[InstCombine] Pass a proper context instruction to all of the calls into InstSimplify

Summary: This matches the behavior we already had for compares and makes us consistent everywhere.

Reviewers: dberlin, hfinkel, spatel

Reviewed By: dberlin

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33604

llvm-svn: 305049
diff --git a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
index 5c9daeb..5dbf1e8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -880,7 +880,7 @@
 // PHINode simplification
 //
 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
-  if (Value *V = SimplifyInstruction(&PN, SQ))
+  if (Value *V = SimplifyInstruction(&PN, SQ.getWithInstruction(&PN)))
     return replaceInstUsesWith(PN, V);
 
   if (Instruction *Result = FoldPHIArgZextsIntoPHI(PN))