Fix a pair of issues that caused an infinite loop in reassociate.

Terrifyingly, one of them is a mishandling of floating point vectors
in Constant::isZero().  How exactly this issue survived this long
is beyond me.

llvm-svn: 253655

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 550d9a89a65..b237c913dcf 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -68,6 +68,12 @@ bool Constant::isZeroValue() const {
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
     return CFP->isZero();
 
+  // Equivalent for a vector of -0.0's.
+  if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
+    if (ConstantFP *SplatCFP = dyn_cast_or_null<ConstantFP>(CV->getSplatValue()))
+      if (SplatCFP && SplatCFP->isZero())
+        return true;
+
   // Otherwise, just use +0.0.
   return isNullValue();
 }