[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

4958–4959

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

   /// 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); }
 

llvm/lib/IR/Instruction.cpp

   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

     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();
 

llvm/lib/Transforms/IPO/Attributor.cpp

       }
 
       // 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(),

llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp

     }
     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();
 

     }
     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();
 

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

 
   // 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);
+  NewCall->copyMetadata(*Caller, {LLVMContext::MD_prof});
 
   // Insert a cast of the return type as necessary.
   Instruction *NC = NewCall;

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

   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}