[llvm] r267491 - Add check for "branch_weights" with prof metadata

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Apr 25 18:15:16 2016
New Revision: 267491

URL: http://llvm.org/viewvc/llvm-project?rev=267491&view=rev
Log:
Add check for "branch_weights" with prof metadata

While we're here, fix the comment and variable names to make it
clear that these are raw weights, not percentages.


Modified:
    llvm/trunk/include/llvm/IR/Instructions.h
    llvm/trunk/lib/IR/Instructions.cpp
    llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll

Modified: llvm/trunk/include/llvm/IR/Instructions.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Instructions.h?rev=267491&r1=267490&r2=267491&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Instructions.h (original)
+++ llvm/trunk/include/llvm/IR/Instructions.h Mon Apr 25 18:15:16 2016
@@ -2906,9 +2906,10 @@ public:
   /// continues to map correctly to each operand.
   void swapSuccessors();
 
-  /// Retrieve the probabilities of a conditional branch. Returns true on
-  /// success, or returns false if no or invalid metadata was found.
-  bool extractProfMetadata(uint64_t &ProbTrue, uint64_t &ProbFalse);
+  /// Retrieve the raw weight values of a conditional branch.
+  /// Returns true on success with profile weights filled in.
+  /// Returns false if no metadata or invalid metadata was found.
+  bool extractProfMetadata(uint64_t &TrueVal, uint64_t &FalseVal);
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const Instruction *I) {

Modified: llvm/trunk/lib/IR/Instructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Instructions.cpp?rev=267491&r1=267490&r2=267491&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Instructions.cpp (original)
+++ llvm/trunk/lib/IR/Instructions.cpp Mon Apr 25 18:15:16 2016
@@ -1120,20 +1120,24 @@ void BranchInst::swapSuccessors() {
               MDNode::get(ProfileData->getContext(), Ops));
 }
 
-bool BranchInst::extractProfMetadata(uint64_t &ProbTrue, uint64_t &ProbFalse) {
+bool BranchInst::extractProfMetadata(uint64_t &TrueVal, uint64_t &FalseVal) {
   assert(isConditional() &&
          "Looking for probabilities on unconditional branch?");
   auto *ProfileData = getMetadata(LLVMContext::MD_prof);
   if (!ProfileData || ProfileData->getNumOperands() != 3)
     return false;
 
+  auto *ProfDataName = dyn_cast<MDString>(ProfileData->getOperand(0));
+  if (!ProfDataName || !ProfDataName->getString().equals("branch_weights"))
+    return false;
+
   auto *CITrue = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(1));
   auto *CIFalse = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2));
   if (!CITrue || !CIFalse)
     return false;
 
-  ProbTrue = CITrue->getValue().getZExtValue();
-  ProbFalse = CIFalse->getValue().getZExtValue();
+  TrueVal = CITrue->getValue().getZExtValue();
+  FalseVal = CIFalse->getValue().getZExtValue();
 
   return true;
 }

Modified: llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll?rev=267491&r1=267490&r2=267491&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll Mon Apr 25 18:15:16 2016
@@ -21,6 +21,29 @@ Z:
   ret void
 }
 
+; Make sure the metadata name string is "branch_weights" before propagating it.
+
+define void @fake_weights(i1 %a, i1 %b) {
+; CHECK-LABEL: @fake_weights(
+entry:
+  br i1 %a, label %Y, label %X, !prof !12
+; CHECK:        %or.cond = and i1 %a.not, %c
+; CHECK-NEXT:   br i1 %or.cond, label %Z, label %Y
+; CHECK-NOT:    !prof !0
+; CHECK:      Y:
+X:
+  %c = or i1 %b, false
+  br i1 %c, label %Z, label %Y, !prof !1
+
+Y:
+  call void @helper(i32 0)
+  ret void
+
+Z:
+  call void @helper(i32 1)
+  ret void
+}
+
 define void @test2(i1 %a, i1 %b) {
 ; CHECK-LABEL: @test2(
 entry:
@@ -376,6 +399,7 @@ for.exit:
 !9 = !{!"branch_weights", i32 7, i32 6}
 !10 = !{!"branch_weights", i32 672646, i32 21604207}
 !11 = !{!"branch_weights", i32 6960, i32 21597248}
+!12 = !{!"these_are_not_the_branch_weights_you_are_looking_for", i32 3, i32 5}
 
 ; CHECK: !0 = !{!"branch_weights", i32 5, i32 11}
 ; CHECK: !1 = !{!"branch_weights", i32 1, i32 5}