;
; jccolext.asm - colorspace conversion (64-bit SSE2)
;
; Copyright (C) 2009, 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
;
; [TAB8]
%include "jcolsamp.inc"
; --------------------------------------------------------------------------
;
; Convert some rows of samples to the output colorspace.
;
; GLOBAL(void)
; jsimd_rgb_ycc_convert_sse2 (JDIMENSION img_width,
; JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
; JDIMENSION output_row, int num_rows);
;
; r10 = JDIMENSION img_width
; r11 = JSAMPARRAY input_buf
; r12 = JSAMPIMAGE output_buf
; r13 = JDIMENSION output_row
; r14 = int num_rows
%define wk(i) rbp-(WK_NUM-(i))*SIZEOF_XMMWORD ; xmmword wk[WK_NUM]
%define WK_NUM 8
align 16
global EXTN(jsimd_rgb_ycc_convert_sse2)
EXTN(jsimd_rgb_ycc_convert_sse2):
push rbp
mov rax,rsp ; rax = original rbp
sub rsp, byte 4
and rsp, byte (-SIZEOF_XMMWORD) ; align to 128 bits
mov [rsp],rax
mov rbp,rsp ; rbp = aligned rbp
lea rsp, [wk(0)]
collect_args
push rbx
mov ecx, r10d
test rcx,rcx
jz near .return
push rcx
mov rsi, r12
mov ecx, r13d
mov rdi, JSAMPARRAY [rsi+0*SIZEOF_JSAMPARRAY]
mov rbx, JSAMPARRAY [rsi+1*SIZEOF_JSAMPARRAY]
mov rdx, JSAMPARRAY [rsi+2*SIZEOF_JSAMPARRAY]
lea rdi, [rdi+rcx*SIZEOF_JSAMPROW]
lea rbx, [rbx+rcx*SIZEOF_JSAMPROW]
lea rdx, [rdx+rcx*SIZEOF_JSAMPROW]
pop rcx
mov rsi, r11
mov eax, r14d
test rax,rax
jle near .return
.rowloop:
push rdx
push rbx
push rdi
push rsi
push rcx ; col
mov rsi, JSAMPROW [rsi] ; inptr
mov rdi, JSAMPROW [rdi] ; outptr0
mov rbx, JSAMPROW [rbx] ; outptr1
mov rdx, JSAMPROW [rdx] ; outptr2
cmp rcx, byte SIZEOF_XMMWORD
jae near .columnloop
%if RGB_PIXELSIZE == 3 ; ---------------
.column_ld1:
push rax
push rdx
lea rcx,[rcx+rcx*2] ; imul ecx,RGB_PIXELSIZE
test cl, SIZEOF_BYTE
jz short .column_ld2
sub rcx, byte SIZEOF_BYTE
movzx rax, BYTE [rsi+rcx]
.column_ld2:
test cl, SIZEOF_WORD
jz short .column_ld4
sub rcx, byte SIZEOF_WORD
movzx rdx, WORD [rsi+rcx]
shl rax, WORD_BIT
or rax,rdx
.column_ld4:
movd xmmA,eax
pop rdx
pop rax
test cl, SIZEOF_DWORD
jz short .column_ld8
sub rcx, byte SIZEOF_DWORD
movd xmmF, XMM_DWORD [rsi+rcx]
pslldq xmmA, SIZEOF_DWORD
por xmmA,xmmF
.column_ld8:
test cl, SIZEOF_MMWORD
jz short .column_ld16
sub rcx, byte SIZEOF_MMWORD
movq xmmB, XMM_MMWORD [rsi+rcx]
pslldq xmmA, SIZEOF_MMWORD
por xmmA,xmmB
.column_ld16:
test cl, SIZEOF_XMMWORD
jz short .column_ld32
movdqa xmmF,xmmA
movdqu xmmA, XMMWORD [rsi+0*SIZEOF_XMMWORD]
mov rcx, SIZEOF_XMMWORD
jmp short .rgb_ycc_cnv
.column_ld32:
test cl, 2*SIZEOF_XMMWORD
mov rcx, SIZEOF_XMMWORD
jz short .rgb_ycc_cnv
movdqa xmmB,xmmA
movdqu xmmA, XMMWORD [rsi+0*SIZEOF_XMMWORD]
movdqu xmmF, XMMWORD [rsi+1*SIZEOF_XMMWORD]
jmp short .rgb_ycc_cnv
.columnloop:
movdqu xmmA, XMMWORD [rsi+0*SIZEOF_XMMWORD]
movdqu xmmF, XMMWORD [rsi+1*SIZEOF_XMMWORD]
movdqu xmmB, XMMWORD [rsi+2*SIZEOF_XMMWORD]
.rgb_ycc_cnv:
; xmmA=(00 10 20 01 11 21 02 12 22 03 13 23 04 14 24 05)
; xmmF=(15 25 06 16 26 07 17 27 08 18 28 09 19 29 0A 1A)
; xmmB=(2A 0B 1B 2B 0C 1C 2C 0D 1D 2D 0E 1E 2E 0F 1F 2F)
movdqa xmmG,xmmA
pslldq xmmA,8 ; xmmA=(-- -- -- -- -- -- -- -- 00 10 20 01 11 21 02 12)
psrldq xmmG,8 ; xmmG=(22 03 13 23 04 14 24 05 -- -- -- -- -- -- -- --)
punpckhbw xmmA,xmmF ; xmmA=(00 08 10 18 20 28 01 09 11 19 21 29 02 0A 12 1A)
pslldq xmmF,8 ; xmmF=(-- -- -- -- -- -- -- -- 15 25 06 16 26 07 17 27)
punpcklbw xmmG,xmmB ; xmmG=(22 2A 03 0B 13 1B 23 2B 04 0C 14 1C 24 2C 05 0D)
punpckhbw xmmF,xmmB ; xmmF=(15 1D 25 2D 06 0E 16 1E 26 2E 07 0F 17 1F 27 2F)
movdqa xmmD,xmmA
pslldq xmmA,8 ; xmmA=(-- -- -- -- -- -- -- -- 00 08 10 18 20 28 01 09)
psrldq xmmD,8 ; xmmD=(11 19 21 29 02 0A 12 1A -- -- -- -- -- -- -- --)
punpckhbw xmmA,xmmG ; xmmA=(00 04 08 0C 10 14 18 1C 20 24 28 2C 01 05 09 0D)
pslldq xmmG,8 ; xmmG=(-- -- -- -- -- -- -- -- 22 2A 03 0B 13 1B 23 2B)
punpcklbw xmmD,xmmF ; xmmD=(11 15 19 1D 21 25 29 2D 02 06 0A 0E 12 16 1A 1E)
punpckhbw xmmG,xmmF ; xmmG=(22 26 2A 2E 03 07 0B 0F 13 17 1B 1F 23 27 2B 2F)
movdqa xmmE,xmmA
pslldq xmmA,8 ; xmmA=(-- -- -- -- -- -- -- -- 00 04 08 0C 10 14 18 1C)
psrldq xmmE,8 ; xmmE=(20 24 28 2C 01 05 09 0D -- -- -- -- -- -- -- --)
punpckhbw xmmA,xmmD ; xmmA=(00 02 04 06 08 0A 0C 0E 10 12 14 16 18 1A 1C 1E)
pslldq xmmD,8 ; xmmD=(-- -- -- -- -- -- -- -- 11 15 19 1D 21 25 29 2D)
punpcklbw xmmE,xmmG ; xmmE=(20 22 24 26 28 2A 2C 2E 01 03 05 07 09 0B 0D 0F)
punpckhbw xmmD,xmmG ; xmmD=(11 13 15 17 19 1B 1D 1F 21 23 25 27 29 2B 2D 2F)
pxor xmmH,xmmH
movdqa xmmC,xmmA
punpcklbw xmmA,xmmH ; xmmA=(00 02 04 06 08 0A 0C 0E)
punpckhbw xmmC,xmmH ; xmmC=(10 12 14 16 18 1A 1C 1E)
movdqa xmmB,xmmE
punpcklbw xmmE,xmmH ; xmmE=(20 22 24 26 28 2A 2C 2E)
punpckhbw xmmB,xmmH ; xmmB=(01 03 05 07 09 0B 0D 0F)
movdqa xmmF,xmmD
punpcklbw xmmD,xmmH ; xmmD=(11 13 15 17 19 1B 1D 1F)
punpckhbw xmmF,xmmH ; xmmF=(21 23 25 27 29 2B 2D 2F)
%else ; RGB_PIXELSIZE == 4 ; -----------
.column_ld1:
test cl, SIZEOF_XMMWORD/16
jz short .column_ld2
sub rcx, byte SIZEOF_XMMWORD/16
movd xmmA, XMM_DWORD [rsi+rcx*RGB_PIXELSIZE]
.column_ld2:
test cl, SIZEOF_XMMWORD/8
jz short .column_ld4
sub rcx, byte SIZEOF_XMMWORD/8
movq xmmE, XMM_MMWORD [rsi+rcx*RGB_PIXELSIZE]
pslldq xmmA, SIZEOF_MMWORD
por xmmA,xmmE
.column_ld4:
test cl, SIZEOF_XMMWORD/4
jz short .column_ld8
sub rcx, byte SIZEOF_XMMWORD/4
movdqa xmmE,xmmA
movdqu xmmA, XMMWORD [rsi+rcx*RGB_PIXELSIZE]
.column_ld8:
test cl, SIZEOF_XMMWORD/2
mov rcx, SIZEOF_XMMWORD
jz short .rgb_ycc_cnv
movdqa xmmF,xmmA
movdqa xmmH,xmmE
movdqu xmmA, XMMWORD [rsi+0*SIZEOF_XMMWORD]
movdqu xmmE, XMMWORD [rsi+1*SIZEOF_XMMWORD]
jmp short .rgb_ycc_cnv
.columnloop:
movdqu xmmA, XMMWORD [rsi+0*SIZEOF_XMMWORD]
movdqu xmmE, XMMWORD [rsi+1*SIZEOF_XMMWORD]
movdqu xmmF, XMMWORD [rsi+2*SIZEOF_XMMWORD]
movdqu xmmH, XMMWORD [rsi+3*SIZEOF_XMMWORD]
.rgb_ycc_cnv:
; xmmA=(00 10 20 30 01 11 21 31 02 12 22 32 03 13 23 33)
; xmmE=(04 14 24 34 05 15 25 35 06 16 26 36 07 17 27 37)
; xmmF=(08 18 28 38 09 19 29 39 0A 1A 2A 3A 0B 1B 2B 3B)
; xmmH=(0C 1C 2C 3C 0D 1D 2D 3D 0E 1E 2E 3E 0F 1F 2F 3F)
movdqa xmmD,xmmA
punpcklbw xmmA,xmmE ; xmmA=(00 04 10 14 20 24 30 34 01 05 11 15 21 25 31 35)
punpckhbw xmmD,xmmE ; xmmD=(02 06 12 16 22 26 32 36 03 07 13 17 23 27 33 37)
movdqa xmmC,xmmF
punpcklbw xmmF,xmmH ; xmmF=(08 0C 18 1C 28 2C 38 3C 09 0D 19 1D 29 2D 39 3D)
punpckhbw xmmC,xmmH ; xmmC=(0A 0E 1A 1E 2A 2E 3A 3E 0B 0F 1B 1F 2B 2F 3B 3F)
movdqa xmmB,xmmA
punpcklwd xmmA,xmmF ; xmmA=(00 04 08 0C 10 14 18 1C 20 24 28 2C 30 34 38 3C)
punpckhwd xmmB,xmmF ; xmmB=(01 05 09 0D 11 15 19 1D 21 25 29 2D 31 35 39 3D)
movdqa xmmG,xmmD
punpcklwd xmmD,xmmC ; xmmD=(02 06 0A 0E 12 16 1A 1E 22 26 2A 2E 32 36 3A 3E)
punpckhwd xmmG,xmmC ; xmmG=(03 07 0B 0F 13 17 1B 1F 23 27 2B 2F 33 37 3B 3F)
movdqa xmmE,xmmA
punpcklbw xmmA,xmmD ; xmmA=(00 02 04 06 08 0A 0C 0E 10 12 14 16 18 1A 1C 1E)
punpckhbw xmmE,xmmD ; xmmE=(20 22 24 26 28 2A 2C 2E 30 32 34 36 38 3A 3C 3E)
movdqa xmmH,xmmB
punpcklbw xmmB,xmmG ; xmmB=(01 03 05 07 09 0B 0D 0F 11 13 15 17 19 1B 1D 1F)
punpckhbw xmmH,xmmG ; xmmH=(21 23 25 27 29 2B 2D 2F 31 33 35 37 39 3B 3D 3F)
pxor xmmF,xmmF
movdqa xmmC,xmmA
punpcklbw xmmA,xmmF ; xmmA=(00 02 04 06 08 0A 0C 0E)
punpckhbw xmmC,xmmF ; xmmC=(10 12 14 16 18 1A 1C 1E)
movdqa xmmD,xmmB
punpcklbw xmmB,xmmF ; xmmB=(01 03 05 07 09 0B 0D 0F)
punpckhbw xmmD,xmmF ; xmmD=(11 13 15 17 19 1B 1D 1F)
movdqa xmmG,xmmE
punpcklbw xmmE,xmmF ; xmmE=(20 22 24 26 28 2A 2C 2E)
punpckhbw xmmG,xmmF ; xmmG=(30 32 34 36 38 3A 3C 3E)
punpcklbw xmmF,xmmH
punpckhbw xmmH,xmmH
psrlw xmmF,BYTE_BIT ; xmmF=(21 23 25 27 29 2B 2D 2F)
psrlw xmmH,BYTE_BIT ; xmmH=(31 33 35 37 39 3B 3D 3F)
%endif ; RGB_PIXELSIZE ; ---------------
; xmm0=R(02468ACE)=RE, xmm2=G(02468ACE)=GE, xmm4=B(02468ACE)=BE
; xmm1=R(13579BDF)=RO, xmm3=G(13579BDF)=GO, xmm5=B(13579BDF)=BO
; (Original)
; Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
; Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
; Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
;
; (This implementation)
; Y = 0.29900 * R + 0.33700 * G + 0.11400 * B + 0.25000 * G
; Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
; Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
movdqa XMMWORD [wk(0)], xmm0 ; wk(0)=RE
movdqa XMMWORD [wk(1)], xmm1 ; wk(1)=RO
movdqa XMMWORD [wk(2)], xmm4 ; wk(2)=BE
movdqa XMMWORD [wk(3)], xmm5 ; wk(3)=BO
movdqa xmm6,xmm1
punpcklwd xmm1,xmm3
punpckhwd xmm6,xmm3
movdqa xmm7,xmm1
movdqa xmm4,xmm6
pmaddwd xmm1,[rel PW_F0299_F0337] ; xmm1=ROL*FIX(0.299)+GOL*FIX(0.337)
pmaddwd xmm6,[rel PW_F0299_F0337] ; xmm6=ROH*FIX(0.299)+GOH*FIX(0.337)
pmaddwd xmm7,[rel PW_MF016_MF033] ; xmm7=ROL*-FIX(0.168)+GOL*-FIX(0.331)
pmaddwd xmm4,[rel PW_MF016_MF033] ; xmm4=ROH*-FIX(0.168)+GOH*-FIX(0.331)
movdqa XMMWORD [wk(4)], xmm1 ; wk(4)=ROL*FIX(0.299)+GOL*FIX(0.337)
movdqa XMMWORD [wk(5)], xmm6 ; wk(5)=ROH*FIX(0.299)+GOH*FIX(0.337)
pxor xmm1,xmm1
pxor xmm6,xmm6
punpcklwd xmm1,xmm5 ; xmm1=BOL
punpckhwd xmm6,xmm5 ; xmm6=BOH
psrld xmm1,1 ; xmm1=BOL*FIX(0.500)
psrld xmm6,1 ; xmm6=BOH*FIX(0.500)
movdqa xmm5,[rel PD_ONEHALFM1_CJ] ; xmm5=[PD_ONEHALFM1_CJ]
paddd xmm7,xmm1
paddd xmm4,xmm6
paddd xmm7,xmm5
paddd xmm4,xmm5
psrld xmm7,SCALEBITS ; xmm7=CbOL
psrld xmm4,SCALEBITS ; xmm4=CbOH
packssdw xmm7,xmm4 ; xmm7=CbO
movdqa xmm1, XMMWORD [wk(2)] ; xmm1=BE
movdqa xmm6,xmm0
punpcklwd xmm0,xmm2
punpckhwd xmm6,xmm2
movdqa xmm5,xmm0
movdqa xmm4,xmm6
pmaddwd xmm0,[rel PW_F0299_F0337] ; xmm0=REL*FIX(0.299)+GEL*FIX(0.337)
pmaddwd xmm6,[rel PW_F0299_F0337] ; xmm6=REH*FIX(0.299)+GEH*FIX(0.337)
pmaddwd xmm5,[rel PW_MF016_MF033] ; xmm5=REL*-FIX(0.168)+GEL*-FIX(0.331)
pmaddwd xmm4,[rel PW_MF016_MF033] ; xmm4=REH*-FIX(0.168)+GEH*-FIX(0.331)
movdqa XMMWORD [wk(6)], xmm0 ; wk(6)=REL*FIX(0.299)+GEL*FIX(0.337)
movdqa XMMWORD [wk(7)], xmm6 ; wk(7)=REH*FIX(0.299)+GEH*FIX(0.337)
pxor xmm0,xmm0
pxor xmm6,xmm6
punpcklwd xmm0,xmm1 ; xmm0=BEL
punpckhwd xmm6,xmm1 ; xmm6=BEH
psrld xmm0,1 ; xmm0=BEL*FIX(0.500)
psrld xmm6,1 ; xmm6=BEH*FIX(0.500)
movdqa xmm1,[rel PD_ONEHALFM1_CJ] ; xmm1=[PD_ONEHALFM1_CJ]
paddd xmm5,xmm0
paddd xmm4,xmm6
paddd xmm5,xmm1
paddd xmm4,xmm1
psrld xmm5,SCALEBITS ; xmm5=CbEL
psrld xmm4,SCALEBITS ; xmm4=CbEH
packssdw xmm5,xmm4 ; xmm5=CbE
psllw xmm7,BYTE_BIT
por xmm5,xmm7 ; xmm5=Cb
movdqa XMMWORD [rbx], xmm5 ; Save Cb
movdqa xmm0, XMMWORD [wk(3)] ; xmm0=BO
movdqa xmm6, XMMWORD [wk(2)] ; xmm6=BE
movdqa xmm1, XMMWORD [wk(1)] ; xmm1=RO
movdqa xmm4,xmm0
punpcklwd xmm0,xmm3
punpckhwd xmm4,xmm3
movdqa xmm7,xmm0
movdqa xmm5,xmm4
pmaddwd xmm0,[rel PW_F0114_F0250] ; xmm0=BOL*FIX(0.114)+GOL*FIX(0.250)
pmaddwd xmm4,[rel PW_F0114_F0250] ; xmm4=BOH*FIX(0.114)+GOH*FIX(0.250)
pmaddwd xmm7,[rel PW_MF008_MF041] ; xmm7=BOL*-FIX(0.081)+GOL*-FIX(0.418)
pmaddwd xmm5,[rel PW_MF008_MF041] ; xmm5=BOH*-FIX(0.081)+GOH*-FIX(0.418)
movdqa xmm3,[rel PD_ONEHALF] ; xmm3=[PD_ONEHALF]
paddd xmm0, XMMWORD [wk(4)]
paddd xmm4, XMMWORD [wk(5)]
paddd xmm0,xmm3
paddd xmm4,xmm3
psrld xmm0,SCALEBITS ; xmm0=YOL
psrld xmm4,SCALEBITS ; xmm4=YOH
packssdw xmm0,xmm4 ; xmm0=YO
pxor xmm3,xmm3
pxor xmm4,xmm4
punpcklwd xmm3,xmm1 ; xmm3=ROL
punpckhwd xmm4,xmm1 ; xmm4=ROH
psrld xmm3,1 ; xmm3=ROL*FIX(0.500)
psrld xmm4,1 ; xmm4=ROH*FIX(0.500)
movdqa xmm1,[rel PD_ONEHALFM1_CJ] ; xmm1=[PD_ONEHALFM1_CJ]
paddd xmm7,xmm3
paddd xmm5,xmm4
paddd xmm7,xmm1
paddd xmm5,xmm1
psrld xmm7,SCALEBITS ; xmm7=CrOL
psrld xmm5,SCALEBITS ; xmm5=CrOH
packssdw xmm7,xmm5 ; xmm7=CrO
movdqa xmm3, XMMWORD [wk(0)] ; xmm3=RE
movdqa xmm4,xmm6
punpcklwd xmm6,xmm2
punpckhwd xmm4,xmm2
movdqa xmm1,xmm6
movdqa xmm5,xmm4
pmaddwd xmm6,[rel PW_F0114_F0250] ; xmm6=BEL*FIX(0.114)+GEL*FIX(0.250)
pmaddwd xmm4,[rel PW_F0114_F0250] ; xmm4=BEH*FIX(0.114)+GEH*FIX(0.250)
pmaddwd xmm1,[rel PW_MF008_MF041] ; xmm1=BEL*-FIX(0.081)+GEL*-FIX(0.418)
pmaddwd xmm5,[rel PW_MF008_MF041] ; xmm5=BEH*-FIX(0.081)+GEH*-FIX(0.418)
movdqa xmm2,[rel PD_ONEHALF] ; xmm2=[PD_ONEHALF]
paddd xmm6, XMMWORD [wk(6)]
paddd xmm4, XMMWORD [wk(7)]
paddd xmm6,xmm2
paddd xmm4,xmm2
psrld xmm6,SCALEBITS ; xmm6=YEL
psrld xmm4,SCALEBITS ; xmm4=YEH
packssdw xmm6,xmm4 ; xmm6=YE
psllw xmm0,BYTE_BIT
por xmm6,xmm0 ; xmm6=Y
movdqa XMMWORD [rdi], xmm6 ; Save Y
pxor xmm2,xmm2
pxor xmm4,xmm4
punpcklwd xmm2,xmm3 ; xmm2=REL
punpckhwd xmm4,xmm3 ; xmm4=REH
psrld xmm2,1 ; xmm2=REL*FIX(0.500)
psrld xmm4,1 ; xmm4=REH*FIX(0.500)
movdqa xmm0,[rel PD_ONEHALFM1_CJ] ; xmm0=[PD_ONEHALFM1_CJ]
paddd xmm1,xmm2
paddd xmm5,xmm4
paddd xmm1,xmm0
paddd xmm5,xmm0
psrld xmm1,SCALEBITS ; xmm1=CrEL
psrld xmm5,SCALEBITS ; xmm5=CrEH
packssdw xmm1,xmm5 ; xmm1=CrE
psllw xmm7,BYTE_BIT
por xmm1,xmm7 ; xmm1=Cr
movdqa XMMWORD [rdx], xmm1 ; Save Cr
sub rcx, byte SIZEOF_XMMWORD
add rsi, byte RGB_PIXELSIZE*SIZEOF_XMMWORD ; inptr
add rdi, byte SIZEOF_XMMWORD ; outptr0
add rbx, byte SIZEOF_XMMWORD ; outptr1
add rdx, byte SIZEOF_XMMWORD ; outptr2
cmp rcx, byte SIZEOF_XMMWORD
jae near .columnloop
test rcx,rcx
jnz near .column_ld1
pop rcx ; col
pop rsi
pop rdi
pop rbx
pop rdx
add rsi, byte SIZEOF_JSAMPROW ; input_buf
add rdi, byte SIZEOF_JSAMPROW
add rbx, byte SIZEOF_JSAMPROW
add rdx, byte SIZEOF_JSAMPROW
dec rax ; num_rows
jg near .rowloop
.return:
pop rbx
uncollect_args
mov rsp,rbp ; rsp <- aligned rbp
pop rsp ; rsp <- original rbp
pop rbp
ret
; For some reason, the OS X linker does not honor the request to align the
; segment unless we do this.
align 16