[Coro] Use poison instead of undef as placeholder [NFC]

Author: nunoplopes

llvm/lib/Transforms/Coroutines/CoroCleanup.cpp

@@ -78,7 +78,7 @@ bool Lowerer::lower(Function &F) {
       case Intrinsic::coro_end:
       case Intrinsic::coro_suspend_retcon:
         if (IsPrivateAndUnprocessed) {
-          II->replaceAllUsesWith(UndefValue::get(II->getType()));
+          II->replaceAllUsesWith(PoisonValue::get(II->getType()));
         } else
           continue;
         break;

llvm/lib/Transforms/Coroutines/CoroSplit.cpp

@@ -375,7 +375,7 @@ static void replaceFallthroughCoroEnd(AnyCoroEndInst *End,
     if (auto *RetStructTy = dyn_cast<StructType>(RetTy)) {
       assert(RetStructTy->getNumElements() == NumReturns &&
              "numbers of returns should match resume function singature");
-      Value *ReturnValue = UndefValue::get(RetStructTy);
+      Value *ReturnValue = PoisonValue::get(RetStructTy);
       unsigned Idx = 0;
       for (Value *RetValEl : CoroResults->return_values())
         ReturnValue = Builder.CreateInsertValue(ReturnValue, RetValEl, Idx++);
@@ -406,7 +406,7 @@ static void replaceFallthroughCoroEnd(AnyCoroEndInst *End,
 
     Value *ReturnValue = ConstantPointerNull::get(ContinuationTy);
     if (RetStructTy) {
-      ReturnValue = Builder.CreateInsertValue(UndefValue::get(RetStructTy),
+      ReturnValue = Builder.CreateInsertValue(PoisonValue::get(RetStructTy),
                                               ReturnValue, 0);
     }
     Builder.CreateRet(ReturnValue);
@@ -1304,7 +1304,7 @@ static void handleNoSuspendCoroutine(coro::Shape &Shape) {
   case coro::ABI::Async:
   case coro::ABI::Retcon:
   case coro::ABI::RetconOnce:
-    CoroBegin->replaceAllUsesWith(UndefValue::get(CoroBegin->getType()));
+    CoroBegin->replaceAllUsesWith(PoisonValue::get(CoroBegin->getType()));
     break;
   }
 
@@ -1758,7 +1758,7 @@ static void replaceAsyncResumeFunction(CoroSuspendAsyncInst *Suspend,
   ResumeIntrinsic->replaceAllUsesWith(Val);
   ResumeIntrinsic->eraseFromParent();
   Suspend->setOperand(CoroSuspendAsyncInst::ResumeFunctionArg,
-                      UndefValue::get(Int8PtrTy));
+                      PoisonValue::get(Int8PtrTy));
 }
 
 /// Coerce the arguments in \p FnArgs according to \p FnTy in \p CallArgs.

llvm/lib/Transforms/Coroutines/Coroutines.cpp

@@ -353,18 +353,18 @@ void coro::Shape::invalidateCoroutine(
   assert(!CoroBegin);
   {
     // Replace coro.frame which are supposed to be lowered to the result of
-    // coro.begin with undef.
-    auto *Undef = UndefValue::get(PointerType::get(F.getContext(), 0));
+    // coro.begin with poison.
+    auto *Poison = PoisonValue::get(PointerType::get(F.getContext(), 0));
     for (CoroFrameInst *CF : CoroFrames) {
-      CF->replaceAllUsesWith(Undef);
+      CF->replaceAllUsesWith(Poison);
       CF->eraseFromParent();
     }
     CoroFrames.clear();
 
-    // Replace all coro.suspend with undef and remove related coro.saves if
+    // Replace all coro.suspend with poison and remove related coro.saves if
     // present.
     for (AnyCoroSuspendInst *CS : CoroSuspends) {
-      CS->replaceAllUsesWith(UndefValue::get(CS->getType()));
+      CS->replaceAllUsesWith(PoisonValue::get(CS->getType()));
       CS->eraseFromParent();
       if (auto *CoroSave = CS->getCoroSave())
         CoroSave->eraseFromParent();

llvm/test/Transforms/Coroutines/coro-retcon-once-value.ll

@@ -184,7 +184,7 @@ declare void @print(i32)
 ; CHECK-NEXT:    [[VAL_RELOAD:%.*]] = load i32, ptr [[VAL_RELOAD_ADDR]], align 4
 ; CHECK-NEXT:    [[NEW_VAL:%.*]] = add i32 [[VAL_RELOAD]], 123
 ; CHECK-NEXT:    tail call void @deallocate(ptr [[TMP2]])
-; CHECK-NEXT:    [[TMP3:%.*]] = insertvalue { ptr, i32, ptr } { ptr null, i32 undef, ptr undef }, i32 [[NEW_VAL]], 1
+; CHECK-NEXT:    [[TMP3:%.*]] = insertvalue { ptr, i32, ptr } { ptr null, i32 poison, ptr poison }, i32 [[NEW_VAL]], 1
 ; CHECK-NEXT:    [[TMP4:%.*]] = insertvalue { ptr, i32, ptr } [[TMP3]], ptr @deallocate, 2
 ; CHECK-NEXT:    ret { ptr, i32, ptr } [[TMP4]]
 ;
@@ -202,7 +202,7 @@ declare void @print(i32)
 ; CHECK-NEXT:    [[VAL_RELOAD:%.*]] = load i32, ptr [[VAL_RELOAD_ADDR]], align 4
 ; CHECK-NEXT:    [[NEW_VAL:%.*]] = add i32 [[VAL_RELOAD]], 123
 ; CHECK-NEXT:    tail call void @deallocate(ptr [[TMP2]])
-; CHECK-NEXT:    [[TMP3:%.*]] = insertvalue { ptr, i32, ptr } { ptr null, i32 undef, ptr undef }, i32 [[NEW_VAL]], 1
+; CHECK-NEXT:    [[TMP3:%.*]] = insertvalue { ptr, i32, ptr } { ptr null, i32 poison, ptr poison }, i32 [[NEW_VAL]], 1
 ; CHECK-NEXT:    [[TMP4:%.*]] = insertvalue { ptr, i32, ptr } [[TMP3]], ptr @deallocate, 2
 ; CHECK-NEXT:    ret { ptr, i32, ptr } [[TMP4]]
 ;