SimplifyCFG: Add Trunc, ZExt and SExt to the list of cheap instructions for phi node folding

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130526 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 12 insertions, 6 deletions

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 5177d33959..1bddecb8c4 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -261,6 +261,9 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
   case Instruction::LShr:
   case Instruction::AShr:
   case Instruction::ICmp:
+  case Instruction::Trunc:
+  case Instruction::ZExt:
+  case Instruction::SExt:
     break;   // These are all cheap and non-trapping instructions.
   }
 
diff --git a/test/Transforms/SimplifyCFG/PhiEliminate2.ll b/test/Transforms/SimplifyCFG/PhiEliminate2.ll
index c0f6781293..0b3893d520 100644
--- a/test/Transforms/SimplifyCFG/PhiEliminate2.ll
+++ b/test/Transforms/SimplifyCFG/PhiEliminate2.ll
@@ -1,14 +1,17 @@
 ; RUN: opt < %s -simplifycfg -S | not grep br
 
-define i32 @test(i1 %C, i32 %V1, i32 %V2) {
+define i32 @test(i1 %C, i32 %V1, i32 %V2, i16 %V3) {
 entry:
-        br i1 %C, label %then, label %Cont
+        br i1 %C, label %then, label %else
 then:           ; preds = %entry
-        %V3 = or i32 %V2, %V1           ; <i32> [#uses=1]
+        %V4 = or i32 %V2, %V1           ; <i32> [#uses=1]
         br label %Cont
-Cont:           ; preds = %then, %entry
-        %V4 = phi i32 [ %V1, %entry ], [ %V3, %then ]           ; <i32> [#uses=0]
-        call i32 @test( i1 false, i32 0, i32 0 )                ; <i32>:0 [#uses=0]
+else:           ; preds = %entry
+        %V5 = sext i16 %V3 to i32       ; <i32> [#uses=1]
+        br label %Cont
+Cont:           ; preds = %then, %else
+        %V6 = phi i32 [ %V5, %else ], [ %V4, %then ]            ; <i32> [#uses=0]
+        call i32 @test( i1 false, i32 0, i32 0, i16 0 )         ; <i32>:0 [#uses=0]
         ret i32 %V1
 }