InstCombine: Improve the result bitvect type when folding (cmp pred (load (gep GV, i)) C) to a bit test.
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
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 32fdb9b..a4e117e 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -443,20 +443,29 @@
}
- // 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;