Overly Hyped [LWN.net]

Overly Hyped

Posted Nov 13, 2008 18:40 UTC (Thu) by darthscsi (guest, #8111)
In reply to: Overly Hyped by clugstj
Parent article: Things that go Clang in the night: LLVM 2.4 released (ars technica)

Interprocedural optimization of an entire linux kernel not enough for you (SOSP2007, though actually that was just a side effect of making the kernel memory safe (e.g. no buffer overflows, etc))? JITing of per-application OpenGL stacks (MacOS)? Compiling iPhone Apps? JITing image processing routines optimized for the specific image and combination of transformations (adobe). C to flash translation so you can run C programs (including bash, python, and nintendo enumlators) in a browser (adobe)? These are not real enough workloads for you? Most of those are shipping.

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Overly Hyped

Posted Nov 13, 2008 19:51 UTC (Thu) by clugstj (subscriber, #4020) [Link] (5 responses)

Sorry, I've got to call Bullshit on this. If there were a compiler for the linux kernel that was as wonderful as you say, all the kernel developers would be using it.

Overly Hyped

Posted Nov 13, 2008 23:58 UTC (Thu) by darthscsi (guest, #8111) [Link] (4 responses)

Go ahead and call bullshit. Let me refer you to:
http://portal.acm.org/citation.cfm?id=1294295
for the linux kernel, and other users:
http://www.tungstengraphics.com/wiki/index.php/Gallium3D#...
http://www.osnews.com/story/15530/LLVM-at-Apple-the-OpenG...
http://www.ipodobserver.com/story/30184
http://arstechnica.com/reviews/os/mac-os-x-10-5.ars/11
http://www.ffconsultancy.com/products/ocaml_journal/?llvm
http://ajaxian.com/archives/llvm-and-running-c-as-well-as...

Oh and back to the kernel...

llvm-gcc -Wp,-MD,arch/x86/kernel/.ioport.o.d -nostdinc -isystem ~~/cfe/install/bin/../lib/gcc/i686-pc-linux-gnu/4.2.1/include -D__KERNEL__ -Iinclude -I~~/Applications/linux-2.6.27.5/arch/x86/include -include include/linux/autoconf.h -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -O0 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=pentium2 -mtune=generic -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Iinclude/asm-x86/mach-generic -Iinclude/asm-x86/mach-default -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(ioport)" -D"KBUILD_MODNAME=KBUILD_STR(ioport)" -c -o arch/x86/kernel/ioport.o arch/x86/kernel/ioport.c

llvm-gcc -Wp,-MD,arch/x86/kernel/.ldt.o.d -nostdinc -isystem ~~/cfe/install/bin/../lib/gcc/i686-pc-linux-gnu/4.2.1/include -D__KERNEL__ -Iinclude -I~~/Applications/linux-2.6.27.5/arch/x86/include -include include/linux/autoconf.h -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -O0 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=pentium2 -mtune=generic -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Iinclude/asm-x86/mach-generic -Iinclude/asm-x86/mach-default -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(ldt)" -D"KBUILD_MODNAME=KBUILD_STR(ldt)" -c -o arch/x86/kernel/ldt.o arch/x86/kernel/ldt.c

llvm-gcc -Wp,-MD,arch/x86/kernel/.setup.o.d -nostdinc -isystem ~~/cfe/install/bin/../lib/gcc/i686-pc-linux-gnu/4.2.1/include -D__KERNEL__ -Iinclude -I~~/Applications/linux-2.6.27.5/arch/x86/include -include include/linux/autoconf.h -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -O0 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=pentium2 -mtune=generic -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Iinclude/asm-x86/mach-generic -Iinclude/asm-x86/mach-default -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(setup)" -D"KBUILD_MODNAME=KBUILD_STR(setup)" -c -o arch/x86/kernel/setup.o arch/x86/kernel/setup.c

just to pick out something scrolling by my screen right now (Paths slightly mangled for privacy). (The llvm knowledgeable will recognize that this build is not doing IPO, but see the SOSP07 paper where complex interprocedural analysis and transformations were performed on the entire kernel).

Overly Hyped

Posted Nov 14, 2008 2:41 UTC (Fri) by clugstj (subscriber, #4020) [Link] (2 responses)

Please read the comment to which you are replying. The article is about something called "Clang" that is to replace the GCC-based front end to LLVM. You are apparently not using "Clang" because your command line begins with "llvm-gcc". So what you are hyping is not actually what the article was about.

Overly Hyped

Posted Nov 14, 2008 3:41 UTC (Fri) by darthscsi (guest, #8111) [Link] (1 responses)

Please read the article, the article is about the llvm 2.4 release. Clang is an in development sub-project of that. I am quite aware that I am using llvm-gcc and not clang. But neither the complaint about the hype (and implication that it is thus not worth looking at) nor the original article are about Clang, they are about llvm. The ability to do IPO on large projects with llvm is not dependent on the C frontent (clang or llvm-gcc) you are using.

Overly Hyped

Posted Nov 14, 2008 18:54 UTC (Fri) by clugstj (subscriber, #4020) [Link]

Funny, "Clang" is the 4th word in the title of said article.

Overly Hyped

Posted Nov 20, 2008 14:24 UTC (Thu) by Nelson (subscriber, #21712) [Link]

Is that actually compiling the kernel code with LLVM? The man pages are a bit confusing, aren't the -S and -emit-llvm options required? It's not clear to me if that's just normal GCC or LLVM without the link time options.