https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121722
Bug ID: 121722
Summary: wrong code generated with -O1 for a program using
_BitInt()
Product: gcc
Version: unknown
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kdudka at redhat dot com
Target Milestone: ---
Created attachment 62235
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=62235&action=edit
reproducer
The attached program (originally provided by Petr Peringer) misbehaves when
compiled with -O1 or higher:
using 129 bit numbers
fib(10) = 2 (should be 55)
I am able to reproduce it with gcc trunk.
Appending -fno-tree-coalesce-vars on the compiler command line makes the
problem go away.
The following bugs seem related:
bug #113372 - wrong code with _BitInt() arithmetics at -O1
bug #119808 - wrong code with _BitInt() and -ftree-coalesce-vars
-fstack-protector-strong
bug #119728 - wrong code with _BitInt() and -O2 -floop-nest-optimize
-fno-tree-dominator-opts -fno-tree-loop-distribute-patterns
-fno-tree-scev-cprop
