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IA32: Add __divmoddi4/__divdi3/__moddi3 gcc intrinsics replacements #110

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IA32: Add __divmoddi4/__divdi3/__moddi3 gcc intrinsics replacements #110

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112 changes: 112 additions & 0 deletions lib/ia32/math.c
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Original file line number Diff line number Diff line change
Expand Up @@ -180,3 +180,115 @@ DivU64x32 (
return Dividend;
#endif
}

// gcc on IA32 emits these calls on i64 division, as it expects linking with libgcc
// NB: The assembly code was generated by Claude.
#if defined(__GNUC__) && defined(__MINGW32__)
__attribute__ ((__used__))
long long
__divmoddi4(
long long dividend,
long long divisor,
long long *remainder
)
{
long long quot, rem;
int cnt;

__asm__ (
// eax/edx = |dividend| (becomes quotient), ecx/ebx = |divisor|
"movl %[n], %%eax \n\t"
"movl %H[n], %%edx \n\t"
"movl %[d], %%ecx \n\t"
"movl %H[d], %%ebx \n\t"

"testl %%edx, %%edx \n\t"
"jns 1f \n\t"
"negl %%edx \n\t"
"negl %%eax \n\t"
"sbbl $0, %%edx \n\t"
"1: \n\t"
"testl %%ebx, %%ebx \n\t"
"jns 2f \n\t"
"negl %%ebx \n\t"
"negl %%ecx \n\t"
"sbbl $0, %%ebx \n\t"
"2: \n\t"

// edi:esi = running remainder = 0
"xorl %%esi, %%esi \n\t"
"xorl %%edi, %%edi \n\t"
"movl $64, %[c] \n\t"

// shift-subtract loop
"3: \n\t"
"shll $1, %%eax \n\t"
"rcll $1, %%edx \n\t"
"rcll $1, %%esi \n\t"
"rcll $1, %%edi \n\t"
"cmpl %%ebx, %%edi \n\t" // remainder >= divisor?
"jb 4f \n\t"
"ja 5f \n\t"
"cmpl %%ecx, %%esi \n\t"
"jb 4f \n\t"
"5: \n\t"
"subl %%ecx, %%esi \n\t"
"sbbl %%ebx, %%edi \n\t"
"orl $1, %%eax \n\t"
"4: \n\t"
"decl %[c] \n\t"
"jnz 3b \n\t"

// sign fixup: quotient negative if signs differ,
// remainder takes the sign of the dividend
"movl %H[n], %%ebx \n\t"
"movl %H[d], %%ecx \n\t"
"xorl %%ebx, %%ecx \n\t"
"jns 6f \n\t"
"negl %%edx \n\t"
"negl %%eax \n\t"
"sbbl $0, %%edx \n\t"
"6: \n\t"
"testl %%ebx, %%ebx \n\t"
"jns 7f \n\t"
"negl %%edi \n\t"
"negl %%esi \n\t"
"sbbl $0, %%edi \n\t"
"7: \n\t"

// store results
"movl %%eax, %[q] \n\t"
"movl %%edx, %H[q] \n\t"
"movl %%esi, %[r] \n\t"
"movl %%edi, %H[r] \n\t"
: [q] "=&m" (quot), [r] "=&m" (rem), [c] "=&m" (cnt)
: [n] "m" (dividend), [d] "m" (divisor)
: "eax", "ebx", "ecx", "edx", "esi", "edi", "cc"
);

if (remainder)
*remainder = rem;
return quot;
}

__attribute__ ((__used__))
long long
__divdi3(
long long dividend,
long long divisor
)
{
return __divmoddi4(dividend, divisor, 0);
}

long long
__moddi3(
long long dividend,
long long divisor
)
{
long long rem;
__divmoddi4(dividend, divisor, &rem);
return rem;
}
#endif
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