diff options
Diffstat (limited to 'MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm')
| -rw-r--r-- | MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm b/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm index 61a53d1e3a..95e57efac1 100644 --- a/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm +++ b/MdePkg/Library/BaseLib/Ia32/DivU64x64Remainder.asm @@ -36,13 +36,13 @@ EXTERN InternalMathDivRemU64x32:PROC ; );
;------------------------------------------------------------------------------
InternalMathDivRemU64x64 PROC
- mov ecx, [esp + 16]
+ mov ecx, [esp + 16] ; ecx <- divisor[32..63]
test ecx, ecx
jnz _@DivRemU64x64 ; call _@DivRemU64x64 if Divisor > 2^32
mov ecx, [esp + 20]
jecxz @F
- and dword ptr [ecx + 4], 0
- mov [esp + 16], ecx
+ and dword ptr [ecx + 4], 0 ; zero high dword of remainder
+ mov [esp + 16], ecx ; set up stack frame to match DivRemU64x32
@@:
jmp InternalMathDivRemU64x32
InternalMathDivRemU64x64 ENDP
@@ -61,11 +61,11 @@ _@DivRemU64x64 PROC USES ebx esi edi jnz @B
div ebx
mov ebx, eax ; ebx <- quotient
- mov ecx, [esp + 28]
- mul dword ptr [esp + 24]
- imul ecx, ebx
- add edx, ecx
- mov ecx, dword ptr [esp + 32]
+ mov ecx, [esp + 28] ; ecx <- high dword of divisor
+ mul dword ptr [esp + 24] ; edx:eax <- quotient * divisor[0..31]
+ imul ecx, ebx ; ecx <- quotient * divisor[32..63]
+ add edx, ecx ; edx <- (quotient * divisor)[32..63]
+ mov ecx, dword ptr [esp + 32] ; ecx <- addr for Remainder
jc @TooLarge ; product > 2^64
cmp edi, edx ; compare high 32 bits
ja @Correct
@@ -76,7 +76,7 @@ _@DivRemU64x64 PROC USES ebx esi edi dec ebx ; adjust quotient by -1
jecxz @Return ; return if Remainder == NULL
sub eax, dword ptr [esp + 24]
- sbb edx, dword ptr [esp + 28]
+ sbb edx, dword ptr [esp + 28] ; edx:eax <- (quotient - 1) * divisor
@Correct:
jecxz @Return
sub esi, eax
@@ -85,7 +85,7 @@ _@DivRemU64x64 PROC USES ebx esi edi mov [ecx + 4], edi
@Return:
mov eax, ebx ; eax <- quotient
- xor edx, edx
+ xor edx, edx ; quotient is 32 bits long
ret
_@DivRemU64x64 ENDP
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