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Newsgroups: | comp.os.msdos.djgpp,gnu.gcc.help |
Subject: | GCC 3.03 makes slow code |
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Date: | Wed, 16 Jan 2002 18:53:25 GMT |
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To: | djgpp AT delorie DOT com |
DJ-Gateway: | from newsgroup comp.os.msdos.djgpp |
Reply-To: | djgpp AT delorie DOT com |
I was testing the latest GCC 3.03 (djgpp) and compiled an application using switches -O9 -fomit-frame-pointer -mcpu=pentium -fschedule-insns2 -fexpensive-optimizations the code it generated run 10-20% slower (on Celeron-A CPU) compared to a version compiled with GCC 2.95 (using identical switches). Adding -mcpu=pentiumpro generated a slightly faster code (around 2%) and I added switch -fno-unroll-loops to a few of the code files which already had manually unrolled code which helped the GCC 3.03 a bit. It's still far from the speed of binary made with GCC 2.95. The code consisted mainly integer comparisons and a lot of memory access (like sorting functions). Could somebody help me with the switches? What switches I should add so that GCC 3 would generate faster code for my CPU? If the problem can't be solved with the switches, is there any hope that future 3.x versions would generate significantly faster code? If not, is there a GCC version planned with GCC 3.03 features without the new speed 'optimizations' of GCC 3.03?
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