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.align 3
23
24		.quad	0x43f0000000000000
25twop64:	.quad	0x0000000000000000
26
27#define			TWOp64			twop64-0b(%ecx,%eax,8)
28
29.text
30.align 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
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
60twop52: .quad 0x4330000000000000
61		.quad 0x0000000000000fff
62sticky: .quad 0x0000000000000000
63		.long 0x00000012
64twelve:	.long 0x00000000
65
66#define			TWOp52			twop52-0b(%ecx)
67#define			STICKY			sticky-0b(%ecx,%eax,8)
68
69.text
70.align 4
71DEFINE_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
780:	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