https://bugs.llvm.org/show_bug.cgi?id=32721
Bug ID: 32721
Summary: IfConversion creating bad CFG when merging triangle
Product: new-bugs
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: mikael.hol...@ericsson.com
CC: llvm-bugs@lists.llvm.org
Created attachment 18319
--> https://bugs.llvm.org/attachment.cgi?id=18319&action=edit
Reproducer
Repriduce with
llc -mtriple thumbv7-apple-ios ifcvt_triangle_false_return.mir
-run-pass=if-converter -o - -debug
This yields
bb.0:
successors: %bb.1(0x80000000)
bb.1:
successors: %bb.2(0x40000000), %bb.1(0x00000000)
BX_RET 14, _, implicit killed %r0
bb.2:
Looking at bb.1, we have a single unconditional return, but bb.1 still has two
successors? This seems wrong to me.
The situation occurs since BX_RET is a return instruction that ARM's
analyzeBranch
implementation returns true for so the IfConversion call to
RemoveExtraEdges(BBI)
won't do anything, and thus leave the CFG is a bad state.
There are some calls to removeSuccessor() here and there in IfConversion.cpp:
// RemoveExtraEdges won't work if the block has an unanalyzable branch, so
// explicitly remove CvtBBI as a successor.
BBI.BB->removeSuccessor(&CvtMBB, true);
but none of them catch this case.
(Originally found when compiling for my out-of-tree backend, so I created a MIR
test case and modified it to expose the problem also on ARM.)
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
