[Coroutine] Record the elided coroutines

Reviewed By: lxfind

Differential Revision: https://reviews.llvm.org/D105606

llvm/lib/Transforms/Coroutines/CoroElide.cpp

@@ -17,6 +17,7 @@
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FileSystem.h"
 
 using namespace llvm;
 
@@ -24,6 +25,12 @@ using namespace llvm;
 
 STATISTIC(NumOfCoroElided, "The # of coroutine get elided.");
 
+#ifndef NDEBUG
+static cl::opt<std::string> CoroElideInfoOutputFilename(
+    "coro-elide-info-output-file", cl::value_desc("filename"),
+    cl::desc("File to record the coroutines got elided"), cl::Hidden);
+#endif
+
 namespace {
 // Created on demand if the coro-elide pass has work to do.
 struct Lowerer : coro::LowererBase {
@@ -121,6 +128,21 @@ static Instruction *getFirstNonAllocaInTheEntryBlock(Function *F) {
   llvm_unreachable("no terminator in the entry block");
 }
 
+#ifndef NDEBUG
+static std::unique_ptr<raw_fd_ostream> getOrCreateLogFile() {
+  assert(!CoroElideInfoOutputFilename.empty() &&
+         "coro-elide-info-output-file shouldn't be empty");
+  std::error_code EC;
+  auto Result = std::make_unique<raw_fd_ostream>(CoroElideInfoOutputFilename,
+                                                 EC, sys::fs::OF_Append);
+  if (!EC)
+    return Result;
+  llvm::errs() << "Error opening coro-elide-info-output-file '"
+               << CoroElideInfoOutputFilename << " for appending!\n";
+  return std::make_unique<raw_fd_ostream>(2, false); // stderr.
+}
+#endif
+
 // To elide heap allocations we need to suppress code blocks guarded by
 // llvm.coro.alloc and llvm.coro.free instructions.
 void Lowerer::elideHeapAllocations(Function *F, uint64_t FrameSize,
@@ -344,6 +366,12 @@ bool Lowerer::processCoroId(CoroIdInst *CoroId, AAResults &AA,
                          FrameSizeAndAlign.second, AA);
     coro::replaceCoroFree(CoroId, /*Elide=*/true);
     NumOfCoroElided++;
+#ifndef NDEBUG
+    if (!CoroElideInfoOutputFilename.empty())
+      *getOrCreateLogFile()
+          << "Elide " << CoroId->getCoroutine()->getName() << " in "
+          << CoroId->getFunction()->getName() << "\n";
+#endif
   }
 
   return true;

llvm/test/Transforms/Coroutines/coro-elide-stat.ll

@@ -4,8 +4,15 @@
 ; RUN: opt < %s -S \
 ; RUN:   -passes='cgscc(repeat<2>(inline,function(coro-elide,dce)))' -stats 2>&1 \
 ; RUN:   | FileCheck %s
+; RUN: opt < %s --disable-output \
+; RUN:   -passes='cgscc(repeat<2>(inline,function(coro-elide,dce)))' \
+; RUN:   -coro-elide-info-output-file=%t && \
+; RUN:  cat %t \
+; RUN:   | FileCheck %s --check-prefix=FILE
 
 ; CHECK: 2 coro-elide  - The # of coroutine get elided.
+; FILE: Elide f in callResume
+; FILE: Elide f in callResumeMultiRetDommmed
 
 declare void @print(i32) nounwind