Make InstCombineCasts.cpp:OptimizeIntToFloatBitCast endian safe.
The OptimizeIntToFloatBitCast converts shift-truncate sequences
into extractelement operations. The computation of the element
index to be used in the resulting operation is currently only
correct for little-endian targets.
This commit fixes the element index computation to be correct
for big-endian targets as well. If the target byte order is
unknown, the optimization cannot be performed at all.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178031 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index d162223..2ee1278 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1610,6 +1610,9 @@
/// OptimizeIntToFloatBitCast - See if we can optimize an integer->float/double
/// bitcast. The various long double bitcasts can't get in here.
static Instruction *OptimizeIntToFloatBitCast(BitCastInst &CI,InstCombiner &IC){
+ // We need to know the target byte order to perform this optimization.
+ if (!IC.getDataLayout()) return 0;
+
Value *Src = CI.getOperand(0);
Type *DestTy = CI.getType();
@@ -1631,7 +1634,10 @@
VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
}
- return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(0));
+ unsigned Elt = 0;
+ if (IC.getDataLayout()->isBigEndian())
+ Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1;
+ return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
}
}
@@ -1653,6 +1659,8 @@
}
unsigned Elt = ShAmt->getZExtValue() / DestWidth;
+ if (IC.getDataLayout()->isBigEndian())
+ Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1 - Elt;
return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
}
}