[GVN, OptDiag] Include the value that is forwarded in load elimination

This requires some changes to the opt-diag API.  Hal and I have
discussed this at the Dev Meeting and came up with a streaming delimiter
(setExtraArgs) to solve this.

Arguments after this delimiter are only included in the optimization
records and not in the remarks printed in the compiler output.  (Note,
how in the test the content of the YAML file changes but the remarks on
the compiler output don't.)

This implements the green GVN message with a bug fix at line
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446

The fix is that now we properly include the constant value in the
message: "load of type i32 eliminated in favor of 7"

Differential Revision: https://reviews.llvm.org/D26489

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288047 91177308-0d34-0410-b5e6-96231b3b80d8

Author: anemet

include/llvm/Analysis/OptimizationDiagnosticInfo.h

@@ -223,6 +223,7 @@ class OptimizationRemarkEmitter {
 namespace ore {
 using NV = DiagnosticInfoOptimizationBase::Argument;
 using setIsVerbose = DiagnosticInfoOptimizationBase::setIsVerbose;
+using setExtraArgs = DiagnosticInfoOptimizationBase::setExtraArgs;
 }
 
 /// OptimizationRemarkEmitter legacy analysis pass

include/llvm/IR/DiagnosticInfo.h

@@ -382,6 +382,12 @@ class DiagnosticInfoOptimizationBase : public DiagnosticInfoWithDebugLocBase {
   /// \brief Used to set IsVerbose via the stream interface.
   struct setIsVerbose {};
 
+  /// \brief When an instance of this is inserted into the stream, the arguments
+  /// following will not appear in the remark printed in the compiler output
+  /// (-Rpass) but only in the optimization record file
+  /// (-fsave-optimization-record).
+  struct setExtraArgs {};
+
   /// \brief Used in the streaming interface as the general argument type.  It
   /// internally converts everything into a key-value pair.
   struct Argument {
@@ -452,6 +458,7 @@ class DiagnosticInfoOptimizationBase : public DiagnosticInfoWithDebugLocBase {
   DiagnosticInfoOptimizationBase &operator<<(StringRef S);
   DiagnosticInfoOptimizationBase &operator<<(Argument A);
   DiagnosticInfoOptimizationBase &operator<<(setIsVerbose V);
+  DiagnosticInfoOptimizationBase &operator<<(setExtraArgs EA);
 
   /// \see DiagnosticInfo::print.
   void print(DiagnosticPrinter &DP) const override;
@@ -501,6 +508,11 @@ class DiagnosticInfoOptimizationBase : public DiagnosticInfoWithDebugLocBase {
   /// The remark is expected to be noisy.
   bool IsVerbose = false;
 
+  /// \brief If positive, the index of the first argument that only appear in
+  /// the optimization records and not in the remark printed in the compiler
+  /// output.
+  int FirstExtraArgIndex = -1;
+
   friend struct yaml::MappingTraits<DiagnosticInfoOptimizationBase *>;
 };
 

lib/IR/DiagnosticInfo.cpp

@@ -170,14 +170,25 @@ const std::string DiagnosticInfoWithDebugLocBase::getLocationStr() const {
     getLocation(&Filename, &Line, &Column);
   return (Filename + ":" + Twine(Line) + ":" + Twine(Column)).str();
 }
+
 DiagnosticInfoOptimizationBase::Argument::Argument(StringRef Key, Value *V)
-    : Key(Key), Val(GlobalValue::getRealLinkageName(V->getName())) {
+    : Key(Key) {
   if (auto *F = dyn_cast<Function>(V)) {
     if (DISubprogram *SP = F->getSubprogram())
       DLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
   }
   else if (auto *I = dyn_cast<Instruction>(V))
     DLoc = I->getDebugLoc();
+
+  // Only include names that correspond to user variables.  FIXME: we should use
+  // debug info if available to get the name of the user variable.
+  if (isa<llvm::Argument>(V) || isa<GlobalValue>(V))
+    Val = GlobalValue::getRealLinkageName(V->getName());
+  else if (isa<Constant>(V)) {
+    raw_string_ostream OS(Val);
+    V->printAsOperand(OS, /*PrintType=*/false);
+  } else if (auto *I = dyn_cast<Instruction>(V))
+    Val = I->getOpcodeName();
 }
 
 DiagnosticInfoOptimizationBase::Argument::Argument(StringRef Key, Type *T)
@@ -359,10 +370,19 @@ operator<<(setIsVerbose V) {
   return *this;
 }
 
+DiagnosticInfoOptimizationBase &DiagnosticInfoOptimizationBase::
+operator<<(setExtraArgs EA) {
+  FirstExtraArgIndex = Args.size();
+  return *this;
+}
+
 std::string DiagnosticInfoOptimizationBase::getMsg() const {
   std::string Str;
   raw_string_ostream OS(Str);
-  for (const DiagnosticInfoOptimizationBase::Argument &Arg : Args)
+  for (const DiagnosticInfoOptimizationBase::Argument &Arg :
+       make_range(Args.begin(), FirstExtraArgIndex == -1
+                                    ? Args.end()
+                                    : Args.begin() + FirstExtraArgIndex))
     OS << Arg.Val;
   return OS.str();
 }

lib/Transforms/Scalar/GVN.cpp

@@ -1590,10 +1590,13 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
   return true;
 }
 
-static void reportLoadElim(LoadInst *LI, OptimizationRemarkEmitter *ORE) {
+static void reportLoadElim(LoadInst *LI, Value *AvailableValue,
+                           OptimizationRemarkEmitter *ORE) {
+  using namespace ore;
   ORE->emit(OptimizationRemark(DEBUG_TYPE, "LoadElim", LI)
-            << "load of type " << ore::NV("Type", LI->getType())
-            << " eliminated");
+            << "load of type " << NV("Type", LI->getType()) << " eliminated"
+            << setExtraArgs() << " in favor of "
+            << NV("InfavorOfValue", AvailableValue));
 }
 
 /// Attempt to eliminate a load whose dependencies are
@@ -1666,7 +1669,7 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
       MD->invalidateCachedPointerInfo(V);
     markInstructionForDeletion(LI);
     ++NumGVNLoad;
-    reportLoadElim(LI, ORE);
+    reportLoadElim(LI, V, ORE);
     return true;
   }
 
@@ -1813,7 +1816,7 @@ bool GVN::processLoad(LoadInst *L) {
     patchAndReplaceAllUsesWith(L, AvailableValue);
     markInstructionForDeletion(L);
     ++NumGVNLoad;
-    reportLoadElim(L, ORE);
+    reportLoadElim(L, AvailableValue, ORE);
     // Tell MDA to rexamine the reused pointer since we might have more
     // information after forwarding it.
     if (MD && AvailableValue->getType()->getScalarType()->isPointerTy())

test/Transforms/GVN/opt-remarks.ll

@@ -15,6 +15,8 @@
 ; YAML-NEXT:   - String:          'load of type '
 ; YAML-NEXT:   - Type:            i32
 ; YAML-NEXT:   - String:          ' eliminated'
+; YAML-NEXT:   - String:          ' in favor of '
+; YAML-NEXT:   - InfavorOfValue:  i
 ; YAML-NEXT: ...
 ; YAML-NEXT: --- !Passed
 ; YAML-NEXT: Pass:            gvn
@@ -24,6 +26,8 @@
 ; YAML-NEXT:   - String:          'load of type '
 ; YAML-NEXT:   - Type:            i32
 ; YAML-NEXT:   - String:          ' eliminated'
+; YAML-NEXT:   - String:          ' in favor of '
+; YAML-NEXT:   - InfavorOfValue:  '4'
 ; YAML-NEXT: ...
 ; YAML-NEXT: --- !Passed
 ; YAML-NEXT: Pass:            gvn
@@ -33,6 +37,8 @@
 ; YAML-NEXT:   - String:          'load of type '
 ; YAML-NEXT:   - Type:            i32
 ; YAML-NEXT:   - String:          ' eliminated'
+; YAML-NEXT:   - String:          ' in favor of '
+; YAML-NEXT:   - InfavorOfValue:  load
 ; YAML-NEXT: ...