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author | Rich Felker <dalias@aerifal.cx> | 2019-05-11 19:44:21 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2019-05-11 19:44:21 -0400 |
commit | bdb0817599325e6ca6838717dfe18290695a59a2 (patch) | |
tree | 9ec908dfc35ac48bef7bf19126147289a3561eb2 | |
parent | c8798ef974d21c338a7d8d874a402978ffc6168e (diff) | |
download | musl-bdb0817599325e6ca6838717dfe18290695a59a2.tar.gz musl-bdb0817599325e6ca6838717dfe18290695a59a2.tar.bz2 musl-bdb0817599325e6ca6838717dfe18290695a59a2.tar.xz musl-bdb0817599325e6ca6838717dfe18290695a59a2.zip |
improve i386 inline syscall asm on non-broken compilers
we have to avoid using ebx unconditionally in asm constraints for
i386, because gcc 3 and 4 and possibly other simplistic compilers
(pcc?) implement PIC via making ebx a fixed-use register, and disallow
its use for anything else. rather than hard-coding knowledge of which
compilers work (at least gcc 5+ and clang), perform a configure test;
this should give us the good codegen on any new compilers we don't yet
know about.
swapping ebx and edx is kept for 1- and 2-arg syscalls because it
avoids having any spills/stack-frame at all in small functions. for
6-arg, if ebx is directly usable, the complex shuffling introduced in
commit c8798ef974d21c338a7d8d874a402978ffc6168e can be avoided, and
ebp can be loaded the same way ebx is in 5-arg syscalls for compilers
that don't support direct use of ebx.
-rw-r--r-- | arch/i386/syscall_arch.h | 21 | ||||
-rwxr-xr-x | configure | 14 |
2 files changed, 34 insertions, 1 deletions
diff --git a/arch/i386/syscall_arch.h b/arch/i386/syscall_arch.h index 29e141f2..22b0b28b 100644 --- a/arch/i386/syscall_arch.h +++ b/arch/i386/syscall_arch.h @@ -36,30 +36,49 @@ static inline long __syscall2(long n, long a1, long a2) static inline long __syscall3(long n, long a1, long a2, long a3) { unsigned long __ret; +#if !defined(__PIC__) || !defined(BROKEN_EBX_ASM) + __asm__ __volatile__ (SYSCALL_INSNS : "=a"(__ret) : "a"(n), "b"(a1), "c"(a2), "d"(a3) : "memory"); +#else __asm__ __volatile__ (SYSCALL_INSNS_34 : "=a"(__ret) : "a"(n), "D"(a1), "c"(a2), "d"(a3) : "memory"); +#endif return __ret; } static inline long __syscall4(long n, long a1, long a2, long a3, long a4) { unsigned long __ret; +#if !defined(__PIC__) || !defined(BROKEN_EBX_ASM) + __asm__ __volatile__ (SYSCALL_INSNS : "=a"(__ret) : "a"(n), "b"(a1), "c"(a2), "d"(a3), "S"(a4) : "memory"); +#else __asm__ __volatile__ (SYSCALL_INSNS_34 : "=a"(__ret) : "a"(n), "D"(a1), "c"(a2), "d"(a3), "S"(a4) : "memory"); +#endif return __ret; } static inline long __syscall5(long n, long a1, long a2, long a3, long a4, long a5) { unsigned long __ret; +#if !defined(__PIC__) || !defined(BROKEN_EBX_ASM) + __asm__ __volatile__ (SYSCALL_INSNS + : "=a"(__ret) : "a"(n), "b"(a1), "c"(a2), "d"(a3), "S"(a4), "D"(a5) : "memory"); +#else __asm__ __volatile__ ("pushl %2 ; push %%ebx ; mov 4(%%esp),%%ebx ; " SYSCALL_INSNS " ; pop %%ebx ; add $4,%%esp" : "=a"(__ret) : "a"(n), "g"(a1), "c"(a2), "d"(a3), "S"(a4), "D"(a5) : "memory"); +#endif return __ret; } static inline long __syscall6(long n, long a1, long a2, long a3, long a4, long a5, long a6) { - unsigned long __ret, a1a6[2] = { a1, a6 }; + unsigned long __ret; +#if !defined(__PIC__) || !defined(BROKEN_EBX_ASM) + __asm__ __volatile__ ("pushl %7 ; push %%ebp ; mov 4(%%esp),%%ebp ; " SYSCALL_INSNS " ; pop %%ebp ; add $4,%%esp" + : "=a"(__ret) : "a"(n), "b"(a1), "c"(a2), "d"(a3), "S"(a4), "D"(a5), "g"(a6) : "memory"); +#else + unsigned long a1a6[2] = { a1, a6 }; __asm__ __volatile__ ("pushl %1 ; push %%ebx ; push %%ebp ; mov 8(%%esp),%%ebx ; mov 4(%%ebx),%%ebp ; mov (%%ebx),%%ebx ; " SYSCALL_INSNS " ; pop %%ebp ; pop %%ebx ; add $4,%%esp" : "=a"(__ret) : "g"(&a1a6), "a"(n), "c"(a2), "d"(a3), "S"(a4), "D"(a5) : "memory"); +#endif return __ret; } @@ -573,6 +573,20 @@ printf "using compiler runtime libraries: %s\n" "$LIBCC" SUBARCH= t="$CFLAGS_C99FSE $CPPFLAGS $CFLAGS" +if test "$ARCH" = "i386" ; then +printf "checking whether compiler can use ebx in PIC asm constraints... " +cat > "$tmpc" <<EOF +int foo(int x) { __asm__ ( "" : "+b"(x) ); return x; } +EOF +if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS -fPIC \ + -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then +printf "yes\n" +else +printf "no\n" +CFLAGS_AUTO="$CFLAGS_AUTO -DBROKEN_EBX_ASM" +fi +fi + if test "$ARCH" = "x86_64" ; then trycppif __ILP32__ "$t" && ARCH=x32 fi |