1 files changed, 41 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Coroutines/CoroElide.cpp b/llvm/lib/Transforms/Coroutines/CoroElide.cpp
index f032c568449b..d78ab1c1ea28 100644
--- a/llvm/lib/Transforms/Coroutines/CoroElide.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroElide.cpp
@@ -12,6 +12,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -46,7 +47,8 @@ struct Lowerer : coro::LowererBase {
                             AAResults &AA);
   bool shouldElide(Function *F, DominatorTree &DT) const;
   void collectPostSplitCoroIds(Function *F);
-  bool processCoroId(CoroIdInst *, AAResults &AA, DominatorTree &DT);
+  bool processCoroId(CoroIdInst *, AAResults &AA, DominatorTree &DT,
+                     OptimizationRemarkEmitter &ORE);
   bool hasEscapePath(const CoroBeginInst *,
                      const SmallPtrSetImpl<BasicBlock *> &) const;
 };
@@ -299,7 +301,7 @@ void Lowerer::collectPostSplitCoroIds(Function *F) {
 }
 
 bool Lowerer::processCoroId(CoroIdInst *CoroId, AAResults &AA,
-                            DominatorTree &DT) {
+                            DominatorTree &DT, OptimizationRemarkEmitter &ORE) {
   CoroBegins.clear();
   CoroAllocs.clear();
   ResumeAddr.clear();
@@ -343,6 +345,24 @@ bool Lowerer::processCoroId(CoroIdInst *CoroId, AAResults &AA,
   replaceWithConstant(ResumeAddrConstant, ResumeAddr);
 
   bool ShouldElide = shouldElide(CoroId->getFunction(), DT);
+  if (!ShouldElide)
+    ORE.emit([&]() {
+      if (auto FrameSizeAndAlign =
+              getFrameLayout(cast<Function>(ResumeAddrConstant)))
+        return OptimizationRemarkMissed(DEBUG_TYPE, "CoroElide", CoroId)
+               << "'" << ore::NV("callee", CoroId->getCoroutine()->getName())
+               << "' not elided in '"
+               << ore::NV("caller", CoroId->getFunction()->getName())
+               << "' (frame_size="
+               << ore::NV("frame_size", FrameSizeAndAlign->first) << ", align="
+               << ore::NV("align", FrameSizeAndAlign->second.value()) << ")";
+      else
+        return OptimizationRemarkMissed(DEBUG_TYPE, "CoroElide", CoroId)
+               << "'" << ore::NV("callee", CoroId->getCoroutine()->getName())
+               << "' not elided in '"
+               << ore::NV("caller", CoroId->getFunction()->getName())
+               << "' (frame_size=unknown, align=unknown)";
+    });
 
   auto *DestroyAddrConstant = Resumers->getAggregateElement(
       ShouldElide ? CoroSubFnInst::CleanupIndex : CoroSubFnInst::DestroyIndex);
@@ -363,6 +383,23 @@ bool Lowerer::processCoroId(CoroIdInst *CoroId, AAResults &AA,
             << "Elide " << CoroId->getCoroutine()->getName() << " in "
             << CoroId->getFunction()->getName() << "\n";
 #endif
+      ORE.emit([&]() {
+        return OptimizationRemark(DEBUG_TYPE, "CoroElide", CoroId)
+               << "'" << ore::NV("callee", CoroId->getCoroutine()->getName())
+               << "' elided in '"
+               << ore::NV("caller", CoroId->getFunction()->getName())
+               << "' (frame_size="
+               << ore::NV("frame_size", FrameSizeAndAlign->first) << ", align="
+               << ore::NV("align", FrameSizeAndAlign->second.value()) << ")";
+      });
+    } else {
+      ORE.emit([&]() {
+        return OptimizationRemarkMissed(DEBUG_TYPE, "CoroElide", CoroId)
+               << "'" << ore::NV("callee", CoroId->getCoroutine()->getName())
+               << "' not elided in '"
+               << ore::NV("caller", CoroId->getFunction()->getName())
+               << "' (frame_size=unknown, align=unknown)";
+      });
     }
   }
 
@@ -387,10 +424,11 @@ PreservedAnalyses CoroElidePass::run(Function &F, FunctionAnalysisManager &AM) {
 
   AAResults &AA = AM.getResult<AAManager>(F);
   DominatorTree &DT = AM.getResult<DominatorTreeAnalysis>(F);
+  auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
 
   bool Changed = false;
   for (auto *CII : L.CoroIds)
-    Changed |= L.processCoroId(CII, AA, DT);
+    Changed |= L.processCoroId(CII, AA, DT, ORE);
 
   return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
 }