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

4 files changed, 24 insertions, 22 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index b3e817a750..210399d729 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 f7fc62f9dc..736473db1d 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,
diff --git a/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll b/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
index 13d1bd1b7e..14cb91b531 100644
--- a/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
+++ b/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
@@ -1,30 +1,33 @@
-; RUN: opt < %s -basicaa -gvn -S | grep {tmp17625.* = phi i32. }
-; RUN: opt < %s -basicaa -gvn -S | grep {tmp17631.* = phi i32. }
+; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
 
-@last = external global [65 x i32*]		; <[65 x i32*]*> [#uses=1]
+@last = external global [65 x i32*]
 
 define i32 @NextRootMove(i32 %wtm) {
-cond_next95:		; preds = %cond_true85, %cond_true79, %cond_true73, %bb68
-	%tmp17618 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4		; <i32*> [#uses=0]
+entry:
+	%tmp17618 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
+; CHECK: entry:
+; CHECK-NEXT: %tmp17618 = load
+; CHECK-NOT: load
+; CHECK-NOT: phi
 	br label %cond_true116
 
-cond_true116:		; preds = %cond_true111
+cond_true116:
 	br i1 false, label %cond_true128, label %cond_true145
 
-cond_true128:		; preds = %cond_true121
-	%tmp17625 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4		; <i32*> [#uses=0]
+cond_true128:
+	%tmp17625 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
 	br i1 false, label %bb98.backedge, label %return.loopexit
 
-bb98.backedge:		; preds = %bb171, %cond_true145, %cond_true128
+bb98.backedge:
 	br label %cond_true116
 
-cond_true145:		; preds = %cond_false
-	%tmp17631 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4		; <i32*> [#uses=0]
+cond_true145:
+	%tmp17631 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
 	br i1 false, label %bb98.backedge, label %return.loopexit
 
-return.loopexit:		; preds = %bb171, %cond_true145, %cond_true128
+return.loopexit:
 	br label %return
 
-return:		; preds = %return.loopexit, %cond_next95, %cond_true85
+return:
 	ret i32 0
 }
diff --git a/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll b/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
index c408daa58d..d6e1c6b76d 100644
--- a/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
+++ b/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
@@ -1,5 +1,8 @@
 ; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
 
+; CHECK-NOT: load
+; CHECK-NOT: phi
+
 define i8* @cat(i8* %s1, ...) nounwind {
 entry:
   br i1 undef, label %bb, label %bb3
@@ -29,18 +32,11 @@ bb10:                                             ; preds = %bb8
   br label %bb11
 
 bb11:                                             ; preds = %bb10, %bb9
-; CHECK: bb11:
-; CHECK: phi
-; CHECK-NOT: phi
   br label %bb12
 
 bb12:                                             ; preds = %bb11, %bb6
-; CHECK: bb12:
-; CHECK: phi
-; CHECK-NOT: phi
   br i1 undef, label %bb8, label %bb13
 
 bb13:                                             ; preds = %bb12
-; CHECK: bb13:
   ret i8* undef
 }