| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| |
| // float __floatundisf(du_int a); |
| |
| // Note that there is a hardware instruction, fildll, that does most of what |
| // this function needs to do. However, because of our ia32 ABI, it will take |
| // a write-small read-large stall, so the software implementation here is |
| // actually several cycles faster. |
| |
| // This is a branch-free implementation. A branchy implementation might be |
| // faster for the common case if you know something a priori about the input |
| // distribution. |
| |
| /* branch-free x87 implementation - one cycle slower than without x87. |
| |
| #ifdef __i386__ |
| |
| .const |
| .align 3 |
| |
| .quad 0x43f0000000000000 |
| twop64: .quad 0x0000000000000000 |
| |
| #define TWOp64 twop64-0b(%ecx,%eax,8) |
| |
| .text |
| .align 4 |
| .globl ___floatundisf |
| ___floatundisf: |
| movl 8(%esp), %eax |
| movd 8(%esp), %xmm1 |
| movd 4(%esp), %xmm0 |
| punpckldq %xmm1, %xmm0 |
| calll 0f |
| 0: popl %ecx |
| sarl $31, %eax |
| movq %xmm0, 4(%esp) |
| fildll 4(%esp) |
| faddl TWOp64 |
| fstps 4(%esp) |
| flds 4(%esp) |
| ret |
| |
| #endif // __i386__ |
| |
| */ |
| |
| /* branch-free, x87-free implementation - faster at the expense of code size */ |
| |
| #ifdef __i386__ |
| |
| .const |
| .align 3 |
| twop52: .quad 0x4330000000000000 |
| .quad 0x0000000000000fff |
| sticky: .quad 0x0000000000000000 |
| .long 0x00000012 |
| twelve: .long 0x00000000 |
| |
| #define TWOp52 twop52-0b(%ecx) |
| #define STICKY sticky-0b(%ecx,%eax,8) |
| |
| .text |
| .align 4 |
| .globl ___floatundisf |
| ___floatundisf: |
| movl 8(%esp), %eax |
| movd 8(%esp), %xmm1 |
| movd 4(%esp), %xmm0 |
| punpckldq %xmm1, %xmm0 |
| |
| calll 0f |
| 0: popl %ecx |
| shrl %eax // high 31 bits of input as sint32 |
| addl $0x7ff80000, %eax |
| sarl $31, %eax // (big input) ? -1 : 0 |
| movsd STICKY, %xmm1 // (big input) ? 0xfff : 0 |
| movl $12, %edx |
| andl %eax, %edx // (big input) ? 12 : 0 |
| movd %edx, %xmm3 |
| andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0 |
| movsd TWOp52, %xmm2 // 0x1.0p52 |
| psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input |
| orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input) |
| orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input) |
| subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input) |
| cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input) |
| pslld $23, %xmm3 |
| paddd %xmm3, %xmm0 // (float)input |
| movd %xmm0, 4(%esp) |
| flds 4(%esp) |
| ret |
| |
| #endif // __i386__ |