[PATCH] D18133: allow branch weight metadata on select instructions (PR26636)

[Sanjay Patel via llvm-commits]

spatel updated this revision to Diff 50604.
spatel added a comment.

Patch updated:
Rather than creating a new regression test to verify the metadata, just add metadata to the existing test case for the transform. 
We're going to need several of these updates, so I don't want to add regression test overhead for duplicate checking of every transform where metadata will be added.


http://reviews.llvm.org/D18133

Files:
  include/llvm/IR/IRBuilder.h
  lib/Transforms/Utils/SimplifyCFG.cpp
  test/Transforms/SimplifyCFG/PhiEliminate2.ll

Index: test/Transforms/SimplifyCFG/PhiEliminate2.ll
===================================================================
--- test/Transforms/SimplifyCFG/PhiEliminate2.ll
+++ test/Transforms/SimplifyCFG/PhiEliminate2.ll
@@ -1,8 +1,11 @@
 ; RUN: opt < %s -simplifycfg -S | FileCheck %s
 
+; Use a select to make this a single BB.
+; Also, make sure the profile metadata is propagated to the select (PR26636).
+
 define i32 @FoldTwoEntryPHINode(i1 %C, i32 %V1, i32 %V2, i16 %V3) {
 entry:
-        br i1 %C, label %then, label %else
+        br i1 %C, label %then, label %else, !prof !0
 then:
         %V4 = or i32 %V2, %V1
         br label %Cont
@@ -18,8 +21,12 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:  %V5 = sext i16 %V3 to i32
 ; CHECK-NEXT:  %V4 = or i32 %V2, %V1
-; CHECK-NEXT:  %V6 = select i1 %C, i32 %V4, i32 %V5
+; CHECK-NEXT:  %V6 = select i1 %C, i32 %V4, i32 %V5, !prof !0
 ; CHECK-NEXT:  %0 = call i32 @FoldTwoEntryPHINode(i1 false, i32 0, i32 0, i16 0)
 ; CHECK-NEXT:  ret i32 %V1
 }
 
+!0 = !{!"branch_weights", i32 3, i32 5}
+
+; CHECK: !0 = !{!"branch_weights", i32 3, i32 5}
+
Index: lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyCFG.cpp
+++ lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1935,7 +1935,8 @@
     Value *TrueVal  = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
     Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
 
-    Value *Select = Builder.CreateSelect(IfCond, TrueVal, FalseVal);
+    MDNode *MDN = InsertPt->getMetadata(LLVMContext::MD_prof);
+    Value *Select = Builder.CreateSelect(IfCond, TrueVal, FalseVal, "", MDN);
     PN->replaceAllUsesWith(Select);
     Select->takeName(PN);
     PN->eraseFromParent();
Index: include/llvm/IR/IRBuilder.h
===================================================================
--- include/llvm/IR/IRBuilder.h
+++ include/llvm/IR/IRBuilder.h
@@ -1569,12 +1569,16 @@
   }
 
   Value *CreateSelect(Value *C, Value *True, Value *False,
-                      const Twine &Name = "") {
+                      const Twine &Name = "", MDNode *ProfWeights = nullptr) {
     if (Constant *CC = dyn_cast<Constant>(C))
       if (Constant *TC = dyn_cast<Constant>(True))
         if (Constant *FC = dyn_cast<Constant>(False))
           return Insert(Folder.CreateSelect(CC, TC, FC), Name);
-    return Insert(SelectInst::Create(C, True, False), Name);
+
+    SelectInst *Sel = SelectInst::Create(C, True, False);
+    // TODO: "unpredictable" metadata can apply to a select too.
+    Sel->setMetadata(LLVMContext::MD_prof, ProfWeights);
+    return Insert(Sel, Name);
   }
 
   VAArgInst *CreateVAArg(Value *List, Type *Ty, const Twine &Name = "") {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D18133.50604.patch
Type: text/x-patch
Size: 2743 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160314/43607b93/attachment.bin>