Mailing List Archive: libgcrypt-1.9.2: cipher/poly1305.c does not compile on i686/32 with gcc-4.7.3 ( --disable-asm does not work)

Hello!

The "#define ADD_1305_32" ( for "defined (__i386__) && __GNUC__ >= 4" )
leads to

> poly1305.c: In function 'poly1305_blocks':
> poly1305.c:424:7: error: can't find a register in class 'GENERAL_REGS'
> while
reloading 'asm'
> poly1305.c:424:7: error: 'asm' operand has impossible constraints

I suppose the template uses too many registers, so I redefined it and it
seems to
work for me ( all tests successful ).

hth
horst wente

--- cipher/poly1305.c.orig 2021-01-28 13:53:52.000000000 +0100
+++ cipher/poly1305.c 2021-03-01 20:25:26.000000000 +0100
@@ -314,14 +314,19 @@

/* A += B (i386) */
#define ADD_1305_32(A4, A3, A2, A1, A0, B4, B3, B2, B1, B0) \
- __asm__ ("addl %5, %0\n" \
- "adcl %6, %1\n" \
- "adcl %7, %2\n" \
- "adcl %8, %3\n" \
- "adcl %9, %4\n" \
- : "+r" (A0), "+r" (A1), "+r" (A2), "+r" (A3), "+r" (A4) \
- : "g" (B0), "g" (B1), "g" (B2), "g" (B3), "g" (B4) \
- : "cc" )
+ __asm__ ("clc\n" \
+ "addl %5, %0\n" \
+ "movl %6, %5\n" \
+ "adcl %5, %1\n" \
+ "movl %7, %5\n" \
+ "adcl %5, %2\n" \
+ "movl %8, %5\n" \
+ "adcl %5, %3\n" \
+ "movl %9, %5\n" \
+ "adcl %5, %4\n" \
+ : "+m" (A0), "+m" (A1), "+m" (A2), "+m" (A3), "+m" (A4)
\
+ : "r" (B0), "g" (B1), "g" (B2), "g" (B3), "g" (B4)
\
+ : "cc" )

#endif /* __i386__ */

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On 2.3.2021 1.02, horst.wente--- via Gcrypt-devel wrote:
> Hello!
>
> The "#define ADD_1305_32" ( for "defined (__i386__) && __GNUC__ >= 4" ) leads to
>
>> poly1305.c: In function 'poly1305_blocks':
>> poly1305.c:424:7: error: can't find a register in class 'GENERAL_REGS' while
>     reloading 'asm'
>> poly1305.c:424:7: error: 'asm' operand has impossible constraints
>
> I suppose the template uses too many registers, so I redefined it and it seems to
> work for me ( all tests successful ).
>

Thanks for reporting. I think it is better to just disable this macro for GCC-4.x
as any changes to asm operand types cause performance drop with newer GCC.
When ADD_1305_32 is not provided specific arch, generic version is used.

-Jussi

> hth
> horst wente
>
>
> --- cipher/poly1305.c.orig      2021-01-28 13:53:52.000000000 +0100
> +++ cipher/poly1305.c   2021-03-01 20:25:26.000000000 +0100
> @@ -314,14 +314,19 @@
>
> /* A += B (i386) */
> #define ADD_1305_32(A4, A3, A2, A1, A0, B4, B3, B2, B1, B0) \
> -      __asm__ ("addl %5, %0\n" \
> -              "adcl %6, %1\n" \
> -              "adcl %7, %2\n" \
> -              "adcl %8, %3\n" \
> -              "adcl %9, %4\n" \
> -              : "+r" (A0), "+r" (A1), "+r" (A2), "+r" (A3), "+r" (A4) \
> -              : "g" (B0), "g" (B1), "g" (B2), "g" (B3), "g" (B4) \
> -              : "cc" )
> +      __asm__ ("clc\n"         \
> +               "addl %5, %0\n" \
> +               "movl %6, %5\n" \
> +               "adcl %5, %1\n" \
> +               "movl %7, %5\n" \
> +               "adcl %5, %2\n" \
> +               "movl %8, %5\n" \
> +               "adcl %5, %3\n" \
> +               "movl %9, %5\n" \
> +               "adcl %5, %4\n" \
> +               : "+m" (A0), "+m" (A1), "+m" (A2), "+m" (A3), "+m" (A4) \
> +               : "r" (B0), "g" (B1), "g" (B2), "g" (B3), "g" (B4) \
> +               : "cc" )
>
> #endif /* __i386__ */
>
>
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