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 25 twop64: .quad 0x0000000000000000 26 27 #define TWOp64 twop64-0b(%ecx,%eax,8) 28 29 .text 30 .balign 4 31 DEFINE_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 37 0: 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 45 END_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 #ifndef __ELF__ 56 .const 57 #endif 58 .balign 8 59 twop52: .quad 0x4330000000000000 60 .quad 0x0000000000000fff 61 sticky: .quad 0x0000000000000000 62 .long 0x00000012 63 twelve: .long 0x00000000 64 65 #define TWOp52 twop52-0b(%ecx) 66 #define STICKY sticky-0b(%ecx,%eax,8) 67 68 .text 69 .balign 4 70 DEFINE_COMPILERRT_FUNCTION(__floatundisf) 71 movl 8(%esp), %eax 72 movd 8(%esp), %xmm1 73 movd 4(%esp), %xmm0 74 punpckldq %xmm1, %xmm0 75 76 calll 0f 77 0: popl %ecx 78 shrl %eax // high 31 bits of input as sint32 79 addl $0x7ff80000, %eax 80 sarl $31, %eax // (big input) ? -1 : 0 81 movsd STICKY, %xmm1 // (big input) ? 0xfff : 0 82 movl $12, %edx 83 andl %eax, %edx // (big input) ? 12 : 0 84 movd %edx, %xmm3 85 andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0 86 movsd TWOp52, %xmm2 // 0x1.0p52 87 psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input 88 orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input) 89 orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input) 90 subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input) 91 cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input) 92 pslld $23, %xmm3 93 paddd %xmm3, %xmm0 // (float)input 94 movd %xmm0, 4(%esp) 95 flds 4(%esp) 96 ret 97 END_COMPILERRT_FUNCTION(__floatundisf) 98 99 #endif // __i386__ 100
