[PATCH] D137866: [Coroutines] Do not add allocas for retcon coroutines

[Sebastian Neubauer via Phabricator via llvm-commits]

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Same as for async-style lowering, if there are no resume points in a
function, the coroutine frame pointer will be replaced by an undef,
making all accesses to the frame undefinde behavior.

Fix this by not adding allocas to the coroutine frame if there are no
resume points.

The test is new, I'll pre-commit if this is accepted.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137866

Files:
  llvm/lib/Transforms/Coroutines/CoroFrame.cpp
  llvm/test/Transforms/Coroutines/coro-retcon.ll


Index: llvm/test/Transforms/Coroutines/coro-retcon.ll
===================================================================
--- llvm/test/Transforms/Coroutines/coro-retcon.ll
+++ llvm/test/Transforms/Coroutines/coro-retcon.ll
@@ -130,12 +130,17 @@
 define i8* @nosuspend(i8* %buffer, i32 %n) {
 ; CHECK-LABEL: @nosuspend(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    unreachable
+; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
+; CHECK-NEXT:    store i32 [[N:%.*]], i32* [[A]], align 4
+; CHECK-NEXT:    call void @use_var_ptr(i32* nonnull [[A]])
+; CHECK-NEXT:    [[AL:%.*]] = load i32, i32* [[A]], align 4
+; CHECK-NEXT:    call void @use_var(i32 [[AL]])
+; CHECK-NEXT:    ret i8* null
 ;
 ; CORO-LABEL: @nosuspend(
 ; CORO-NEXT:  entry:
 ; CORO-NEXT:    [[FRAMEPTR:%.*]] = bitcast i8* undef to %nosuspend.Frame*
-; CORO-NEXT:    [[A:%.*]] = getelementptr inbounds [[NOSUSPEND_FRAME:%.*]], %nosuspend.Frame* [[FRAMEPTR]], i32 0, i32 0
+; CORO-NEXT:    [[A:%.*]] = alloca i32, align 4
 ; CORO-NEXT:    store i32 [[N:%.*]], i32* [[A]], align 4
 ; CORO-NEXT:    call void @use_var_ptr(i32* [[A]])
 ; CORO-NEXT:    [[AL:%.*]] = load i32, i32* [[A]], align 4
Index: llvm/lib/Transforms/Coroutines/CoroFrame.cpp
===================================================================
--- llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2732,7 +2732,7 @@
       Shape.ABI != coro::ABI::RetconOnce)
     sinkLifetimeStartMarkers(F, Shape, Checker);
 
-  if (Shape.ABI != coro::ABI::Async || !Shape.CoroSuspends.empty())
+  if (Shape.ABI == coro::ABI::Switch || !Shape.CoroSuspends.empty())
     collectFrameAllocas(F, Shape, Checker, FrameData.Allocas);
   LLVM_DEBUG(dumpAllocas(FrameData.Allocas));
 


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