1// This file is dual licensed under the MIT and the University of Illinois Open 2// Source Licenses. See LICENSE.TXT for details. 3 4#include "../assembly.h" 5 6// float __floatundisf(du_int a); 7 8// Note that there is a hardware instruction, fildll, that does most of what 9// this function needs to do. However, because of our ia32 ABI, it will take 10// a write-small read-large stall, so the software implementation here is 11// actually several cycles faster. 12 13// This is a branch-free implementation. A branchy implementation might be 14// faster for the common case if you know something a priori about the input 15// distribution. 16 17/* branch-free x87 implementation - one cycle slower than without x87. 18 19#ifdef __i386__ 20 21.const 22.balign 3 23 24 .quad 0x43f0000000000000 25twop64: .quad 0x0000000000000000 26 27#define TWOp64 twop64-0b(%ecx,%eax,8) 28 29.text 30.balign 4 31DEFINE_COMPILERRT_FUNCTION(__floatundisf) 32 movl 8(%esp), %eax 33 movd 8(%esp), %xmm1 34 movd 4(%esp), %xmm0 35 punpckldq %xmm1, %xmm0 36 calll 0f 370: popl %ecx 38 sarl $31, %eax 39 movq %xmm0, 4(%esp) 40 fildll 4(%esp) 41 faddl TWOp64 42 fstps 4(%esp) 43 flds 4(%esp) 44 ret 45END_COMPILERRT_FUNCTION(__floatundisf) 46 47#endif // __i386__ 48 49*/ 50 51/* branch-free, x87-free implementation - faster at the expense of code size */ 52 53#ifdef __i386__ 54 55#if defined(__APPLE__) 56 .const 57#elif defined(__ELF__) 58 .section .rodata 59#else 60 .section .rdata,"rd" 61#endif 62 63 .balign 16 64twop52: 65 .quad 0x4330000000000000 66 .quad 0x0000000000000fff 67 68 .balign 16 69sticky: 70 .quad 0x0000000000000000 71 .long 0x00000012 72 73 .balign 16 74twelve: 75 .long 0x00000000 76 77#define TWOp52 twop52-0b(%ecx) 78#define STICKY sticky-0b(%ecx,%eax,8) 79 80.text 81.balign 4 82DEFINE_COMPILERRT_FUNCTION(__floatundisf) 83 movl 8(%esp), %eax 84 movd 8(%esp), %xmm1 85 movd 4(%esp), %xmm0 86 punpckldq %xmm1, %xmm0 87 88 calll 0f 890: popl %ecx 90 shrl %eax // high 31 bits of input as sint32 91 addl $0x7ff80000, %eax 92 sarl $31, %eax // (big input) ? -1 : 0 93 movsd STICKY, %xmm1 // (big input) ? 0xfff : 0 94 movl $12, %edx 95 andl %eax, %edx // (big input) ? 12 : 0 96 movd %edx, %xmm3 97 andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0 98 movsd TWOp52, %xmm2 // 0x1.0p52 99 psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input 100 orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input) 101 orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input) 102 subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input) 103 cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input) 104 pslld $23, %xmm3 105 paddd %xmm3, %xmm0 // (float)input 106 movd %xmm0, 4(%esp) 107 flds 4(%esp) 108 ret 109END_COMPILERRT_FUNCTION(__floatundisf) 110 111#endif // __i386__ 112