[PATCH] D155711: [SimplifyCFG] Hoist common instructions on Switch.

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

In D155711#4648971 <https://reviews.llvm.org/D155711#4648971>, @MaskRay wrote:

> In D155711#4648928 <https://reviews.llvm.org/D155711#4648928>, @MaskRay wrote:
>
>> Early heads-up we internally have identified a crash due to this change.
>
> I will try giving a reproduce later, but am reverting this now.
>
>   musttail call must precede a ret with an optional bitcast



  % cat x.ll
  source_filename = "<stdin>"
  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  target triple = "x86_64-unknown-linux-gnu"
  
  define ptr @ham(ptr %arg, ptr %arg1, ptr %arg2, i64 %arg3, ptr %arg4, i64 %arg5) {
  bb:
    %load = load i16, ptr %arg, align 2
    %and = and i16 %load, 1
    %icmp = icmp eq i16 %and, 0
    br i1 %icmp, label %bb7, label %bb6
  
  bb6:                                              ; preds = %bb
    ret ptr null
  
  bb7:                                              ; preds = %bb
    switch i16 %load, label %bb13 [
      i16 0, label %bb8
      i16 1, label %bb9
      i16 2, label %bb11
    ]
  
  bb8:                                              ; preds = %bb7
    %call = musttail call ptr @zot(ptr %arg, ptr %arg1, ptr %arg2, i64 %arg3, ptr %arg4, i64 %arg5)
    ret ptr %call
  
  bb9:                                              ; preds = %bb7
    %call10 = musttail call ptr @zot(ptr %arg, ptr %arg1, ptr %arg2, i64 %arg3, ptr %arg4, i64 %arg5)
    ret ptr %call10
  
  bb11:                                             ; preds = %bb7
    %call12 = musttail call ptr @zot(ptr %arg, ptr %arg1, ptr %arg2, i64 %arg3, ptr %arg4, i64 %arg5)
    ret ptr %call12
  
  bb13:                                             ; preds = %bb7
    unreachable
  }
  
  declare ptr @zot(ptr, ptr, ptr, i64, ptr, i64)
  % opt -O2 -S < x.ll
  musttail call must precede a ret with an optional bitcast
    %call = musttail call ptr @zot(ptr nonnull %arg, ptr %arg1, ptr %arg2, i64 %arg3, ptr %arg4, i64 %arg5)
  LLVM ERROR: Broken module found, compilation aborted!
  PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
  ...


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https://reviews.llvm.org/D155711