Builder->CreateIntCast(Idx, Ty, false);
V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V);
return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
if (Ty != 0) {
Value *V = Builder->CreateIntCast(Idx, Ty, false);
V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V);
return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
}
}
return 0;