;

; jquant.asm - sample data conversion and quantization (MMX)

;

; Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB</ossman@cendio.se>

; Copyright (C) 2016, D. R. Commander.

;

; Based on the x86 SIMD extension for IJG JPEG library

; Copyright (C) 1999-2006, MIYASAKA Masaru.

; For conditions of distribution and use, see copyright notice in jsimdext.inc

;

; This file should be assembled with NASM (Netwide Assembler),

; can *not* be assembled with Microsoft's MASM or any compatible

; assembler (including Borland's Turbo Assembler).

; NASM is available from http://nasm.sourceforge.net/ or

; http://sourceforge.net/project/showfiles.php?group_id=6208

%include "jsimdext.inc"

%include "jdct.inc"

; --------------------------------------------------------------------------

    SECTION     SEG_TEXT

    BITS        32

;

; Load data into workspace, applying unsigned->signed conversion

;

; GLOBAL(void)

; jsimd_convsamp_mmx(JSAMPARRAY sample_data, JDIMENSION start_col,

;                    DCTELEM *workspace);

;

%define sample_data  ebp + 8            ; JSAMPARRAY sample_data

%define start_col    ebp + 12           ; JDIMENSION start_col

%define workspace    ebp + 16           ; DCTELEM *workspace

    align       32

    GLOBAL_FUNCTION(jsimd_convsamp_mmx)

EXTN(jsimd_convsamp_mmx):

    push        ebp

    mov         ebp, esp

    push        ebx

;   push        ecx                     ; need not be preserved

;   push        edx                     ; need not be preserved

    push        esi

    push        edi

    pxor        mm6, mm6                ; mm6=(all 0's)

    pcmpeqw     mm7, mm7

    psllw       mm7, 7                  ; mm7={0xFF80 0xFF80 0xFF80 0xFF80}

    mov         esi, JSAMPARRAY [sample_data]  ; (JSAMPROW *)

    mov         eax, JDIMENSION [start_col]

    mov         edi, POINTER [workspace]       ; (DCTELEM *)

    mov         ecx, DCTSIZE/4

    alignx      16, 7

.convloop:

    mov         ebx, JSAMPROW [esi+0*SIZEOF_JSAMPROW]  ; (JSAMPLE *)

    mov         edx, JSAMPROW [esi+1*SIZEOF_JSAMPROW]  ; (JSAMPLE *)

    movq        mm0, MMWORD [ebx+eax*SIZEOF_JSAMPLE]   ; mm0=(01234567)

    movq        mm1, MMWORD [edx+eax*SIZEOF_JSAMPLE]   ; mm1=(89ABCDEF)

    mov         ebx, JSAMPROW [esi+2*SIZEOF_JSAMPROW]  ; (JSAMPLE *)

    mov         edx, JSAMPROW [esi+3*SIZEOF_JSAMPROW]  ; (JSAMPLE *)

    movq        mm2, MMWORD [ebx+eax*SIZEOF_JSAMPLE]   ; mm2=(GHIJKLMN)

    movq        mm3, MMWORD [edx+eax*SIZEOF_JSAMPLE]   ; mm3=(OPQRSTUV)

    movq        mm4, mm0

    punpcklbw   mm0, mm6                ; mm0=(0123)

    punpckhbw   mm4, mm6                ; mm4=(4567)

    movq        mm5, mm1

    punpcklbw   mm1, mm6                ; mm1=(89AB)

    punpckhbw   mm5, mm6                ; mm5=(CDEF)

    paddw       mm0, mm7

    paddw       mm4, mm7

    paddw       mm1, mm7

    paddw       mm5, mm7

    movq        MMWORD [MMBLOCK(0,0,edi,SIZEOF_DCTELEM)], mm0

    movq        MMWORD [MMBLOCK(0,1,edi,SIZEOF_DCTELEM)], mm4

    movq        MMWORD [MMBLOCK(1,0,edi,SIZEOF_DCTELEM)], mm1

    movq        MMWORD [MMBLOCK(1,1,edi,SIZEOF_DCTELEM)], mm5

    movq        mm0, mm2

    punpcklbw   mm2, mm6                ; mm2=(GHIJ)

    punpckhbw   mm0, mm6                ; mm0=(KLMN)

    movq        mm4, mm3

    punpcklbw   mm3, mm6                ; mm3=(OPQR)

    punpckhbw   mm4, mm6                ; mm4=(STUV)

    paddw       mm2, mm7

    paddw       mm0, mm7

    paddw       mm3, mm7

    paddw       mm4, mm7

    movq        MMWORD [MMBLOCK(2,0,edi,SIZEOF_DCTELEM)], mm2

    movq        MMWORD [MMBLOCK(2,1,edi,SIZEOF_DCTELEM)], mm0

    movq        MMWORD [MMBLOCK(3,0,edi,SIZEOF_DCTELEM)], mm3

    movq        MMWORD [MMBLOCK(3,1,edi,SIZEOF_DCTELEM)], mm4

    add         esi, byte 4*SIZEOF_JSAMPROW

    add         edi, byte 4*DCTSIZE*SIZEOF_DCTELEM

    dec         ecx

    jnz         short .convloop

    emms                                ; empty MMX state

    pop         edi

    pop         esi

;   pop         edx                     ; need not be preserved

;   pop         ecx                     ; need not be preserved

    pop         ebx

    pop         ebp

    ret

; --------------------------------------------------------------------------

;

; Quantize/descale the coefficients, and store into coef_block

;

; This implementation is based on an algorithm described in

;   "How to optimize for the Pentium family of microprocessors"

;   (http://www.agner.org/assem/).

;

; GLOBAL(void)

; jsimd_quantize_mmx(JCOEFPTR coef_block, DCTELEM *divisors,

;                    DCTELEM *workspace);

;

%define RECIPROCAL(m, n, b) \

  MMBLOCK(DCTSIZE * 0 + (m), (n), (b), SIZEOF_DCTELEM)

%define CORRECTION(m, n, b) \

  MMBLOCK(DCTSIZE * 1 + (m), (n), (b), SIZEOF_DCTELEM)

%define SCALE(m, n, b) \

  MMBLOCK(DCTSIZE * 2 + (m), (n), (b), SIZEOF_DCTELEM)

%define SHIFT(m, n, b) \

  MMBLOCK(DCTSIZE * 3 + (m), (n), (b), SIZEOF_DCTELEM)

%define coef_block  ebp + 8             ; JCOEFPTR coef_block

%define divisors    ebp + 12            ; DCTELEM *divisors

%define workspace   ebp + 16            ; DCTELEM *workspace

    align       32

    GLOBAL_FUNCTION(jsimd_quantize_mmx)

EXTN(jsimd_quantize_mmx):

    push        ebp

    mov         ebp, esp

;   push        ebx                     ; unused

;   push        ecx                     ; unused

;   push        edx                     ; need not be preserved

    push        esi

    push        edi

    mov         esi, POINTER [workspace]

    mov         edx, POINTER [divisors]

    mov         edi, JCOEFPTR [coef_block]

    mov         ah, 2

    alignx      16, 7

.quantloop1:

    mov         al, DCTSIZE2/8/2

    alignx      16, 7

.quantloop2:

    movq        mm2, MMWORD [MMBLOCK(0,0,esi,SIZEOF_DCTELEM)]

    movq        mm3, MMWORD [MMBLOCK(0,1,esi,SIZEOF_DCTELEM)]

    movq        mm0, mm2

    movq        mm1, mm3

    psraw       mm2, (WORD_BIT-1)       ; -1 if value < 0, 0 otherwise

    psraw       mm3, (WORD_BIT-1)

    pxor        mm0, mm2                ; val = -val

    pxor        mm1, mm3

    psubw       mm0, mm2

    psubw       mm1, mm3

    ;

    ; MMX is an annoyingly crappy instruction set. It has two

    ; misfeatures that are causing problems here:

    ;

    ; - All multiplications are signed.

    ;

    ; - The second operand for the shifts is not treated as packed.

    ;

    ;

    ; We work around the first problem by implementing this algorithm:

    ;

    ; unsigned long unsigned_multiply(unsigned short x, unsigned short y)

    ; {

    ;   enum { SHORT_BIT = 16 };

    ;   signed short sx = (signed short)x;

    ;   signed short sy = (signed short)y;

    ;   signed long sz;

    ;

    ;   sz = (long)sx * (long)sy;    /* signed multiply */

    ;

    ;   if (sx < 0) sz += (long)sy << SHORT_BIT;

    ;   if (sy < 0) sz += (long)sx << SHORT_BIT;

    ;

    ;   return (unsigned long)sz;

    ; }

    ;

    ; (note that a negative sx adds _sy_ and vice versa)

    ;

    ; For the second problem, we replace the shift by a multiplication.

    ; Unfortunately that means we have to deal with the signed issue again.

    ;

    paddw       mm0, MMWORD [CORRECTION(0,0,edx)]  ; correction + roundfactor

    paddw       mm1, MMWORD [CORRECTION(0,1,edx)]

    movq        mm4, mm0                ; store current value for later

    movq        mm5, mm1

    pmulhw      mm0, MMWORD [RECIPROCAL(0,0,edx)]  ; reciprocal

    pmulhw      mm1, MMWORD [RECIPROCAL(0,1,edx)]

    paddw       mm0, mm4  ; reciprocal is always negative (MSB=1),

    paddw       mm1, mm5  ; so we always need to add the initial value

                          ; (input value is never negative as we

                          ; inverted it at the start of this routine)

    ; here it gets a bit tricky as both scale

    ; and mm0/mm1 can be negative

    movq        mm6, MMWORD [SCALE(0,0,edx)]  ; scale

    movq        mm7, MMWORD [SCALE(0,1,edx)]

    movq        mm4, mm0

    movq        mm5, mm1

    pmulhw      mm0, mm6

    pmulhw      mm1, mm7

    psraw       mm6, (WORD_BIT-1)       ; determine if scale is negative

    psraw       mm7, (WORD_BIT-1)

    pand        mm6, mm4                ; and add input if it is

    pand        mm7, mm5

    paddw       mm0, mm6

    paddw       mm1, mm7

    psraw       mm4, (WORD_BIT-1)       ; then check if negative input

    psraw       mm5, (WORD_BIT-1)

    pand        mm4, MMWORD [SCALE(0,0,edx)]  ; and add scale if it is

    pand        mm5, MMWORD [SCALE(0,1,edx)]

    paddw       mm0, mm4

    paddw       mm1, mm5

    pxor        mm0, mm2                ; val = -val

    pxor        mm1, mm3

    psubw       mm0, mm2

    psubw       mm1, mm3

    movq        MMWORD [MMBLOCK(0,0,edi,SIZEOF_DCTELEM)], mm0

    movq        MMWORD [MMBLOCK(0,1,edi,SIZEOF_DCTELEM)], mm1

    add         esi, byte 8*SIZEOF_DCTELEM

    add         edx, byte 8*SIZEOF_DCTELEM

    add         edi, byte 8*SIZEOF_JCOEF

    dec         al

    jnz         near .quantloop2

    dec         ah

    jnz         near .quantloop1        ; to avoid branch misprediction

    emms                                ; empty MMX state

    pop         edi

    pop         esi

;   pop         edx                     ; need not be preserved

;   pop         ecx                     ; unused

;   pop         ebx                     ; unused

    pop         ebp

    ret

; For some reason, the OS X linker does not honor the request to align the

; segment unless we do this.

    align       32