Teach InstructionSimplify about phi nodes. I chose to have it simply

offload the work to hasConstantValue rather than do something more
complicated (such handling mutually recursive phis) because (1) it is
not clear it is worth it; and (2) if it is worth it, maybe such logic
would be better placed in hasConstantValue.  Adjust some GVN tests
which are now cleaned up much further (eg: all phi nodes are removed).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119043 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 5 insertions, 2 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index b3e817a..210399d 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -699,6 +699,8 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
     SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
     return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
   }
+  case Instruction::PHI:
+    return cast<PHINode>(I)->hasConstantValue();
   }
 }
 
diff --git a/lib/Transforms/InstCombine/InstCombinePHI.cpp b/lib/Transforms/InstCombine/InstCombinePHI.cpp
index f7fc62f..736473d 100644
--- a/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "InstCombine.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/STLExtras.h"
@@ -731,8 +732,8 @@ Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
   // If LCSSA is around, don't mess with Phi nodes
   if (MustPreserveLCSSA) return 0;
-  
-  if (Value *V = PN.hasConstantValue())
+
+  if (Value *V = SimplifyInstruction(&PN, TD))
     return ReplaceInstUsesWith(PN, V);
 
   // If all PHI operands are the same operation, pull them through the PHI,