https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67781
Bug ID: 67781
Summary: Wrong code generated on mips32 with -O1
-fexpensive-optimizations
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jdboyer at media5corp dot com
Target Milestone: ---
Created attachment 36422
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36422&action=edit
Test program that shows the problem
I'm using a custom build of gcc 5.2.0, for cross-compiling on mips32. It was
generated on a Centos 7 x86_64 system (gcc 4.8.2).
The configuration was done using the following arguments:
--target=mips-linux --enable-tls --with-arch=mips32 --with-float=soft
Then, if I use the generated compiler to compile the attached program
"shift.c", the result will be wrong when using -O2, but good when using -O1.
More precisely, the argument -fexpensive-optimizations is most probably the
cause. Let's say I compile the program like this:
mips-linux-gcc shift.c -o shift -O1 -fexpensive-optimizations
If I execute the program in the embedded system, the result is wrong:
[root@10.11.254.210 jdboyer]# ./shift
123456
If I compile it like this instead:
mips-linux-gcc shift.c -o shift -O2 -fno-expensive-optimizations
The result is good:
[root@10.11.254.210 jdboyer]# ./shift
12345678
