Made ROM padding code ~42% faster.

Author: profi200

include/arm11/fast_rom_padding.h

@@ -0,0 +1,34 @@
+#pragma once
+
+/*
+ *   This file is part of open_agb_firm
+ *   Copyright (C) 2024 profi200
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "types.h"
+
+
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+void makeOpenBusPaddingFast(u32 *romEnd);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif

source/arm11/fast_rom_padding.s

@@ -0,0 +1,60 @@
+@ This file is part of open_agb_firm
+@ Copyright (C) 2024 profi200
+@
+@ This program is free software: you can redistribute it and/or modify
+@ it under the terms of the GNU General Public License as published by
+@ the Free Software Foundation, either version 3 of the License, or
+@ (at your option) any later version.
+@
+@ This program is distributed in the hope that it will be useful,
+@ but WITHOUT ANY WARRANTY; without even the implied warranty of
+@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+@ GNU General Public License for more details.
+@
+@ You should have received a copy of the GNU General Public License
+@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include "asm_macros.h"
+
+.syntax unified
+.cpu mpcore
+.fpu vfpv2
+
+
+
+@ void makeOpenBusPaddingFast(u32 *romEnd);
+BEGIN_ASM_FUNC makeOpenBusPaddingFast
+	@ Save registers and calculate size from start and highest ROM address.
+	stmfd sp!, {r4, lr}                   @ Save registers.
+	rsb  r1,  r0, #0x22000000             @ r1 = 0x22000000 - r0;
+
+	@ Generate pattern halves from address.
+	lsr  r2,  r0, #1                      @ r2 = r0>>1;
+	add  r3,  r2, #1                      @ r3 = r2 + 1;
+
+	@ Generate constant for incrementing the pattern halves.
+	mov r12, #2                           @ r12 = 2;
+	add r12, r12, #0x20000                @ r12 += 0x20000;
+
+	@ Join pattern halves and precalculate the next 3 patterns.
+	pkhbt  r2,  r2,  r3, lsl #16          @ r2 = (r2 & 0xFFFF) | r3<<16;
+	uadd16  r3,  r2, r12                  @ r3 = ((r2 + 0x20000) & 0xFFFF0000) | ((r2 + 2) & 0xFFFF); // r12 is 0x20002.
+	uadd16  r4,  r3, r12                  @ r4 = ((r3 + 0x20000) & 0xFFFF0000) | ((r3 + 2) & 0xFFFF); // r12 is 0x20002.
+	uadd16  lr,  r4, r12                  @ lr = ((r4 + 0x20000) & 0xFFFF0000) | ((r4 + 2) & 0xFFFF); // r12 is 0x20002.
+
+	@ Adjust constant for unrolled loop. 0x20002 --> 0x80008.
+	lsl r12, r12, #2                      @ r12 <<= 2;
+	makeOpenBusPaddingFast_blk_lp:
+		@ Store 16 pattern bytes at a time and decrement size.
+		stmia r0!, {r2-r4, lr}            @ *((_16BytesBlock*)r0) = r2_to_r4_lr; r0 += 16;
+		subs  r1,  r1, #16                @ r1 -= 16; // Updates flags.
+
+		@ Increment patterns and jump back if we are not done yet.
+		uadd16  r2,  r2, r12              @ r2 = ((r2 + 0x80000) & 0xFFFF0000) | ((r2 + 8) & 0xFFFF); // r12 is 0x80008.
+		uadd16  r3,  r3, r12              @ r3 = ((r3 + 0x80000) & 0xFFFF0000) | ((r3 + 8) & 0xFFFF); // r12 is 0x80008.
+		uadd16  r4,  r4, r12              @ r3 = ((r4 + 0x80000) & 0xFFFF0000) | ((r4 + 8) & 0xFFFF); // r12 is 0x80008.
+		uadd16  lr,  lr, r12              @ lr = ((lr + 0x80000) & 0xFFFF0000) | ((lr + 8) & 0xFFFF); // r12 is 0x80008.
+		bne makeOpenBusPaddingFast_blk_lp @ if(r1 != 0) goto makeOpenBusPaddingFast_blk_lp;
+
+	ldmfd sp!, {r4, pc}                   @ Restore registers and return.
+END_ASM_FUNC

source/arm11/open_agb_firm.c

@@ -20,7 +20,7 @@
 #include <string.h>
 #include "types.h"
 #include "util.h"
-#include "arm_intrinsic.h"
+#include "arm11/fast_rom_padding.h"
 #include "oaf_error_codes.h"
 #include "fs.h"
 #include "arm11/fmt.h"
@@ -49,9 +49,9 @@ static u32 fixRomPadding(const u32 romFileSize)
 	// Pad unused ROM area with 0xFFs (trimmed ROMs).
 	// Smallest retail ROM chip is 8 Mbit (1 MiB).
 	u32 romSize = nextPow2(romFileSize);
-	if(romSize < 0x100000) romSize = 0x100000;
+	romSize = (romSize < 0x100000 ? 0x100000 : romSize);
 	const uintptr_t romLoc = LGY_ROM_LOC;
-	memset((void*)(romLoc + romFileSize), 0xFFFFFFFF, romSize - romFileSize);
+	memset((void*)(romLoc + romFileSize), 0xFF, romSize - romFileSize);
 
 	u32 mirroredSize = romSize;
 	if(romSize == 0x100000) // 1 MiB.
@@ -69,13 +69,7 @@ static u32 fixRomPadding(const u32 romFileSize)
 	}
 
 	// Fake "open bus" padding.
-	u32 padding = (romLoc + mirroredSize) / 2;
-	padding = __pkhbt(padding, padding + 1, 16); // Copy lower half + 1 to upper half.
-	for(uintptr_t i = romLoc + mirroredSize; i < romLoc + LGY_MAX_ROM_SIZE; i += 4)
-	{
-		*(u32*)i = padding;
-		padding = __uadd16(padding, 0x20002); // Unsigned parallel halfword-wise addition.
-	}
+	makeOpenBusPaddingFast((u32*)(romLoc + mirroredSize));
 
 	// We don't return the mirrored size because the db hashes are over unmirrored dumps.
 	return romSize;