On FreeBSD, the arch in the arch-vendor-os triple is usually 'amd64'
instead of 'x86_64', e.g. amd64-unknown-freebsd9.0.
If somebody uses such a triple, the code in Clang::AddX86TargetArgs()
does not recognize the arch, so the default CPU name is not set to
x86-64, and interesting things can then happen.
In my case, clang assumed an incorrect 16-byte alignment for some global
structs, and started accessing them with SSE movaps instructions,
leading to bus errors at runtime, because the structs were really 8-byte
aligned.
I would like to propose the attached patch, which makes clang recognize
both 'amd64' and 'x86_64', at least for FreeBSD. Maybe this can also be
used for other operating systems, if that is desirable.
Index: tools/clang/lib/Driver/Tools.cpp
===================================================================
--- tools/clang/lib/Driver/Tools.cpp (revision 131958)
+++ tools/clang/lib/Driver/Tools.cpp (working copy)
@@ -777,7 +777,8 @@ void Clang::AddX86TargetArgs(const ArgList &Args,
else if (getToolChain().getArchName() == "i386")
CPUName = "i486";
} else if (getToolChain().getOS().startswith("freebsd")) {
- if (getToolChain().getArchName() == "x86_64")
+ if (getToolChain().getArchName() == "amd64" ||
+ getToolChain().getArchName() == "x86_64")
CPUName = "x86-64";
else if (getToolChain().getArchName() == "i386")
CPUName = "i486";
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