[llvm] 032251e - [Coroutines] Fix PR45130

[Richard Smith via llvm-commits]

Can we get this into the 10.0.1 release? This fixes a nasty miscompile for
C++20 coroutines.

On Thu, 19 Mar 2020 at 20:28, Jun Ma via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

>
> Author: Jun Ma
> Date: 2020-03-20T11:27:08+08:00
> New Revision: 032251e34d17c1cbf21e7571514bb775ed5cdf30
>
> URL:
> https://github.com/llvm/llvm-project/commit/032251e34d17c1cbf21e7571514bb775ed5cdf30
> DIFF:
> https://github.com/llvm/llvm-project/commit/032251e34d17c1cbf21e7571514bb775ed5cdf30.diff
>
> LOG: [Coroutines] Fix PR45130
>
> For now, when final suspend can be simplified by simplifySuspendPoint,
> handleFinalSuspend is executed as well to remove last case in switch
> instruction. This patch fixes it.
>
> Differential Revision: https://reviews.llvm.org/D76345
>
> Added:
>
>
> Modified:
>     llvm/lib/Transforms/Coroutines/CoroSplit.cpp
>     llvm/test/Transforms/Coroutines/no-suspend.ll
>
> Removed:
>
>
>
>
> ################################################################################
> diff  --git a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
> b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
> index 04c06e3653d7..8aca27b9b42c 100644
> --- a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
> +++ b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
> @@ -1157,7 +1157,10 @@ static void simplifySuspendPoints(coro::Shape
> &Shape) {
>    if (N == 0)
>      return;
>    while (true) {
> -    if (simplifySuspendPoint(cast<CoroSuspendInst>(S[I]),
> Shape.CoroBegin)) {
> +    auto SI = cast<CoroSuspendInst>(S[I]);
> +    // Leave final.suspend to handleFinalSuspend since it is undefined
> behavior
> +    // to resume a coroutine suspended at the final suspend point.
> +    if (!SI->isFinal() && simplifySuspendPoint(SI, Shape.CoroBegin)) {
>        if (--N == I)
>          break;
>        std::swap(S[I], S[N]);
>
> diff  --git a/llvm/test/Transforms/Coroutines/no-suspend.ll
> b/llvm/test/Transforms/Coroutines/no-suspend.ll
> index be48c2ab09fe..211e16c6ccdb 100644
> --- a/llvm/test/Transforms/Coroutines/no-suspend.ll
> +++ b/llvm/test/Transforms/Coroutines/no-suspend.ll
> @@ -362,6 +362,58 @@ suspend:
>    ret void
>  }
>
> +; SimplifySuspendPoint should not simplify final suspend point
> +;
> +; CHECK-LABEL: define void @cannot_simplify_final_suspend(
> +; CHECK-NEXT:  entry:
> +; CHECK-NEXT:     llvm.coro.id
> +;
> +define void @cannot_simplify_final_suspend() "coroutine.presplit"="1"
> personality i32 0 {
> +entry:
> +  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
> +  %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
> +  br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
> +dyn.alloc:
> +  %size = call i32 @llvm.coro.size.i32()
> +  %alloc = call i8* @malloc(i32 %size)
> +  br label %coro.begin
> +coro.begin:
> +  %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
> +  %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
> +  br label %body
> +body:
> +  %save = call token @llvm.coro.save(i8* %hdl)
> +  %subfn = call i8* @llvm.coro.subfn.addr(i8* %hdl, i8 1)
> +  %bcast = bitcast i8* %subfn to void (i8*)*
> +  invoke fastcc void %bcast(i8* %hdl) to label %real_susp unwind label
> %lpad
> +
> +real_susp:
> +  %0 = call i8 @llvm.coro.suspend(token %save, i1 1)
> +  switch i8 %0, label %suspend [i8 0, label %resume
> +                                i8 1, label %pre.cleanup]
> +resume:
> +  call void @print(i32 0)
> +  br label %cleanup
> +
> +pre.cleanup:
> +  call void @print(i32 1)
> +  br label %cleanup
> +
> +cleanup:
> +  %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
> +  call void @free(i8* %mem)
> +  br label %suspend
> +suspend:
> +  call i1 @llvm.coro.end(i8* %hdl, i1 false)
> +  ret void
> +lpad:
> +  %lpval = landingpad { i8*, i32 }
> +     cleanup
> +
> +  call void @print(i32 2)
> +  resume { i8*, i32 } %lpval
> +}
> +
>  declare i8* @malloc(i32)
>  declare void @free(i8*)
>  declare void @print(i32)
>
>
>
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