Use APInt's umul_ov instead of rolling our own overflow detection.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128380 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index b5fd0b9..875e9ca 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -487,14 +487,15 @@
APInt RHSKnownOne(BitWidth, 0);
ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
- // Get the largest possible values for each operand, extended to be large
- // enough so that every possible product of two BitWidth-sized ints fits.
- APInt LHSMax = (~LHSKnownZero).zext(BitWidth*2);
- APInt RHSMax = (~RHSKnownZero).zext(BitWidth*2);
+ // Get the largest possible values for each operand.
+ APInt LHSMax = ~LHSKnownZero;
+ APInt RHSMax = ~RHSKnownZero;
// If multiplying the maximum values does not overflow then we can turn
// this into a plain NUW mul.
- if ((LHSMax * RHSMax).getActiveBits() <= BitWidth) {
+ bool Overflow;
+ LHSMax.umul_ov(RHSMax, Overflow);
+ if (!Overflow) {
Value *Mul = Builder->CreateNUWMul(LHS, RHS, "umul_with_overflow");
Constant *V[] = {
UndefValue::get(LHS->getType()),