1// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 2// See https://llvm.org/LICENSE.txt for license information. 3// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 4 5#include "../assembly.h" 6 7// float __floatundisf(du_int a); 8 9// Note that there is a hardware instruction, fildll, that does most of what 10// this function needs to do. However, because of our ia32 ABI, it will take 11// a write-small read-large stall, so the software implementation here is 12// actually several cycles faster. 13 14// This is a branch-free implementation. A branchy implementation might be 15// faster for the common case if you know something a priori about the input 16// distribution. 17 18/* branch-free x87 implementation - one cycle slower than without x87. 19 20#ifdef __i386__ 21 22CONST_SECTION 23.balign 3 24 25 .quad 0x43f0000000000000 26twop64: .quad 0x0000000000000000 27 28#define TWOp64 twop64-0b(%ecx,%eax,8) 29 30.text 31.balign 4 32DEFINE_COMPILERRT_FUNCTION(__floatundisf) 33 movl 8(%esp), %eax 34 movd 8(%esp), %xmm1 35 movd 4(%esp), %xmm0 36 punpckldq %xmm1, %xmm0 37 calll 0f 380: popl %ecx 39 sarl $31, %eax 40 movq %xmm0, 4(%esp) 41 fildll 4(%esp) 42 faddl TWOp64 43 fstps 4(%esp) 44 flds 4(%esp) 45 ret 46END_COMPILERRT_FUNCTION(__floatundisf) 47 48#endif // __i386__ 49 50*/ 51 52// branch-free, x87-free implementation - faster at the expense of code size 53 54#ifdef __i386__ 55 56CONST_SECTION 57 58 .balign 16 59twop52: 60 .quad 0x4330000000000000 61 .quad 0x0000000000000fff 62 63 .balign 16 64sticky: 65 .quad 0x0000000000000000 66 .long 0x00000012 67 68 .balign 16 69twelve: 70 .long 0x00000000 71 72#define TWOp52 twop52-0b(%ecx) 73#define STICKY sticky-0b(%ecx,%eax,8) 74 75.text 76.balign 4 77DEFINE_COMPILERRT_FUNCTION(__floatundisf) 78 movl 8(%esp), %eax 79 movd 8(%esp), %xmm1 80 movd 4(%esp), %xmm0 81 punpckldq %xmm1, %xmm0 82 83 calll 0f 840: popl %ecx 85 shrl %eax // high 31 bits of input as sint32 86 addl $0x7ff80000, %eax 87 sarl $31, %eax // (big input) ? -1 : 0 88 movsd STICKY, %xmm1 // (big input) ? 0xfff : 0 89 movl $12, %edx 90 andl %eax, %edx // (big input) ? 12 : 0 91 movd %edx, %xmm3 92 andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0 93 movsd TWOp52, %xmm2 // 0x1.0p52 94 psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input 95 orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input) 96 orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input) 97 subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input) 98 cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input) 99 pslld $23, %xmm3 100 paddd %xmm3, %xmm0 // (float)input 101 movd %xmm0, 4(%esp) 102 flds 4(%esp) 103 ret 104END_COMPILERRT_FUNCTION(__floatundisf) 105 106#endif // __i386__ 107 108NO_EXEC_STACK_DIRECTIVE 109 110