http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55667
Bug #: 55667
Summary: [regression] -O1 enables frame pointer push to move
around on x86_64
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: dfla...@nist.gov
Target: x86_64-intel-linux-gnu
Created attachment 28939
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28939
preprocessed test program
On x86_64 linux, with -fno-omit-frame-pointer and -O1, gcc 4.7.x (verified
for 4.7.0 and 4.7.2) allow the frame pointer (rbp) push instruction to wander
away from the beginning of a function. As a result, profiling tools
including perf and OProfile determine incorrect call chains, and subsequent
calculations of call graphs and total time are wrong.
The problem does not occur if any of the following are true:
-O0 instead of -O1
-m32 instead of -m64
gcc 4.6.3 instead of 4.7.x
The preprocessed source of a small program to demonstrate the problem is
attached. Example output from the profiling tools and various versions of
gcc, as well as the original small program, was sent to the oprofile-list at
2012-12-12 13:45 EST, but the list archive is presently unreachable, so email
me for a copy if needed.
