David Hendricks (dhendrix@chromium.org) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/2606
-gerrit
commit d433f3ca0b710dd092da566c8ffcb963efc30eea Author: David Hendricks dhendrix@chromium.org Date: Wed Mar 6 20:43:55 2013 -0800
Eliminate do_div().
This eliminates the use of do_div() in favor of using libgcc wrapper functions.
This was tested by building and booting on Google Snow (ARMv7) and Qemu (x86). printk()s which use division in vtxprintf() look good.
Change-Id: Icad001d84a3c05bfbf77098f3d644816280b4a4d Signed-off-by: Gabe Black gabeblack@chromium.org Signed-off-by: David Hendricks dhendrix@chromium.org --- src/arch/armv7/Makefile.inc | 2 +- src/arch/armv7/include/div64.h | 233 ---------------------------------------- src/arch/armv7/lib/Makefile.inc | 2 - src/console/vtxprintf.c | 28 ++--- 4 files changed, 15 insertions(+), 250 deletions(-)
diff --git a/src/arch/armv7/Makefile.inc b/src/arch/armv7/Makefile.inc index 0595ae2..8f9915f 100644 --- a/src/arch/armv7/Makefile.inc +++ b/src/arch/armv7/Makefile.inc @@ -124,7 +124,7 @@ endif $(objgenerated)/coreboot_ram.o: $(stages_o) $$(ramstage-objs) $(LIBGCC_FILE_NAME) @printf " CC $(subst $(obj)/,,$(@))\n" ifeq ($(CONFIG_COMPILER_LLVM_CLANG),y) - $(LD) -m -m armelf_linux_eabi -r -o $@ --wrap __divdi3 --wrap __udivdi3 --wrap __moddi3 --wrap __umoddi3 --wrap __uidiv --wrap __do_div64 --start-group $(ramstage-objs) $(LIBGCC_FILE_NAME) --end-group + $(LD) -m -m armelf_linux_eabi -r -o $@ --wrap __divdi3 --wrap __udivdi3 --wrap __moddi3 --wrap __umoddi3 --wrap __uidiv --start-group $(ramstage-objs) $(LIBGCC_FILE_NAME) --end-group else $(CC) $(CFLAGS) -nostdlib -r -o $@ -Wl,--start-group $(stages_o) $(ramstage-objs) $(LIBGCC_FILE_NAME) -Wl,--end-group endif diff --git a/src/arch/armv7/include/div64.h b/src/arch/armv7/include/div64.h deleted file mode 100644 index 5baed2b..0000000 --- a/src/arch/armv7/include/div64.h +++ /dev/null @@ -1,233 +0,0 @@ -/* taken from linux 2.6.31.14 */ - -#ifndef __ASM_ARM_DIV64 -#define __ASM_ARM_DIV64 - -//#include <asm/system.h> -//#include <linux/types.h> -// FIXME - -#define __asmeq(x, y) ".ifnc " x "," y " ; .err ; .endif\n\t" -#define __LINUX_ARM_ARCH__ 7 - -/* - * The semantics of do_div() are: - * - * uint32_t do_div(uint64_t *n, uint32_t base) - * { - * uint32_t remainder = *n % base; - * *n = *n / base; - * return remainder; - * } - * - * In other words, a 64-bit dividend with a 32-bit divisor producing - * a 64-bit result and a 32-bit remainder. To accomplish this optimally - * we call a special __do_div64 helper with completely non standard - * calling convention for arguments and results (beware). - */ - -#ifdef __ARMEB__ -#define __xh "r0" -#define __xl "r1" -#else -#define __xl "r0" -#define __xh "r1" -#endif - -#define __do_div_asm(n, base) \ -({ \ - register unsigned int __base asm("r4") = base; \ - register unsigned long long __n asm("r0") = n; \ - register unsigned long long __res asm("r2"); \ - register unsigned int __rem asm(__xh); \ - asm( __asmeq("%0", __xh) \ - __asmeq("%1", "r2") \ - __asmeq("%2", "r0") \ - __asmeq("%3", "r4") \ - "bl __do_div64" \ - : "=r" (__rem), "=r" (__res) \ - : "r" (__n), "r" (__base) \ - : "ip", "lr", "cc"); \ - n = __res; \ - __rem; \ -}) - -#if __GNUC__ < 4 - -/* - * gcc versions earlier than 4.0 are simply too problematic for the - * optimized implementation below. First there is gcc PR 15089 that - * tend to trig on more complex constructs, spurious .global __udivsi3 - * are inserted even if none of those symbols are referenced in the - * generated code, and those gcc versions are not able to do constant - * propagation on long long values anyway. - */ -#define do_div(n, base) __do_div_asm(n, base) - -#elif __GNUC__ >= 4 - -//#include <asm/bug.h> - -/* - * If the divisor happens to be constant, we determine the appropriate - * inverse at compile time to turn the division into a few inline - * multiplications instead which is much faster. And yet only if compiling - * for ARMv4 or higher (we need umull/umlal) and if the gcc version is - * sufficiently recent to perform proper long long constant propagation. - * (It is unfortunate that gcc doesn't perform all this internally.) - */ -#define do_div(n, base) \ -({ \ - unsigned int __r, __b = (base); \ - if (!__builtin_constant_p(__b) || __b == 0 || \ - (__LINUX_ARM_ARCH__ < 4 && (__b & (__b - 1)) != 0)) { \ - /* non-constant divisor (or zero): slow path */ \ - __r = __do_div_asm(n, __b); \ - } else if ((__b & (__b - 1)) == 0) { \ - /* Trivial: __b is constant and a power of 2 */ \ - /* gcc does the right thing with this code. */ \ - __r = n; \ - __r &= (__b - 1); \ - n /= __b; \ - } else { \ - /* Multiply by inverse of __b: n/b = n*(p/b)/p */ \ - /* We rely on the fact that most of this code gets */ \ - /* optimized away at compile time due to constant */ \ - /* propagation and only a couple inline assembly */ \ - /* instructions should remain. Better avoid any */ \ - /* code construct that might prevent that. */ \ - unsigned long long __res, __x, __t, __m, __n = n; \ - unsigned int __c, __p, __z = 0; \ - /* preserve low part of n for reminder computation */ \ - __r = __n; \ - /* determine number of bits to represent __b */ \ - __p = 1 << __div64_fls(__b); \ - /* compute __m = ((__p << 64) + __b - 1) / __b */ \ - __m = (~0ULL / __b) * __p; \ - __m += (((~0ULL % __b + 1) * __p) + __b - 1) / __b; \ - /* compute __res = __m*(~0ULL/__b*__b-1)/(__p << 64) */ \ - __x = ~0ULL / __b * __b - 1; \ - __res = (__m & 0xffffffff) * (__x & 0xffffffff); \ - __res >>= 32; \ - __res += (__m & 0xffffffff) * (__x >> 32); \ - __t = __res; \ - __res += (__x & 0xffffffff) * (__m >> 32); \ - __t = (__res < __t) ? (1ULL << 32) : 0; \ - __res = (__res >> 32) + __t; \ - __res += (__m >> 32) * (__x >> 32); \ - __res /= __p; \ - /* Now sanitize and optimize what we've got. */ \ - if (~0ULL % (__b / (__b & -__b)) == 0) { \ - /* those cases can be simplified with: */ \ - __n /= (__b & -__b); \ - __m = ~0ULL / (__b / (__b & -__b)); \ - __p = 1; \ - __c = 1; \ - } else if (__res != __x / __b) { \ - /* We can't get away without a correction */ \ - /* to compensate for bit truncation errors. */ \ - /* To avoid it we'd need an additional bit */ \ - /* to represent __m which would overflow it. */ \ - /* Instead we do m=p/b and n/b=(n*m+m)/p. */ \ - __c = 1; \ - /* Compute __m = (__p << 64) / __b */ \ - __m = (~0ULL / __b) * __p; \ - __m += ((~0ULL % __b + 1) * __p) / __b; \ - } else { \ - /* Reduce __m/__p, and try to clear bit 31 */ \ - /* of __m when possible otherwise that'll */ \ - /* need extra overflow handling later. */ \ - unsigned int __bits = -(__m & -__m); \ - __bits |= __m >> 32; \ - __bits = (~__bits) << 1; \ - /* If __bits == 0 then setting bit 31 is */ \ - /* unavoidable. Simply apply the maximum */ \ - /* possible reduction in that case. */ \ - /* Otherwise the MSB of __bits indicates the */ \ - /* best reduction we should apply. */ \ - if (!__bits) { \ - __p /= (__m & -__m); \ - __m /= (__m & -__m); \ - } else { \ - __p >>= __div64_fls(__bits); \ - __m >>= __div64_fls(__bits); \ - } \ - /* No correction needed. */ \ - __c = 0; \ - } \ - /* Now we have a combination of 2 conditions: */ \ - /* 1) whether or not we need a correction (__c), and */ \ - /* 2) whether or not there might be an overflow in */ \ - /* the cross product (__m & ((1<<63) | (1<<31))) */ \ - /* Select the best insn combination to perform the */ \ - /* actual __m * __n / (__p << 64) operation. */ \ - if (!__c) { \ - asm ( "umull %Q0, %R0, %1, %Q2\n\t" \ - "mov %Q0, #0" \ - : "=&r" (__res) \ - : "r" (__m), "r" (__n) \ - : "cc" ); \ - } else if (!(__m & ((1ULL << 63) | (1ULL << 31)))) { \ - __res = __m; \ - asm ( "umlal %Q0, %R0, %Q1, %Q2\n\t" \ - "mov %Q0, #0" \ - : "+&r" (__res) \ - : "r" (__m), "r" (__n) \ - : "cc" ); \ - } else { \ - asm ( "umull %Q0, %R0, %Q1, %Q2\n\t" \ - "cmn %Q0, %Q1\n\t" \ - "adcs %R0, %R0, %R1\n\t" \ - "adc %Q0, %3, #0" \ - : "=&r" (__res) \ - : "r" (__m), "r" (__n), "r" (__z) \ - : "cc" ); \ - } \ - if (!(__m & ((1ULL << 63) | (1ULL << 31)))) { \ - asm ( "umlal %R0, %Q0, %R1, %Q2\n\t" \ - "umlal %R0, %Q0, %Q1, %R2\n\t" \ - "mov %R0, #0\n\t" \ - "umlal %Q0, %R0, %R1, %R2" \ - : "+&r" (__res) \ - : "r" (__m), "r" (__n) \ - : "cc" ); \ - } else { \ - asm ( "umlal %R0, %Q0, %R2, %Q3\n\t" \ - "umlal %R0, %1, %Q2, %R3\n\t" \ - "mov %R0, #0\n\t" \ - "adds %Q0, %1, %Q0\n\t" \ - "adc %R0, %R0, #0\n\t" \ - "umlal %Q0, %R0, %R2, %R3" \ - : "+&r" (__res), "+&r" (__z) \ - : "r" (__m), "r" (__n) \ - : "cc" ); \ - } \ - __res /= __p; \ - /* The reminder can be computed with 32-bit regs */ \ - /* only, and gcc is good at that. */ \ - { \ - unsigned int __res0 = __res; \ - unsigned int __b0 = __b; \ - __r -= __res0 * __b0; \ - } \ - /* BUG_ON(__r >= __b || __res * __b + __r != n); */ \ - n = __res; \ - } \ - __r; \ -}) - -/* our own fls implementation to make sure constant propagation is fine */ -#define __div64_fls(bits) \ -({ \ - unsigned int __left = (bits), __nr = 0; \ - if (__left & 0xffff0000) __nr += 16, __left >>= 16; \ - if (__left & 0x0000ff00) __nr += 8, __left >>= 8; \ - if (__left & 0x000000f0) __nr += 4, __left >>= 4; \ - if (__left & 0x0000000c) __nr += 2, __left >>= 2; \ - if (__left & 0x00000002) __nr += 1; \ - __nr; \ -}) - -#endif - -#endif diff --git a/src/arch/armv7/lib/Makefile.inc b/src/arch/armv7/lib/Makefile.inc index 388864a..508f776 100644 --- a/src/arch/armv7/lib/Makefile.inc +++ b/src/arch/armv7/lib/Makefile.inc @@ -6,12 +6,10 @@ bootblock-y += cache-cp15.c romstage-y += cache_v7.c romstage-y += cache-cp15.c romstage-y += div0.c -romstage-y += div64.S romstage-y += syslib.c romstage-$(CONFIG_EARLY_CONSOLE) += early_console.c
ramstage-y += div0.c -ramstage-y += div64.S #ramstage-y += interrupts.c #ramstage-y += memcpy.S #ramstage-y += memset.S diff --git a/src/console/vtxprintf.c b/src/console/vtxprintf.c index 9de2584..0146805 100644 --- a/src/console/vtxprintf.c +++ b/src/console/vtxprintf.c @@ -5,7 +5,6 @@ */
#include <string.h> -#include <div64.h> #include <console/console.h> #include <console/vtxprintf.h>
@@ -70,20 +69,21 @@ static int number(void (*tx_byte)(unsigned char byte), if (num == 0) tmp[i++]='0'; else while (num != 0){ - /* there are some nice optimizations in the - * Macros-From-Hell that form the div64 code - * *IF* you call it with a constant. - * We're firmware, we only do bases - * 8, 10, and 16. Let's be smart. - * This greatly helps ARM, reduces the - * code footprint at compile time, and does not hurt x86. + /* + * We're firmware, we only do bases 8, 10, and 16. Let's be + * smart. This greatly helps ARM, reduces the code footprint + * at compile time, and does not hurt x86. */ - if (base == 10) - tmp[i++] = digits[do_div(num,10)]; - else if (base == 8) - tmp[i++] = digits[do_div(num,8)]; - else /* sorry, you're out of choices */ - tmp[i++] = digits[do_div(num,16)]; + if (base == 10) { + tmp[i++] = digits[num % 10]; + num /= 10; + } else if (base == 8) { + tmp[i++] = digits[num % 8]; + num /= 8; + } else { /* sorry, you're out of choices */ + tmp[i++] = digits[num % 16]; + num /= 16; + } } if (i > precision) precision = i;
-
David Hendricks