[InstCombine] Fix a vector splat handling bug in transformZExtICmp.

We were using an i1 type and then zero extending to a vector. Instead just create the 0/1 directly as a ConstantInt with the correct type. No need to ask ConstantExpr to zero extend for us.

This bug is a bit tricky to hit because it requires us to visit a zext of an icmp that would normally be simplified to true/false, but that icmp hasnt' been visited yet. In the test case this zext and icmp were created by visiting a udiv and due to worklist ordering we got to the zext first.

Fixes PR34841.

llvm-svn: 314971

1 files changed, 1 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index f7be0f9bc3f..5e4fd8c2656 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -818,9 +818,7 @@ Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, ZExtInst &CI,
         if (!Op1CV->isNullValue() && (*Op1CV != KnownZeroMask)) {
           // (X&4) == 2 --> false
           // (X&4) != 2 --> true
-          Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()),
-                                           isNE);
-          Res = ConstantExpr::getZExt(Res, CI.getType());
+          Constant *Res = ConstantInt::get(CI.getType(), isNE);
           return replaceInstUsesWith(CI, Res);
         }