Merge pull request #2994 from adrian-prantl/77181156

CoroSplit: Replace ad-hoc implementation of reachability with API from CFG.h

Author: adrian-prantl

llvm/lib/Transforms/Coroutines/CoroSplit.cpp

@@ -26,6 +26,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/CallGraphSCCPass.h"
 #include "llvm/Analysis/LazyCallGraph.h"
@@ -37,6 +38,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
@@ -659,8 +661,10 @@ static void salvageCoroDebugInfo(llvm::Function &NewF) {
 
   // Remove all salvaged dbg.declare intrinsics that became
   // either unreachable or stale due to the CoroSplit transformation.
+  DominatorTree DomTree(NewF);
+  SmallDenseMap<BasicBlock *, bool, 8> UnreachableCache;
   auto IsUnreachableBlock = [&](BasicBlock *BB) {
-    return BB->hasNPredecessors(0) && BB != &NewF.getEntryBlock();
+    return !isPotentiallyReachable(&NewF.getEntryBlock(), BB, &DomTree);
   };
   for (DbgDeclareInst *DDI : Worklist) {
     if (IsUnreachableBlock(DDI->getParent()))

llvm/test/Transforms/Coroutines/coro-debug.ll

@@ -20,6 +20,7 @@ entry:
   store i8* %2, i8** %coro_hdl, align 8, !dbg !16
   %3 = call i8 @llvm.coro.suspend(token none, i1 false), !dbg !17
   %conv = sext i8 %3 to i32, !dbg !17
+  %late_local = alloca i32, align 4
   call void @coro.devirt.trigger(i8* null)
   switch i32 %conv, label %sw.default [
     i32 0, label %sw.bb
@@ -57,6 +58,7 @@ coro_Cleanup:                                     ; preds = %sw.epilog, %sw.bb1
 coro_Suspend:                                     ; preds = %coro_Cleanup, %sw.default
   %7 = call i1 @llvm.coro.end(i8* null, i1 false) #7, !dbg !24
   %8 = load i8*, i8** %coro_hdl, align 8, !dbg !24
+  store i32 0, i32* %late_local, !dbg !24
   ret i8* %8, !dbg !24
 }
 
@@ -147,6 +149,8 @@ attributes #7 = { noduplicate }
 ; CHECK: store %f.Frame* {{.*}}, %f.Frame** %[[DBG_PTR]]
 ; CHECK-NOT: alloca %struct.test*
 ; CHECK: call void @llvm.dbg.declare(metadata i32 0, metadata ![[RESUME_CONST:[0-9]+]], metadata !DIExpression())
+; Note that keeping the undef value here could be acceptable, too.
+; CHECK-NOT: call void @llvm.dbg.declare(metadata i32* undef, metadata !{{[0-9]+}}, metadata !DIExpression())
 ; CHECK: call void @coro.devirt.trigger(i8* null)
 ; CHECK: define internal fastcc void @f.destroy(%f.Frame* noalias nonnull align 8 dereferenceable(32) %FramePtr) #0 !dbg ![[DESTROY:[0-9]+]]
 ; CHECK: define internal fastcc void @f.cleanup(%f.Frame* noalias nonnull align 8 dereferenceable(32) %FramePtr) #0 !dbg ![[CLEANUP:[0-9]+]]