[coreboot] Patch set updated for coreboot: d433f3c Eliminate do_div().
David Hendricks (dhendrix@chromium.org)
gerrit at coreboot.org
Thu Mar 7 21:03:57 CET 2013
David Hendricks (dhendrix at 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 at 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 at chromium.org>
Signed-off-by: David Hendricks <dhendrix at 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;
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