[Coroutine] Record the elided coroutines

[ChuanqiXu]

Summary

This is follow up for D105095. In D105095, we recorded how many coroutine got elided.
Then in practice, it is helpful to know the accurate coroutine got elided.

I think it is helpful for others who use a large projects.

Test Plan: check-llvm

[ChuanqiXu]

gentle ping~

[lxfind]

In D105606#2889219, @ChuanqiXu wrote:

gentle ping~

fix lint?

[ChuanqiXu]

In D105606#2903641, @lxfind wrote:

In D105606#2889219, @ChuanqiXu wrote:

gentle ping~

fix lint?

I am not sure if I understand your point correctly. The intent of the diff is going to record the coroutines got elided. There are options to dump informations to specific file like info-output-file in Timer.cpp. So I guess we can do similar things in coroutine.

[lxfind]

In D105606#2903644, @ChuanqiXu wrote:

In D105606#2903641, @lxfind wrote:

In D105606#2889219, @ChuanqiXu wrote:

gentle ping~

fix lint?

I am not sure if I understand your point correctly. The intent of the diff is going to record the coroutines got elided. There are options to dump informations to specific file like info-output-file in Timer.cpp. So I guess we can do similar things in coroutine.

I mean fix the lint warning.

[ChuanqiXu]

Address comments.

[lxfind]

llvm/lib/Transforms/Coroutines/CoroElide.cpp

28

Shouldn't this be under NDEBUG too?

[ChuanqiXu]

Address comments.

llvm/lib/Transforms/Coroutines/CoroElide.cpp

 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FileSystem.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "coro-elide"
 
 STATISTIC(NumOfCoroElided, "The # of coroutine get elided.");
 
+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);
+
 namespace {
 // Created on demand if the coro-elide pass has work to do.
 struct Lowerer : coro::LowererBase {
   SmallVector<CoroIdInst *, 4> CoroIds;
   SmallVector<CoroBeginInst *, 1> CoroBegins;
   SmallVector<CoroAllocInst *, 1> CoroAllocs;
   SmallVector<CoroSubFnInst *, 4> ResumeAddr;
   DenseMap<CoroBeginInst *, SmallVector<CoroSubFnInst *, 4>> DestroyAddr;

 // Finds first non alloca instruction in the entry block of a function.
 static Instruction *getFirstNonAllocaInTheEntryBlock(Function *F) {
   for (Instruction &I : F->getEntryBlock())
     if (!isa<AllocaInst>(&I))
       return &I;
   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,
                                    Align FrameAlign, AAResults &AA) {
   LLVMContext &C = F->getContext();
   auto *InsertPt =
       getFirstNonAllocaInTheEntryBlock(CoroIds.front()->getFunction());
 
for (auto &It : DestroyAddr)
     replaceWithConstant(DestroyAddrConstant, It.second);
 
   if (ShouldElide) {
     auto FrameSizeAndAlign = getFrameLayout(cast<Function>(ResumeAddrConstant));
     elideHeapAllocations(CoroId->getFunction(), FrameSizeAndAlign.first,
                          FrameSizeAndAlign.second, AA);
     coro::replaceCoroFree(CoroId, /*Elide=*/true);
     NumOfCoroElided++;
+#ifndef NDEBUG
+    if (!CoroElideInfoOutputFilename.empty()) {
+      auto outputFile = getOrCreateLogFile();
+      *outputFile << "Elide " << CoroId->getCoroutine()->getName() << " in "
+                  << CoroId->getFunction()->getName() << "\n";
+    }
+#endif
   }
 
   return true;
 }
 
 // See if there are any coro.subfn.addr instructions referring to coro.devirt
 // trigger, if so, replace them with a direct call to devirt trigger function.
 static bool replaceDevirtTrigger(Function &F) {

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

 ; Tests that the number elided coroutine is record correctly.
 ; REQUIRES: asserts
 ;
 ; 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
 
 ; resume part of the coroutine
 define fastcc void @f.resume(i8*) {
   tail call void @print(i32 0)
   ret void
 }