From bd116582e8eafd2acf67e497af3a90c1b7ac26e1 Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Mon, 8 Oct 2018 11:00:41 -0400 Subject: [PATCH] softfloat: Replace countLeadingZeros32/64 with clz32/64 Our minimum required compiler for compiling QEMU is GCC 4.1 these days, so we can drop the support for compilers which do not provide the __builtin_clz*() functions yet. Since the countLeadingZeros32/64 are then identical to the clz32/64 functions, and we do not have to sync the softloat 2 codebase with upstream anymore (softloat 3 is a complete rewrite) we can simply replace the functions with our QEMU versions. Backports commit 0019d5c3a18c31604fb55f9cec3ceb13999c4866 from qemu --- qemu/fpu/softfloat-macros.h | 87 ------------------------------------- qemu/fpu/softfloat.c | 26 +++++------ 2 files changed, 13 insertions(+), 100 deletions(-) diff --git a/qemu/fpu/softfloat-macros.h b/qemu/fpu/softfloat-macros.h index 9e2e9c71..84f1c225 100644 --- a/qemu/fpu/softfloat-macros.h +++ b/qemu/fpu/softfloat-macros.h @@ -79,17 +79,6 @@ this code that are retained. * version 2 or later. See the COPYING file in the top-level directory. */ -/*---------------------------------------------------------------------------- -| This macro tests for minimum version of the GNU C compiler. -*----------------------------------------------------------------------------*/ -#if defined(__GNUC__) && defined(__GNUC_MINOR__) -# define SOFTFLOAT_GNUC_PREREQ(maj, min) \ - ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min)) -#else -# define SOFTFLOAT_GNUC_PREREQ(maj, min) 0 -#endif - - /*---------------------------------------------------------------------------- | Shifts `a' right by the number of bits given in `count'. If any nonzero | bits are shifted off, they are ``jammed'' into the least significant bit of @@ -712,82 +701,6 @@ static inline uint32_t estimateSqrt32(int aExp, uint32_t a) } -/*---------------------------------------------------------------------------- -| Returns the number of leading 0 bits before the most-significant 1 bit of -| `a'. If `a' is zero, 32 is returned. -*----------------------------------------------------------------------------*/ - -static inline int8_t countLeadingZeros32(uint32_t a) -{ -#if SOFTFLOAT_GNUC_PREREQ(3, 4) - if (a) { - return __builtin_clz(a); - } else { - return 32; - } -#else - static const int8_t countLeadingZerosHigh[] = { - 8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, - 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, - 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, - 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, - 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, - 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, - 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, - 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 - }; - int8_t shiftCount; - - shiftCount = 0; - if ( a < 0x10000 ) { - shiftCount += 16; - a <<= 16; - } - if ( a < 0x1000000 ) { - shiftCount += 8; - a <<= 8; - } - shiftCount += countLeadingZerosHigh[ a>>24 ]; - return shiftCount; -#endif -} - -/*---------------------------------------------------------------------------- -| Returns the number of leading 0 bits before the most-significant 1 bit of -| `a'. If `a' is zero, 64 is returned. -*----------------------------------------------------------------------------*/ - -static inline int8_t countLeadingZeros64(uint64_t a) -{ -#if SOFTFLOAT_GNUC_PREREQ(3, 4) - if (a) { - return __builtin_clzll(a); - } else { - return 64; - } -#else - int8_t shiftCount; - - shiftCount = 0; - if ( a < ( (uint64_t) 1 )<<32 ) { - shiftCount += 32; - } - else { - a >>= 32; - } - shiftCount += countLeadingZeros32( (uint32_t)a ); - return shiftCount; -#endif -} - /*---------------------------------------------------------------------------- | Returns 1 if the 128-bit value formed by concatenating `a0' and `a1' | is equal to the 128-bit value formed by concatenating `b0' and `b1'. diff --git a/qemu/fpu/softfloat.c b/qemu/fpu/softfloat.c index a937205f..9be530c5 100644 --- a/qemu/fpu/softfloat.c +++ b/qemu/fpu/softfloat.c @@ -2683,7 +2683,7 @@ static void { int8_t shiftCount; - shiftCount = countLeadingZeros32( aSig ) - 8; + shiftCount = clz32(aSig) - 8; *zSigPtr = aSig<>( - shiftCount ); *zSig1Ptr = aSig1<<( shiftCount & 63 ); @@ -3308,7 +3308,7 @@ static void *zExpPtr = - shiftCount - 63; } else { - shiftCount = countLeadingZeros64( aSig0 ) - 15; + shiftCount = clz64(aSig0) - 15; shortShift128Left( aSig0, aSig1, shiftCount, zSig0Ptr, zSig1Ptr ); *zExpPtr = 1 - shiftCount; } @@ -3497,7 +3497,7 @@ static float128 normalizeRoundAndPackFloat128(flag zSign, int32_t zExp, zSig1 = 0; zExp -= 64; } - shiftCount = countLeadingZeros64( zSig0 ) - 15; + shiftCount = clz64(zSig0) - 15; if ( 0 <= shiftCount ) { zSig2 = 0; shortShift128Left( zSig0, zSig1, shiftCount, &zSig0, &zSig1 ); @@ -3529,7 +3529,7 @@ floatx80 int32_to_floatx80(int32_t a, float_status *status) if ( a == 0 ) return packFloatx80( 0, 0, 0 ); zSign = ( a < 0 ); absA = zSign ? - a : a; - shiftCount = countLeadingZeros32( absA ) + 32; + shiftCount = clz32(absA) + 32; zSig = absA; return packFloatx80( zSign, 0x403E - shiftCount, zSig<