Broken module: CleanupPadInst not the first non-PHI instruction in the block

[Quuxplusone]

Bugzilla Link	PR25326
Status	RESOLVED FIXED
Importance	P normal
Reported by	Alex Crichton (alex@crichton.co)
Reported on	2015-10-26 18:58:09 -0700
Last modified on	2015-10-27 02:37:31 -0700
Version	trunk
Hardware	PC All
CC	david.majnemer@gmail.com, llvm-bugs@lists.llvm.org
Fixed by commit(s)
Attachments	bugpoint-reduced-function.ll.gz (320899 bytes, application/x-gzip)
Blocks
Blocked by
See also

Created attachment 15166 failing IR

When running llc over the LLVM IR attached, it will emit:

CleanupPadInst not the first non-PHI instruction in the block. %cleanuppadi4.i.i.i = cleanuppad [] The unwind destination does not have an exception handling instruction! invoke fastcc void @"ZN3vec13$LT$impl$GT$7reserve7reserve20h8370453893456365494E"(%"3.collections::vec::Vec"* noalias nonnull dereferenceable(12) %vectori4.i.i, i32 %227) to label %normal-return5.i.normal-return10.i_crit_edgei4.i.i unwind label %unwind_custom_i4.i.i.i, !noalias !208 LLVM ERROR: Broken function found, compilation aborted!

When checking the IR, however, it looks like the cleanuppad instruction is the first non-phi instruction in the block?

unwind_custom_i4.i.i.i:
%.lcssa178 = phi %"..." [ %175, %normal-return5i4.i.i.i ] %.pre.i.i.i.2672.i313i4.i.i.lcssa176 = phi %"..." [ %.pre.i.i.i.2672.i313i4.i.i, %normal-return5i4.i.i.i ] %cleanuppadi4.i.i.i = cleanuppad []
br label %loop_body.i.i.i.28i4.i.i.i

I wasn't really quite sure what was going wrong here, and it may be some invalid IR elsewhere in the file (sorry, I couldn't get bugpoint to reduce it further), but perhaps there's something odd going on?

[Quuxplusone]

Attached bugpoint-reduced-function.ll.gz (320899 bytes, application/x-gzip): failing IR

[Quuxplusone]

Aha, it looks like this is actually the -loop-reduce pass going awry, this
command will cause an inttoptr instruction to get inserted before the cleanuppad

    opt -S ./bugpoint-reduced-function.ll -loop-reduce -verify

[Quuxplusone]

reduced IR:
target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
target triple = "i686-pc-windows-msvc"

declare i32 @_except_handler3(...) unnamed_addr

declare void @reserve()

define void @f() unnamed_addr personality i32 (...)* @_except_handler3 {
entry-block:
  br label %start

start:                                            ; preds = %throw, %start,
%entry-block
  %phi1 = phi i8* [ undef, %entry-block ], [ %tmp96, %start ], [ %tmp96, %throw ]
  %tmp96 = getelementptr inbounds i8, i8* %phi1, i32 1
  br i1 undef, label %throw, label %start

pad:                                              ; preds = %throw
  %phi2 = phi i8* [ %tmp96, %throw ]
  %cleanuppadi4.i.i.i = cleanuppad []
  br label %loop_body

loop_body:                                        ; preds = %iter, %pad
  %tmp99 = phi i8* [ %tmp101, %iter ], [ %phi2, %pad ]
  %tmp100 = icmp eq i8* %tmp99, undef
  br i1 %tmp100, label %unwind_out, label %iter

iter:                                             ; preds = %loop_body
  %tmp101 = getelementptr inbounds i8, i8* %tmp99, i32 1
  br i1 undef, label %unwind_out, label %loop_body

unwind_out:                                       ; preds = %iter, %loop_body
  cleanupret %cleanuppadi4.i.i.i unwind to caller

throw:                                            ; preds = %start
  invoke void @reserve()
          to label %start unwind label %pad
}

[Quuxplusone]

The following patch fixes it:
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp
b/lib/Analysis/ScalarEvolutionExpander.cpp
index 86c2f50..e658131 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -148,7 +148,7 @@ Value *SCEVExpander::InsertNoopCastOfTo(Value *V, Type *Ty)
{
     IP = II->getNormalDest()->begin();
   if (CatchPadInst *CPI = dyn_cast<CatchPadInst>(I))
     IP = CPI->getNormalDest()->begin();
-  while (isa<PHINode>(IP) || isa<LandingPadInst>(IP))
+  while (isa<PHINode>(IP) || isa<LandingPadInst>(IP) ||
isa<CleanupPadInst>(IP))
     ++IP;
   return ReuseOrCreateCast(I, Ty, Op, IP);
 }

[Quuxplusone]

Oh wow, thanks for the speedy fix! I'll apply locally and see if I run into anything else and let you know!

[Quuxplusone]

Fixed in r251393.