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Date: Sun, 01 Jan 2012 17:11:08 +0100
From: Dimitry Andric <dim@FreeBSD.org>
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To: Nathan Whitehorn <nwhitehorn@FreeBSD.org>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
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Subject: Re: svn commit: r229169 - head/lib/clang
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On 2012-01-01 16:56, Nathan Whitehorn wrote:
> Author: nwhitehorn
> Date: Sun Jan  1 15:56:15 2012
> New Revision: 229169
> URL: http://svn.freebsd.org/changeset/base/229169
>
> Log:
>    Instead of forcing -O1 on PowerPC for LLVM and clang, fix the actual
>    problem by adding -fno-strict-aliasing to CFLAGS. Since this is a global
>    issue that just happened to manifest on PowerPC, add this to CFLAGS
>    unconditionally.
>
>    MFC after:	1 week
>
> Modified:
>    head/lib/clang/clang.build.mk
>
> Modified: head/lib/clang/clang.build.mk
> ==============================================================================
> --- head/lib/clang/clang.build.mk	Sun Jan  1 09:12:21 2012	(r229168)
> +++ head/lib/clang/clang.build.mk	Sun Jan  1 15:56:15 2012	(r229169)
> @@ -8,10 +8,8 @@ CFLAGS+=-I${LLVM_SRCS}/include -I${CLANG
>   	-DLLVM_ON_UNIX -DLLVM_ON_FREEBSD \
>   	-D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS #-DNDEBUG
>
> -# Correct for gcc miscompilation when compiling on PPC with -O2
> -.if ${MACHINE_CPUARCH} == "powerpc"
> -CFLAGS+= -O1
> -.endif
> +# LLVM is not strict aliasing safe as of 12/31/2011
> +CFLAGS+= -fno-strict-aliasing

Actually, LLVM is strict-aliasing safe, but not for gcc 4.2.1. :)

There is some sort of problem with gcc's optimizer that made a few LLVM
tests fails mysteriously in the past.  At a certain point, these
problems went away for x86, but apparently not for non-x86...

In any case, this option should only have to be added when the compiler
is base gcc.