[Instruction] Remove setProfWeight()

[yrouban]

Summary

Remove the function Instruction::setProfWeight() and make use of Instruction::copyMetadata(.., {LLVMContext::MD_prof}).
This is correct for all use cases of setProfWeight() as it is applied to CallBase instructions only.
This change results in prof metadata copied intact even if the source has "VP". The old pair of calls extractProfTotalWeight() + setProfWeight() resulted in setting branch_weights if the source had "VP" data.
This is a split part of D80618.

[davidxl]

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

35

where does 'branch_weights' profdata go?

[yrouban]

no changes but added wider context for ease of review

[yrouban]

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

35

"VP" is preserved as pointed out in the summary.

[hjyamauchi]

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

4957–4958

This refers to SamplePGO preserving the call count in the metadata (which originates in D31344), but it seems more general as it could also apply to calls under PGO (eg the VP metadata).

[davidxl]

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

35

If the invoke is still there, the branch weights should also be copied over, right?

[yrouban]

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

35

In cast-call-combine-prof.ll there is no branch_weights metadata.
As the instcombine is fixed it is not converting "VP" to "branch_weights".
If the invoke instruction had "branch_weights" then the fixed instcombine would preserve it as well. In other words, with this patch we just copy whatever !prof data we have.
!prof can have either "VP" or "branch_weights", but not both.

[davidxl]

lgtm (after fixing the comment mentioned by Hiroshi)

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

35

ah thanks. The old diff does not have context so I read it wrong

llvm/include/llvm/IR/Instruction.h

public:
   /// Returns false if no metadata or invalid metadata was found.
   bool extractProfMetadata(uint64_t &TrueVal, uint64_t &FalseVal) const;
 
   /// Retrieve total raw weight values of a branch.
   /// Returns true on success with profile total weights filled in.
   /// Returns false if no metadata was found.
   bool extractProfTotalWeight(uint64_t &TotalVal) const;
 
-  /// Sets the branch_weights metadata to \p W for CallInst.
-  void setProfWeight(uint64_t W);
-
   /// Set the debug location information for this instruction.
   void setDebugLoc(DebugLoc Loc) { DbgLoc = std::move(Loc); }
 
   /// Return the debug location for this node as a DebugLoc.
   const DebugLoc &getDebugLoc() const { return DbgLoc; }
 
   /// Set or clear the nuw flag on this instruction, which must be an operator
   /// which supports this flag. See LangRef.html for the meaning of this flag.

llvm/lib/IR/Instruction.cpp

 #include "llvm/IR/Instruction.def"
 #undef HANDLE_INST
   }
 
   New->SubclassOptionalData = SubclassOptionalData;
   New->copyMetadata(*this);
   return New;
 }
-
-void Instruction::setProfWeight(uint64_t W) {
-  assert(isa<CallBase>(this) &&
-         "Can only set weights for call like instructions");
-  SmallVector<uint32_t, 1> Weights;
-  Weights.push_back(W);
-  MDBuilder MDB(getContext());
-  setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
-}

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

if (InvokeInst *II = dyn_cast<InvokeInst>(&CB)) {
       auto *NewCall = CallInst::Create(NF, Args, OpBundles, "", &CB);
       NewCall->setTailCallKind(cast<CallInst>(&CB)->getTailCallKind());
       NewCS = NewCall;
     }
     NewCS->setCallingConv(CB.getCallingConv());
     NewCS->setAttributes(
         AttributeList::get(F->getContext(), CallPAL.getFnAttributes(),
                            CallPAL.getRetAttributes(), ArgAttrVec));
-    NewCS->setDebugLoc(CB.getDebugLoc());
-    uint64_t W;
-    if (CB.extractProfTotalWeight(W))
-      NewCS->setProfWeight(W);
+    NewCS->copyMetadata(CB, {LLVMContext::MD_prof, LLVMContext::MD_dbg});
     Args.clear();
     ArgAttrVec.clear();
 
     // Update the callgraph to know that the callsite has been transformed.
     if (ReplaceCallSite)
       (*ReplaceCallSite)(CB, *NewCS);
 
     if (!CB.use_empty()) {

llvm/lib/Transforms/IPO/Attributor.cpp

auto CallSiteReplacementCreator = [&](AbstractCallSite ACS) {
       } else {
         auto *NewCI = CallInst::Create(NewFn, NewArgOperands, OperandBundleDefs,
                                        "", OldCB);
         NewCI->setTailCallKind(cast<CallInst>(OldCB)->getTailCallKind());
         NewCB = NewCI;
       }
 
       // Copy over various properties and the new attributes.
-      uint64_t W;
-      if (OldCB->extractProfTotalWeight(W))
-        NewCB->setProfWeight(W);
+      NewCB->copyMetadata(*OldCB, {LLVMContext::MD_prof, LLVMContext::MD_dbg});
       NewCB->setCallingConv(OldCB->getCallingConv());
-      NewCB->setDebugLoc(OldCB->getDebugLoc());
       NewCB->takeName(OldCB);
       NewCB->setAttributes(AttributeList::get(
           Ctx, OldCallAttributeList.getFnAttributes(),
           OldCallAttributeList.getRetAttributes(), NewArgOperandAttributes));
 
       CallSitePairs.push_back({OldCB, NewCB});
       return true;
     };

llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp

if (InvokeInst *II = dyn_cast<InvokeInst>(CB)) {
                                  Args, OpBundles, "", CB);
     } else {
       NewCB = CallInst::Create(NF, Args, OpBundles, "", CB);
       cast<CallInst>(NewCB)->setTailCallKind(
           cast<CallInst>(CB)->getTailCallKind());
     }
     NewCB->setCallingConv(CB->getCallingConv());
     NewCB->setAttributes(PAL);
-    NewCB->setDebugLoc(CB->getDebugLoc());
-    uint64_t W;
-    if (CB->extractProfTotalWeight(W))
-      NewCB->setProfWeight(W);
+    NewCB->copyMetadata(*CB, {LLVMContext::MD_prof, LLVMContext::MD_dbg});
 
     Args.clear();
 
     if (!CB->use_empty())
       CB->replaceAllUsesWith(NewCB);
 
     NewCB->takeName(CB);
 
if (InvokeInst *II = dyn_cast<InvokeInst>(&CB)) {
                                  Args, OpBundles, "", CB.getParent());
     } else {
       NewCB = CallInst::Create(NFTy, NF, Args, OpBundles, "", &CB);
       cast<CallInst>(NewCB)->setTailCallKind(
           cast<CallInst>(&CB)->getTailCallKind());
     }
     NewCB->setCallingConv(CB.getCallingConv());
     NewCB->setAttributes(NewCallPAL);
-    NewCB->setDebugLoc(CB.getDebugLoc());
-    uint64_t W;
-    if (CB.extractProfTotalWeight(W))
-      NewCB->setProfWeight(W);
+    NewCB->copyMetadata(CB, {LLVMContext::MD_prof, LLVMContext::MD_dbg});
     Args.clear();
     ArgAttrVec.clear();
 
     if (!CB.use_empty() || CB.isUsedByMetadata()) {
       if (NewCB->getType() == CB.getType()) {
         // Return type not changed? Just replace users then.
         CB.replaceAllUsesWith(NewCB);
         NewCB->takeName(&CB);

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

bool InstCombiner::transformConstExprCastCall(CallBase &Call) {
   } else {
     NewCall = Builder.CreateCall(Callee, Args, OpBundles);
     cast<CallInst>(NewCall)->setTailCallKind(
         cast<CallInst>(Caller)->getTailCallKind());
   }
   NewCall->takeName(Caller);
   NewCall->setCallingConv(Call.getCallingConv());
   NewCall->setAttributes(NewCallerPAL);
 
-  // Preserve the weight metadata for the new call instruction. The metadata
-  // is used by SamplePGO to check callsite's hotness.
-  uint64_t W;
-  if (Caller->extractProfTotalWeight(W))
-    NewCall->setProfWeight(W);
+  // Preserve prof metadata if any.
+  NewCall->copyMetadata(*Caller, {LLVMContext::MD_prof});
 
   // Insert a cast of the return type as necessary.
   Instruction *NC = NewCall;
   Value *NV = NC;
   if (OldRetTy != NV->getType() && !Caller->use_empty()) {
     if (!NV->getType()->isVoidTy()) {
       NV = NC = CastInst::CreateBitOrPointerCast(NC, OldRetTy);
       NC->setDebugLoc(Caller->getDebugLoc());

llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

 lpad:
   %lp = landingpad { i8*, i32 }
           filter [0 x i8*] zeroinitializer
   %ehptr = extractvalue { i8*, i32 } %lp, 0
   tail call void @__cxa_call_unexpected(i8* %ehptr) noreturn nounwind
   unreachable
 }
 
-; CHECK: ![[$PROF]] = !{!"branch_weights", i32 2000}
+; CHECK: ![[$PROF]] = !{!"VP", i32 0, i64 2000, i64 -3913987384944532146, i64 2000}
 !0 = !{!"VP", i32 0, i64 2000, i64 -3913987384944532146, i64 2000}
 
 !llvm.module.flags = !{!1}
 
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
 !3 = !{!"ProfileFormat", !"InstrProf"}
 !4 = !{!"TotalCount", i64 10000}