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