Index: lib/Transforms/Scalar/Reassociate.cpp
===================================================================
--- lib/Transforms/Scalar/Reassociate.cpp
+++ lib/Transforms/Scalar/Reassociate.cpp
@@ -897,10 +897,13 @@
 /// version of the value is returned, and BI is left pointing at the instruction
 /// that should be processed next by the reassociation pass.
 static Value *NegateValue(Value *V, Instruction *BI) {
-  if (ConstantFP *C = dyn_cast<ConstantFP>(V))
-    return ConstantExpr::getFNeg(C);
-  if (Constant *C = dyn_cast<Constant>(V))
+  if (Constant *C = dyn_cast<Constant>(V)) {
+    if (C->getType()->isFPOrFPVectorTy()) {
+      return ConstantExpr::getFNeg(C);
+    }
     return ConstantExpr::getNeg(C);
+  }
+
 
   // We are trying to expose opportunity for reassociation.  One of the things
   // that we want to do to achieve this is to push a negation as deep into an
Index: test/Transforms/Reassociate/undef.ll
===================================================================
--- /dev/null
+++ test/Transforms/Reassociate/undef.ll
@@ -0,0 +1,21 @@
+; RUN: opt -reassociate %s
+
+; Reassociate pass use to crash on these example
+
+
+define float @undef1() {
+wrapper_entry:
+  %0 = fadd fast float undef, undef
+  %1 = fsub fast float undef, %0
+  %2 = fadd fast float undef, %1
+  ret float %2
+}
+
+define void @undef2() {
+wrapper_entry:
+  %0 = fadd fast float undef, undef
+  %1 = fadd fast float %0, 1.000000e+00
+  %2 = fsub fast float %0, %1
+  %3 = fmul fast float %2, 2.000000e+00
+  unreachable
+}