significant code bloat vs. gcc at -Os

[regehr]

Bugzilla Link	2717
Resolution	WORKSFORME
Resolved on	Jul 20, 2009 16:03
Version	unspecified
OS	Linux
Attachments	code for this PR
CC	@efriedma-quic

Extended Description

Seen using r55218 on Ubuntu Hardy on ia32.

Here's an example where llvm should probably be producing smaller code. Its
output is 700% larger than gcc's.

regehr@john-home:/volatile/tmp11$ llvm-gcc -Os -w small.c -o small ; size
small
text data bss dec hex filename
6324 252 8 6584 19b8 small
regehr@john-home:/volatile/tmp11$ current-gcc -Os -w small.c -o small ; size
small
text data bss dec hex filename
784 252 12 1048 418 small

Looks easy to fix: at -Os the inliner should not be so aggressive.

[efriedma-quic]

Version without undefined behavior
Not that this really affects the bug as reported, but the original version has undefined behavior due to using an undefined variable and an illegal shift, and therefore could be legitimately optimized to almost anything. Attached version has a real CRC function.

[llvmbot]

Eli, has your inliner changes fixed this?

[efriedma-quic]

I don't think it was my changes, but it appears to work now.