[PATCH] D40146: [JumpThreading] Preservation of DT and LVI across the pass

[Brian Rzycki via Phabricator via llvm-commits]

brzycki added a comment.

In https://reviews.llvm.org/D40146#968442, @brzycki wrote:

> The patch was reverted in r321832 by @rnk for the following reason:
>
> > This reverts r321825, it causes crashes in Chromium. Reproducer forthcoming.


This is the reduced llvm IR that triggers the failure:

  %struct.hoge = type { i8 }
  
  define void @widget(%struct.hoge* noalias sret %arg) local_unnamed_addr #0 align 2 personality i8* bitcast (i32 (...)* @quux to i8*) {
  bb:
    %tmp = load i32, i32* undef, align 4
    %tmp1 = icmp eq i32 %tmp, 0
    br i1 %tmp1, label %bb2, label %bb13
  
  bb2:
    %tmp3 = getelementptr inbounds %struct.hoge, %struct.hoge* %arg, i64 0, i32 0
    %tmp4 = load i8, i8* %tmp3, align 1
    %tmp5 = icmp eq i8 %tmp4, 0
    br i1 %tmp5, label %bb6, label %bb7
  
  bb6:
    store i8 0, i8* %tmp3, align 1
    br label %bb7
  
  bb7:
    %tmp8 = load i8, i8* %tmp3, align 1
    %tmp9 = icmp ne i8 %tmp8, 0
    %tmp10 = select i1 %tmp9, i1 true, i1 false
    br i1 %tmp10, label %bb12, label %bb11
  
  bb11:
    br label %bb12
  
  bb12:
    br i1 %tmp9, label %bb14, label %bb13
  
  bb13:
    unreachable
  
  bb14:
    ret void
  }
  
  declare i32 @quux(...)

And compile with opt -S -jump-threading <foo.ll

I'm debugging it now and will add to ddt-crash.ll when I re-submit with a fix.


Repository:
  rL LLVM

https://reviews.llvm.org/D40146