1 // This file is distributed under the University of Illinois Open Source 2 // License. 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 .align 3 23 24 .quad 0x43f0000000000000 25 twop64: .quad 0x0000000000000000 26 27 #define TWOp64 twop64-0b(%ecx,%eax,8) 28 29 .text 30 .align 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 46 #endif // __i386__ 47 48 */ 49 50 /* branch-free, x87-free implementation - faster at the expense of code size */ 51 52 #ifdef __i386__ 53 54 #ifndef __ELF__ 55 .const 56 .align 3 57 #else 58 .align 8 59 #endif 60 twop52: .quad 0x4330000000000000 61 .quad 0x0000000000000fff 62 sticky: .quad 0x0000000000000000 63 .long 0x00000012 64 twelve: .long 0x00000000 65 66 #define TWOp52 twop52-0b(%ecx) 67 #define STICKY sticky-0b(%ecx,%eax,8) 68 69 .text 70 .align 4 71 DEFINE_COMPILERRT_FUNCTION(__floatundisf) 72 movl 8(%esp), %eax 73 movd 8(%esp), %xmm1 74 movd 4(%esp), %xmm0 75 punpckldq %xmm1, %xmm0 76 77 calll 0f 78 0: popl %ecx 79 shrl %eax // high 31 bits of input as sint32 80 addl $0x7ff80000, %eax 81 sarl $31, %eax // (big input) ? -1 : 0 82 movsd STICKY, %xmm1 // (big input) ? 0xfff : 0 83 movl $12, %edx 84 andl %eax, %edx // (big input) ? 12 : 0 85 movd %edx, %xmm3 86 andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0 87 movsd TWOp52, %xmm2 // 0x1.0p52 88 psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input 89 orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input) 90 orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input) 91 subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input) 92 cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input) 93 pslld $23, %xmm3 94 paddd %xmm3, %xmm0 // (float)input 95 movd %xmm0, 4(%esp) 96 flds 4(%esp) 97 ret 98 99 #endif // __i386__ 100
