Re: [PATCH v2] powerpc/math-emu: Update macros from gmp-6.1.2
From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2018-11-19 18:56:36
On Tue, Nov 13, 2018 at 6:44 PM Joel Stanley [off-list ref] wrote:
The add_ssaaaa, sub_ddmmss, umul_ppmm and udiv_qrnnd macros originate
from GMP's longlong.h.
This was found when compiling with clang:
arch/powerpc/math-emu/fnmsub.c:46:2: error: invalid use of a cast in a
inline asm context requiring an l-value: remove the cast or build with
-fheinous-gnu-extensions
FP_ADD_D(R, T, B);
^~~~~~~~~~~~~~~~~
...
./arch/powerpc/include/asm/sfp-machine.h:283:27: note: expanded from
macro 'sub_ddmmss'
: "=r" ((USItype)(sh)), \
~~~~~~~~~~^~~
Segher points out: this was fixed in GCC over 16 years ago
( https://gcc.gnu.org/r56600 ), and in GMP (where it comes from)
presumably before that.
Update to the latest version in order to git rid of the invalid casts.Hi Joel, thanks for this patch. It's a much better fix IMO than v1. One nit below.
The only functional change I noticed was this in udiv_qrnnd.
__r1 = (n1) % __d1;
__q1 = (n1) / __d1;
Becomes this:
__q1 = (n1) / __d1;
__r1 = (n1) - __q1 * __d1;
This is equivalent as it instead of calculating the remainder
using modulo, it uses the result of integer division to subtract the
count of 'whole' d1 from r1.I don't understand this; why was this functional change made?
quoted hunk ↗ jump to hunk
Link: https://github.com/ClangBuiltLinux/linux/issues/260 Signed-off-by: Joel Stanley <joel@jms.id.au> --- v1: https://lore.kernel.org/linuxppc-dev/20181102033713.31916-1-joel@jms.id.au/ (local) v2: Instead of setting the -fheinous-gnu-extensions for clang, fix the code. arch/powerpc/include/asm/sfp-machine.h | 99 +++++++++----------------- 1 file changed, 32 insertions(+), 67 deletions(-)diff --git a/arch/powerpc/include/asm/sfp-machine.h b/arch/powerpc/include/asm/sfp-machine.h index d89beaba26ff..a6353d9dd5ba 100644 --- a/arch/powerpc/include/asm/sfp-machine.h +++ b/arch/powerpc/include/asm/sfp-machine.h@@ -213,30 +213,18 @@ * respectively. The result is placed in HIGH_SUM and LOW_SUM. Overflow * (i.e. carry out) is not stored anywhere, and is lost. */ -#define add_ssaaaa(sh, sl, ah, al, bh, bl) \ +#define add_ssaaaa(sh, sl, ah, al, bh, bl) \ do { \ if (__builtin_constant_p (bh) && (bh) == 0) \ - __asm__ ("{a%I4|add%I4c} %1,%3,%4\n\t{aze|addze} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "%r" ((USItype)(ah)), \ - "%r" ((USItype)(al)), \ - "rI" ((USItype)(bl))); \ - else if (__builtin_constant_p (bh) && (bh) ==~(USItype) 0) \ - __asm__ ("{a%I4|add%I4c} %1,%3,%4\n\t{ame|addme} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "%r" ((USItype)(ah)), \ - "%r" ((USItype)(al)), \ - "rI" ((USItype)(bl))); \ + __asm__ ("add%I4c %1,%3,%4\n\taddze %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (ah), "%r" (al), "rI" (bl)); \ + else if (__builtin_constant_p (bh) && (bh) == ~(USItype) 0) \ + __asm__ ("add%I4c %1,%3,%4\n\taddme %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (ah), "%r" (al), "rI" (bl)); \ else \ - __asm__ ("{a%I5|add%I5c} %1,%4,%5\n\t{ae|adde} %0,%2,%3" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "%r" ((USItype)(ah)), \ - "r" ((USItype)(bh)), \ - "%r" ((USItype)(al)), \ - "rI" ((USItype)(bl))); \ + __asm__ ("add%I5c %1,%4,%5\n\tadde %0,%2,%3" \ + : "=r" (sh), "=&r" (sl) \ + : "r" (ah), "r" (bh), "%r" (al), "rI" (bl)); \ } while (0) /* sub_ddmmss is used in op-2.h and udivmodti4.c and should be equivalent to@@ -248,44 +236,24 @@ * and LOW_DIFFERENCE. Overflow (i.e. carry out) is not stored anywhere, * and is lost. */ -#define sub_ddmmss(sh, sl, ah, al, bh, bl) \ +#define sub_ddmmss(sh, sl, ah, al, bh, bl) \ do { \ if (__builtin_constant_p (ah) && (ah) == 0) \ - __asm__ ("{sf%I3|subf%I3c} %1,%4,%3\n\t{sfze|subfze} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "r" ((USItype)(bh)), \ - "rI" ((USItype)(al)), \ - "r" ((USItype)(bl))); \ - else if (__builtin_constant_p (ah) && (ah) ==~(USItype) 0) \ - __asm__ ("{sf%I3|subf%I3c} %1,%4,%3\n\t{sfme|subfme} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "r" ((USItype)(bh)), \ - "rI" ((USItype)(al)), \ - "r" ((USItype)(bl))); \ + __asm__ ("subf%I3c %1,%4,%3\n\tsubfze %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (bh), "rI" (al), "r" (bl));\ + else if (__builtin_constant_p (ah) && (ah) == ~(USItype) 0) \ + __asm__ ("subf%I3c %1,%4,%3\n\tsubfme %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (bh), "rI" (al), "r" (bl));\ else if (__builtin_constant_p (bh) && (bh) == 0) \ - __asm__ ("{sf%I3|subf%I3c} %1,%4,%3\n\t{ame|addme} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "r" ((USItype)(ah)), \ - "rI" ((USItype)(al)), \ - "r" ((USItype)(bl))); \ - else if (__builtin_constant_p (bh) && (bh) ==~(USItype) 0) \ - __asm__ ("{sf%I3|subf%I3c} %1,%4,%3\n\t{aze|addze} %0,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "r" ((USItype)(ah)), \ - "rI" ((USItype)(al)), \ - "r" ((USItype)(bl))); \ + __asm__ ("subf%I3c %1,%4,%3\n\taddme %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (ah), "rI" (al), "r" (bl));\ + else if (__builtin_constant_p (bh) && (bh) == ~(USItype) 0) \ + __asm__ ("subf%I3c %1,%4,%3\n\taddze %0,%2" \ + : "=r" (sh), "=&r" (sl) : "r" (ah), "rI" (al), "r" (bl));\ else \ - __asm__ ("{sf%I4|subf%I4c} %1,%5,%4\n\t{sfe|subfe} %0,%3,%2" \ - : "=r" ((USItype)(sh)), \ - "=&r" ((USItype)(sl)) \ - : "r" ((USItype)(ah)), \ - "r" ((USItype)(bh)), \ - "rI" ((USItype)(al)), \ - "r" ((USItype)(bl))); \ + __asm__ ("subf%I4c %1,%5,%4\n\tsubfe %0,%3,%2" \ + : "=r" (sh), "=&r" (sl) \ + : "r" (ah), "r" (bh), "rI" (al), "r" (bl)); \ } while (0) /* asm fragments for mul and div */@@ -294,13 +262,10 @@ * UWtype integers MULTIPLER and MULTIPLICAND, and generates a two UWtype * word product in HIGH_PROD and LOW_PROD. */ -#define umul_ppmm(ph, pl, m0, m1) \ +#define umul_ppmm(ph, pl, m0, m1) \ do { \ USItype __m0 = (m0), __m1 = (m1); \ - __asm__ ("mulhwu %0,%1,%2" \ - : "=r" ((USItype)(ph)) \ - : "%r" (__m0), \ - "r" (__m1)); \ + __asm__ ("mulhwu %0,%1,%2" : "=r" (ph) : "%r" (m0), "r" (m1)); \ (pl) = __m0 * __m1; \ } while (0)@@ -312,28 +277,28 @@ * significant bit of DENOMINATOR must be 1, then the pre-processor symbol * UDIV_NEEDS_NORMALIZATION is defined to 1. */ -#define udiv_qrnnd(q, r, n1, n0, d) \ +#define udiv_qrnnd(q, r, n1, n0, d) \ do { \ UWtype __d1, __d0, __q1, __q0, __r1, __r0, __m; \ __d1 = __ll_highpart (d); \ __d0 = __ll_lowpart (d); \ \ - __r1 = (n1) % __d1; \ __q1 = (n1) / __d1; \ - __m = (UWtype) __q1 * __d0; \ + __r1 = (n1) - __q1 * __d1; \ + __m = __q1 * __d0; \ __r1 = __r1 * __ll_B | __ll_highpart (n0); \ if (__r1 < __m) \ { \ __q1--, __r1 += (d); \ - if (__r1 >= (d)) /* we didn't get carry when adding to __r1 */ \ + if (__r1 >= (d)) /* i.e. we didn't get carry when adding to __r1 */\ if (__r1 < __m) \ __q1--, __r1 += (d); \ } \ __r1 -= __m; \ \ - __r0 = __r1 % __d1; \ __q0 = __r1 / __d1; \ - __m = (UWtype) __q0 * __d0; \ + __r0 = __r1 - __q0 * __d1; \ + __m = __q0 * __d0; \ __r0 = __r0 * __ll_B | __ll_lowpart (n0); \ if (__r0 < __m) \ { \@@ -344,7 +309,7 @@ } \ __r0 -= __m; \ \ - (q) = (UWtype) __q1 * __ll_B | __q0; \ + (q) = __q1 * __ll_B | __q0; \ (r) = __r0; \ } while (0)
This appears to now differ from the upstream source: https://github.com/gcc-mirror/gcc/blob/f7289f563a5e447ac21a5901ed75aad0dbd37732/include/longlong.h#L1679 If we're going to borrow implementations from GCC, let's borrow the same implementation. Otherwise it's hard to have confidence in this part of the patch. -- Thanks, ~Nick Desaulniers