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[Qemu-devel] [PATCH 61/65] qemu/host-utils.h: Reduce the operation count
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 61/65] qemu/host-utils.h: Reduce the operation count in the fallback ctpop |
Date: |
Fri, 23 Dec 2016 20:00:38 -0800 |
Reviewed-by: Alex Bennée <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
include/qemu/host-utils.h | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 46187bb..96288d0 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -327,7 +327,7 @@ static inline int ctpop8(uint8_t val)
#else
val = (val & 0x55) + ((val >> 1) & 0x55);
val = (val & 0x33) + ((val >> 2) & 0x33);
- val = (val & 0x0f) + ((val >> 4) & 0x0f);
+ val = (val + (val >> 4)) & 0x0f;
return val;
#endif
@@ -344,8 +344,8 @@ static inline int ctpop16(uint16_t val)
#else
val = (val & 0x5555) + ((val >> 1) & 0x5555);
val = (val & 0x3333) + ((val >> 2) & 0x3333);
- val = (val & 0x0f0f) + ((val >> 4) & 0x0f0f);
- val = (val & 0x00ff) + ((val >> 8) & 0x00ff);
+ val = (val + (val >> 4)) & 0x0f0f;
+ val = (val + (val >> 8)) & 0x00ff;
return val;
#endif
@@ -360,11 +360,10 @@ static inline int ctpop32(uint32_t val)
#if QEMU_GNUC_PREREQ(3, 4)
return __builtin_popcount(val);
#else
- val = (val & 0x55555555) + ((val >> 1) & 0x55555555);
- val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
- val = (val & 0x0f0f0f0f) + ((val >> 4) & 0x0f0f0f0f);
- val = (val & 0x00ff00ff) + ((val >> 8) & 0x00ff00ff);
- val = (val & 0x0000ffff) + ((val >> 16) & 0x0000ffff);
+ val = (val & 0x55555555) + ((val >> 1) & 0x55555555);
+ val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
+ val = (val + (val >> 4)) & 0x0f0f0f0f;
+ val = (val * 0x01010101) >> 24;
return val;
#endif
@@ -379,12 +378,10 @@ static inline int ctpop64(uint64_t val)
#if QEMU_GNUC_PREREQ(3, 4)
return __builtin_popcountll(val);
#else
- val = (val & 0x5555555555555555ULL) + ((val >> 1) &
0x5555555555555555ULL);
- val = (val & 0x3333333333333333ULL) + ((val >> 2) &
0x3333333333333333ULL);
- val = (val & 0x0f0f0f0f0f0f0f0fULL) + ((val >> 4) &
0x0f0f0f0f0f0f0f0fULL);
- val = (val & 0x00ff00ff00ff00ffULL) + ((val >> 8) &
0x00ff00ff00ff00ffULL);
- val = (val & 0x0000ffff0000ffffULL) + ((val >> 16) &
0x0000ffff0000ffffULL);
- val = (val & 0x00000000ffffffffULL) + ((val >> 32) &
0x00000000ffffffffULL);
+ val = (val & 0x5555555555555555ULL) + ((val >> 1) & 0x5555555555555555ULL);
+ val = (val & 0x3333333333333333ULL) + ((val >> 2) & 0x3333333333333333ULL);
+ val = (val + (val >> 4)) & 0x0f0f0f0f0f0f0f0fULL;
+ val = (val * 0x0101010101010101ULL) >> 56;
return val;
#endif
--
2.9.3
- [Qemu-devel] [PATCH 53/65] target-xtensa: Use clrsb helper, (continued)
- [Qemu-devel] [PATCH 53/65] target-xtensa: Use clrsb helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 50/65] tcg: Add helpers for clrsb, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 56/65] target-ppc: Use ctpop helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 59/65] target-tilegx: Use ctpop helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 46/65] tcg/i386: Hoist common arguments in tcg_out_op, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 48/65] tcg/i386: Handle ctz and clz opcodes, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 51/65] target-arm: Use clrsb helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 55/65] target-alpha: Use ctpop helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 57/65] target-s390x: Avoid a loop for popcnt, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 54/65] tcg: Add opcode for ctpop, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 61/65] qemu/host-utils.h: Reduce the operation count in the fallback ctpop,
Richard Henderson <=
- [Qemu-devel] [PATCH 60/65] target-i386: Use ctpop helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 49/65] tcg/i386: Rely on undefined/undocumented behaviour of BSF/BSR, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 58/65] target-sparc: Use ctpop helper, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 65/65] tcg/i386: Handle ctpop opcode, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 62/65] tests: New test-bitcnt, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 63/65] tcg: Use ctpop to generate ctz if needed, Richard Henderson, 2016/12/23
- [Qemu-devel] [PATCH 64/65] tcg/ppc: Handle ctpop opcode, Richard Henderson, 2016/12/23