https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920
Bug ID: 108920
Summary: Condition falsely optimized out
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: agner at agner dot org
Target Milestone: ---
Created attachment 54526
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54526&action=edit
code to reproduce error
The attached file test.cpp gives wrong code when optimized with -O2 or higher.
To reproduce error, do:
g++ -O2 -m64 -S -o t1.s test.cpp
g++ -O2 -m64 -S -DFIX -o t2.s test.cpp
The condition in line 104 in test.cpp is optimized away in t1.s
The workaround on line 73 is preventing this false optimization with -DFIX to
generate correct code in t2.s
See t2.s line 252-255
