[PATCH] D46399: Skip blocks with no predecessors for CFIInstrInserter verify

[Petar Jovanovic via Phabricator via llvm-commits]

petarj added a comment.

In https://reviews.llvm.org/D46399#1086801, @craig.topper wrote:

> This fix fixes the original case, but its easy to break it again
>
>   target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
>   target triple = "x86_64-unknown-linux-gnu"
>  
>   ; Function Attrs: noinline nounwind optnone uwtable
>   define hidden void @foo() #0 {
>   bb:
>     br label %bb1
>  
>   bb1:                                              ; preds = %bb3, %bb
>     %tmp = icmp ne i32 0, 0
>     br i1 %tmp, label %bb2, label %bb3
>  
>   bb2:                                              ; preds = %bb1
>     br label %bb4
>  
>   bb4:                                              ; preds = %bb2
>     br label %bb3
>  
>   bb3:                                              ; preds = %bb4, %bb1
>     br label %bb1
>   }
>  
>   attributes #0 = { noinline nounwind optnone uwtable "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" }
>


Does this example come from a real test case? The issue here is that bb2 will not have predecessors after X86 DAG->DAG Instruction Selection, and this way we reach bb4 from either:

bb0->bb1->bb4 or
bb2->bb3->bb4.

What should be a correct offset for bb4 in this case?


Repository:
  rL LLVM

https://reviews.llvm.org/D46399