ARM opts in draw_scale.c; updated android build opts.

Kammerer reports 90%+ of CPU time is spent in the image scaling code
for his documents on Android.

In this commit we provide ARM optimised cores for the common scaling
routines (1/2/4 components). Tests indicate this doubles the speed of
rendering for a bitmap heavy PDF file on an HTC desire.

This code is included if ARCH_ARM is defined. If ARCH_THUMB is defined
then extra instructions are added to ensure correct interworking.

We also update the Android jni makefiles to set these defines.

We update the ReadMe.txt with more explicit instructions and update with
more modern ndk/sdk versions.

We update build.xml in line with new sdk releases.

1 files changed, 285 insertions, 83 deletions

diff --git a/draw/draw_scale.c b/draw/draw_scale.c
index 427512ce..bb766398 100644
--- a/draw/draw_scale.c
+++ b/draw/draw_scale.c
@@ -16,6 +16,21 @@ and then positioning it at (frac(x),frac(y)).
  */
 #define SINGLE_PIXEL_SPECIALS
 
+/* If we're compiling as thumb code, then we need to tell the compiler
+ * to enter and exit ARM mode around our assembly sections. If we move
+ * the ARM functions to a separate file and arrange for it to be compiled
+ * without thumb mode, we can save some time on entry.
+ */
+#ifdef ARCH_ARM
+#ifdef ARCH_THUMB
+#define ENTER_ARM   ".balign 4\nmov r12,pc\nbx r12\n0:.arm\n"
+#define ENTER_THUMB "9:.thumb\n"
+#else
+#define ENTER_ARM
+#define ENTER_THUMB
+#endif
+#endif
+
 #ifdef DEBUG_SCALING
 #ifdef WIN32
 #include <windows.h>
@@ -247,10 +262,10 @@ typedef struct fz_weights_s fz_weights;
 
 struct fz_weights_s
 {
+	int flip;
 	int count;
 	int max_len;
 	int n;
-	int flip;
 	int new_line;
 	int index[1];
 };
@@ -584,6 +599,274 @@ scale_row_to_temp(int *dst, unsigned char *src, fz_weights *weights)
 	}
 }
 
+#ifdef ARCH_ARM
+
+static void
+scale_row_to_temp1(int *dst, unsigned char *src, fz_weights *weights)
+__attribute__((naked));
+
+static void
+scale_row_to_temp2(int *dst, unsigned char *src, fz_weights *weights)
+__attribute__((naked));
+
+static void
+scale_row_to_temp4(int *dst, unsigned char *src, fz_weights *weights)
+__attribute__((naked));
+
+static void
+scale_row_from_temp(unsigned char *dst, int *src, fz_weights *weights, int width, int row)
+__attribute__((naked));
+
+static void
+scale_row_to_temp1(int *dst, unsigned char *src, fz_weights *weights)
+{
+	/* possible optimisation in here; unroll inner loops to avoid stall. */
+	asm volatile(
+	ENTER_ARM
+	"stmfd	r13!,{r4-r5,r9,r14}				\n"
+	"@ r0 = dst						\n"
+	"@ r1 = src						\n"
+	"@ r2 = weights						\n"
+	"ldr	r12,[r2],#4		@ r12= flip		\n"
+	"ldr	r3, [r2],#16		@ r3 = count r2 = &index\n"
+	"ldr    r4, [r2]		@ r4 = index[0]		\n"
+	"cmp	r12,#0			@ if (flip)		\n"
+	"beq	4f			@ {			\n"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"add	r0, r0, r3, LSL #2	@ dst += count		\n"
+	"1:							\n"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = a = 0		\n"
+	"add	r4, r1, r4		@ r4 = min = &src[r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	3f			@ {			\n"
+	"2:							\n"
+	"ldr	r12,[r2], #4		@ r12 = *contrib++	\n"
+	"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"@stall on r14						\n"
+	"mla	r5, r12,r14,r5		@ g += r14 * r12	\n"
+	"bgt	2b			@ }			\n"
+	"3:							\n"
+	"str	r5,[r0, #-4]!		@ *--dst=a		\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	1b			@ 			\n"
+	"ldmfd	r13!,{r4-r5,r9,PC}	@ pop, return to thumb	\n"
+	"4:"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"5:"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = a = 0		\n"
+	"add	r4, r1, r4		@ r4 = min = &src[r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	7f			@ {			\n"
+	"6:							\n"
+	"ldr	r12,[r2], #4		@ r12 = *contrib++	\n"
+	"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"@stall on r14						\n"
+	"mla	r5, r12,r14,r5		@ a += r14 * r12	\n"
+	"bgt	6b			@ }			\n"
+	"7:							\n"
+	"str	r5, [r0], #4		@ *dst++=a		\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	5b			@ 			\n"
+	"ldmfd	r13!,{r4-r5,r9,PC}	@ pop, return to thumb	\n"
+	ENTER_THUMB
+	);
+}
+
+static void
+scale_row_to_temp2(int *dst, unsigned char *src, fz_weights *weights)
+{
+	asm volatile(
+	ENTER_ARM
+	"stmfd	r13!,{r4-r6,r9-r11,r14}				\n"
+	"@ r0 = dst						\n"
+	"@ r1 = src						\n"
+	"@ r2 = weights						\n"
+	"ldr	r12,[r2],#4		@ r12= flip		\n"
+	"ldr	r3, [r2],#16		@ r3 = count r2 = &index\n"
+	"ldr    r4, [r2]		@ r4 = index[0]		\n"
+	"cmp	r12,#0			@ if (flip)		\n"
+	"beq	4f			@ {			\n"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"add	r0, r0, r3, LSL #3	@ dst += 2*count	\n"
+	"1:							\n"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = g = 0		\n"
+	"mov	r6, #0			@ r6 = a = 0		\n"
+	"add	r4, r1, r4, LSL #1	@ r4 = min = &src[2*r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	3f			@ {			\n"
+	"2:							\n"
+	"ldr	r14,[r2], #4		@ r14 = *contrib++	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"mla	r5, r14,r11,r5		@ g += r11 * r14	\n"
+	"mla	r6, r14,r12,r6		@ a += r12 * r14	\n"
+	"bgt	2b			@ }			\n"
+	"3:							\n"
+	"stmdb	r0!,{r5,r6}		@ *--dst=a;*--dst=g;	\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	1b			@ 			\n"
+	"ldmfd	r13!,{r4-r6,r9-r11,PC}	@ pop, return to thumb	\n"
+	"4:"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"5:"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = g = 0		\n"
+	"mov	r6, #0			@ r6 = a = 0		\n"
+	"add	r4, r1, r4, LSL #1	@ r4 = min = &src[2*r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	7f			@ {			\n"
+	"6:							\n"
+	"ldr	r14,[r2], #4		@ r10 = *contrib++	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"mla	r5, r14,r11,r5		@ g += r11 * r14	\n"
+	"mla	r6, r14,r12,r6		@ a += r12 * r14	\n"
+	"bgt	6b			@ }			\n"
+	"7:							\n"
+	"stmia	r0!,{r5,r6}		@ *dst++=r;*dst++=g;	\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	5b			@ 			\n"
+	"ldmfd	r13!,{r4-r6,r9-r11,PC}	@ pop, return to thumb	\n"
+	ENTER_THUMB
+	);
+}
+
+static void
+scale_row_to_temp4(int *dst, unsigned char *src, fz_weights *weights)
+{
+	asm volatile(
+	ENTER_ARM
+	"stmfd	r13!,{r4-r11,r14}				\n"
+	"@ r0 = dst						\n"
+	"@ r1 = src						\n"
+	"@ r2 = weights						\n"
+	"ldr	r12,[r2],#4		@ r12= flip		\n"
+	"ldr	r3, [r2],#16		@ r3 = count r2 = &index\n"
+	"ldr    r4, [r2]		@ r4 = index[0]		\n"
+	"cmp	r12,#0			@ if (flip)		\n"
+	"beq	4f			@ {			\n"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"add	r0, r0, r3, LSL #4	@ dst += 4*count	\n"
+	"1:							\n"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = r = 0		\n"
+	"mov	r6, #0			@ r6 = g = 0		\n"
+	"mov	r7, #0			@ r7 = b = 0		\n"
+	"mov	r8, #0			@ r8 = a = 0		\n"
+	"add	r4, r1, r4, LSL #2	@ r4 = min = &src[4*r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	3f			@ {			\n"
+	"2:							\n"
+	"ldr	r10,[r2], #4		@ r10 = *contrib++	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
+	"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
+	"mla	r5, r10,r11,r5		@ r += r11 * r10	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"mla	r6, r10,r12,r6		@ g += r12 * r10	\n"
+	"mla	r7, r10,r14,r7		@ b += r14 * r10	\n"
+	"mla	r8, r10,r11,r8		@ a += r11 * r10	\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"bgt	2b			@ }			\n"
+	"3:							\n"
+	"stmdb	r0!,{r5,r6,r7,r8}	@ *--dst=a;*--dst=b;	\n"
+	"				@ *--dst=g;*--dst=r;	\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	1b			@ 			\n"
+	"ldmfd	r13!,{r4-r11,PC}	@ pop, return to thumb	\n"
+	"4:"
+	"add	r2, r2, r4, LSL #2	@ r2 = &index[index[0]] \n"
+	"5:"
+	"ldr	r4, [r2], #4		@ r4 = *contrib++	\n"
+	"ldr	r9, [r2], #4		@ r9 = len = *contrib++	\n"
+	"mov	r5, #0			@ r5 = r = 0		\n"
+	"mov	r6, #0			@ r6 = g = 0		\n"
+	"mov	r7, #0			@ r7 = b = 0		\n"
+	"mov	r8, #0			@ r8 = a = 0		\n"
+	"add	r4, r1, r4, LSL #2	@ r4 = min = &src[4*r4]	\n"
+	"cmp	r9, #0			@ while (len-- > 0)	\n"
+	"beq	7f			@ {			\n"
+	"6:							\n"
+	"ldr	r10,[r2], #4		@ r10 = *contrib++	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
+	"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
+	"mla	r5, r10,r11,r5		@ r += r11 * r10	\n"
+	"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
+	"mla	r6, r10,r12,r6		@ g += r12 * r10	\n"
+	"mla	r7, r10,r14,r7		@ b += r14 * r10	\n"
+	"mla	r8, r10,r11,r8		@ a += r11 * r10	\n"
+	"subs	r9, r9, #1		@ r9 = len--		\n"
+	"bgt	6b			@ }			\n"
+	"7:							\n"
+	"stmia	r0!,{r5,r6,r7,r8}	@ *dst++=r;*dst++=g;	\n"
+	"				@ *dst++=b;*dst++=a;	\n"
+	"subs	r3, r3, #1		@ i--			\n"
+	"bgt	5b			@ 			\n"
+	"ldmfd	r13!,{r4-r11,PC}	@ pop, return to thumb	\n"
+	ENTER_THUMB
+	);
+}
+
+static void
+scale_row_from_temp(unsigned char *dst, int *src, fz_weights *weights, int width, int row)
+{
+	asm volatile(
+	ENTER_ARM
+	"ldr	r12,[r13]		@ r12= row		\n"
+	"add	r2, r2, #20		@ r2 = weights->index	\n"
+	"stmfd	r13!,{r4-r11,r14}				\n"
+	"@ r0 = dst						\n"
+	"@ r1 = src						\n"
+	"@ r2 = &weights->index[0]				\n"
+	"@ r3 = width						\n"
+	"@ r12= row						\n"
+	"ldr    r4, [r2, r12, LSL #2]	@ r4 = index[row]	\n"
+	"add	r2, r2, #4		@ r2 = &index[1]	\n"
+	"mov	r6, r3			@ r6 = x = width	\n"
+	"ldr	r14,[r2, r4, LSL #2]!	@ r2 = contrib = index[index[row]+1]\n"
+	"				@ r14= len = *contrib	\n"
+	"1:							\n"
+	"mov	r5, r1			@ r5 = min = src	\n"
+	"mov	r7, #1<<15		@ r7 = val = 1<<15	\n"
+	"movs	r8, r14			@ r8 = len2 = len	\n"
+	"add	r9, r2, #4		@ r9 = contrib2		\n"
+	"ble	3f			@ while (len2-- > 0) {	\n"
+	"2:							\n"
+	"ldr	r10,[r9], #4		@ r10 = *contrib2++	\n"
+	"ldr	r12,[r5], r3, LSL #2	@ r12 = *min	r5 = min += width\n"
+	"subs	r8, r8, #1		@ len2--		\n"
+	"@ stall r12						\n"
+	"mla	r7, r10,r12,r7		@ val += r12 * r10	\n"
+	"bgt	2b			@ }			\n"
+	"3:							\n"
+	"movs	r7, r7, asr #16		@ r7 = val >>= 16	\n"
+	"movlt	r7, #0			@ if (r7 < 0) r7 = 0	\n"
+	"cmp	r7, #255		@ if (r7 > 255)		\n"
+	"add	r1, r1, #4		@ src++			\n"
+	"movgt	r7, #255		@     r7 = 255		\n"
+	"subs	r6, r6, #1		@ x--			\n"
+	"strb	r7, [r0], #1		@ *dst++ = val		\n"
+	"bgt	1b			@ 			\n"
+	"ldmfd	r13!,{r4-r11,PC}	@ pop, return to thumb	\n"
+	ENTER_THUMB
+	);
+}
+
+#else
+
 static void
 scale_row_to_temp1(int *dst, unsigned char *src, fz_weights *weights)
 {
@@ -672,54 +955,13 @@ static void
 scale_row_to_temp4(int *dst, unsigned char *src, fz_weights *weights)
 {
 	int *contrib = &weights->index[weights->index[0]];
-#ifndef ARCH_ARM
 	int len, i;
 	unsigned char *min;
-#endif
 
 	assert(weights->n == 4);
 	if (weights->flip)
 	{
 		dst += 4*weights->count;
-#ifdef ARCH_ARM
-		asm volatile(
-		"1:"
-		"ldr	r4, [%2], #4		@ r4 = *contrib++	\n"
-		"ldr	r9, [%2], #4		@ r9 = len = *contrib++	\n"
-		"mov	r5, #0			@ r5 = r = 0		\n"
-		"mov	r6, #0			@ r6 = g = 0		\n"
-		"mov	r7, #0			@ r7 = b = 0		\n"
-		"mov	r8, #0			@ r8 = a = 0		\n"
-		"add	r4, %1, r4, LSL #2	@ r4 = min = &src[4*r4]	\n"
-		"cmp	r9, #0			@ while (len-- > 0)	\n"
-		"beq	3f			@ {			\n"
-		"2:							\n"
-		"ldr	r10,[%2], #4		@ r10 = *contrib++	\n"
-		"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
-		"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
-		"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
-		"mla	r5, r10,r11,r5		@ r += r11 * r10	\n"
-		"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
-		"mla	r6, r10,r12,r6		@ g += r12 * r10	\n"
-		"mla	r7, r10,r14,r7		@ b += r14 * r10	\n"
-		"mla	r8, r10,r11,r8		@ a += r11 * r10	\n"
-		"subs	r9, r9, #1		@ r9 = len--		\n"
-		"bgt	2b			@ }			\n"
-		"stmdb	%0!,{r5,r6,r7,r8}	@ *--dst=a;*--dst=b;	\n"
-		"3:				@ *--dst=g;*--dst=r;	\n"
-		"subs	%3, %3, #1		@ i--			\n"
-		"bgt	1b			@ 			\n"
-		:
-		:
-		"r" (dst),
-		"r" (src),
-		"r" (contrib),
-		"r" (weights->count)
-		:
-		"r4","r5","r6","r7","r8","r9","r10","r11","r12","r14",
-		"memory","cc"
-		);
-#else
 		for (i=weights->count; i > 0; i--)
 		{
 			int r = 0;
@@ -740,49 +982,9 @@ scale_row_to_temp4(int *dst, unsigned char *src, fz_weights *weights)
 			*--dst = g;
 			*--dst = r;
 		}
-#endif
 	}
 	else
 	{
-#ifdef ARCH_ARM
-		asm volatile(
-		"1:"
-		"ldr	r4, [%2], #4		@ r4 = *contrib++	\n"
-		"ldr	r9, [%2], #4		@ r9 = len = *contrib++	\n"
-		"mov	r5, #0			@ r5 = r = 0		\n"
-		"mov	r6, #0			@ r6 = g = 0		\n"
-		"mov	r7, #0			@ r7 = b = 0		\n"
-		"mov	r8, #0			@ r8 = a = 0		\n"
-		"add	r4, %1, r4, LSL #2	@ r4 = min = &src[4*r4]	\n"
-		"cmp	r9, #0			@ while (len-- > 0)	\n"
-		"beq	3f			@ {			\n"
-		"2:							\n"
-		"ldr	r10,[%2], #4		@ r10 = *contrib++	\n"
-		"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
-		"ldrb	r12,[r4], #1		@ r12 = *min++		\n"
-		"ldrb	r14,[r4], #1		@ r14 = *min++		\n"
-		"mla	r5, r10,r11,r5		@ r += r11 * r10	\n"
-		"ldrb	r11,[r4], #1		@ r11 = *min++		\n"
-		"mla	r6, r10,r12,r6		@ g += r12 * r10	\n"
-		"mla	r7, r10,r14,r7		@ b += r14 * r10	\n"
-		"mla	r8, r10,r11,r8		@ a += r11 * r10	\n"
-		"subs	r9, r9, #1		@ r9 = len--		\n"
-		"bgt	2b			@ }			\n"
-		"stmia	%0!,{r5,r6,r7,r8}	@ *dst++=r;*dst++=g;	\n"
-		"3:				@ *dst++=b;*dst++=a;	\n"
-		"subs	%3, %3, #1		@ i--			\n"
-		"bgt	1b			@ 			\n"
-		:
-		:
-		"r" (dst),
-		"r" (src),
-		"r" (contrib),
-		"r" (weights->count)
-		:
-		"r4","r5","r6","r7","r8","r9","r10","r11","r12","r14",
-		"memory","cc"
-		);
-#else
 		for (i=weights->count; i > 0; i--)
 		{
 			int r = 0;
@@ -803,7 +1005,6 @@ scale_row_to_temp4(int *dst, unsigned char *src, fz_weights *weights)
 			*dst++ = b;
 			*dst++ = a;
 		}
-#endif
 	}
 }
 
@@ -836,6 +1037,7 @@ scale_row_from_temp(unsigned char *dst, int *src, fz_weights *weights, int width
 		src++;
 	}
 }
+#endif
 
 #ifdef SINGLE_PIXEL_SPECIALS
 static void