1//===-- comparesf2.S - Implement single-precision soft-float comparisons --===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the following soft-fp_t comparison routines:
10//
11// __eqsf2 __gesf2 __unordsf2
12// __lesf2 __gtsf2
13// __ltsf2
14// __nesf2
15//
16// The semantics of the routines grouped in each column are identical, so there
17// is a single implementation for each, with multiple names.
18//
19// The routines behave as follows:
20//
21// __lesf2(a,b) returns -1 if a < b
22// 0 if a == b
23// 1 if a > b
24// 1 if either a or b is NaN
25//
26// __gesf2(a,b) returns -1 if a < b
27// 0 if a == b
28// 1 if a > b
29// -1 if either a or b is NaN
30//
31// __unordsf2(a,b) returns 0 if both a and b are numbers
32// 1 if either a or b is NaN
33//
34// Note that __lesf2( ) and __gesf2( ) are identical except in their handling of
35// NaN values.
36//
37//===----------------------------------------------------------------------===//
38
39#include "../assembly.h"
40
41 .syntax unified
42 .text
43 DEFINE_CODE_STATE
44
45 .macro COMPARESF2_FUNCTION_BODY handle_nan:req
46#if defined(COMPILER_RT_ARMHF_TARGET)
47 vmov r0, s0
48 vmov r1, s1
49#endif
50 // Make copies of a and b with the sign bit shifted off the top. These will
51 // be used to detect zeros and NaNs.
52#if defined(USE_THUMB_1)
53 push {r6, lr}
54 lsls r2, r0, #1
55 lsls r3, r1, #1
56#else
57 mov r2, r0, lsl #1
58 mov r3, r1, lsl #1
59#endif
60
61 // We do the comparison in three stages (ignoring NaN values for the time
62 // being). First, we orr the absolute values of a and b; this sets the Z
63 // flag if both a and b are zero (of either sign). The shift of r3 doesn't
64 // effect this at all, but it *does* make sure that the C flag is clear for
65 // the subsequent operations.
66#if defined(USE_THUMB_1)
67 lsrs r6, r3, #1
68 orrs r6, r2
69#else
70 orrs r12, r2, r3, lsr #1
71#endif
72 // Next, we check if a and b have the same or different signs. If they have
73 // opposite signs, this eor will set the N flag.
74#if defined(USE_THUMB_1)
75 beq 1f
76 movs r6, r0
77 eors r6, r1
781:
79#else
80 it ne
81 eorsne r12, r0, r1
82#endif
83
84 // If a and b are equal (either both zeros or bit identical; again, we're
85 // ignoring NaNs for now), this subtract will zero out r0. If they have the
86 // same sign, the flags are updated as they would be for a comparison of the
87 // absolute values of a and b.
88#if defined(USE_THUMB_1)
89 bmi 1f
90 subs r0, r2, r3
911:
92#else
93 it pl
94 subspl r0, r2, r3
95#endif
96
97 // If a is smaller in magnitude than b and both have the same sign, place
98 // the negation of the sign of b in r0. Thus, if both are negative and
99 // a > b, this sets r0 to 0; if both are positive and a < b, this sets
100 // r0 to -1.
101 //
102 // This is also done if a and b have opposite signs and are not both zero,
103 // because in that case the subtract was not performed and the C flag is
104 // still clear from the shift argument in orrs; if a is positive and b
105 // negative, this places 0 in r0; if a is negative and b positive, -1 is
106 // placed in r0.
107#if defined(USE_THUMB_1)
108 bhs 1f
109 // Here if a and b have the same sign and absA < absB, the result is thus
110 // b < 0 ? 1 : -1. Same if a and b have the opposite sign (ignoring Nan).
111 movs r0, #1
112 lsrs r1, #31
113 bne LOCAL_LABEL(CHECK_NAN\@)
114 negs r0, r0
115 b LOCAL_LABEL(CHECK_NAN\@)
1161:
117#else
118 it lo
119 mvnlo r0, r1, asr #31
120#endif
121
122 // If a is greater in magnitude than b and both have the same sign, place
123 // the sign of b in r0. Thus, if both are negative and a < b, -1 is placed
124 // in r0, which is the desired result. Conversely, if both are positive
125 // and a > b, zero is placed in r0.
126#if defined(USE_THUMB_1)
127 bls 1f
128 // Here both have the same sign and absA > absB.
129 movs r0, #1
130 lsrs r1, #31
131 beq LOCAL_LABEL(CHECK_NAN\@)
132 negs r0, r0
1331:
134#else
135 it hi
136 movhi r0, r1, asr #31
137#endif
138
139 // If you've been keeping track, at this point r0 contains -1 if a < b and
140 // 0 if a >= b. All that remains to be done is to set it to 1 if a > b.
141 // If a == b, then the Z flag is set, so we can get the correct final value
142 // into r0 by simply or'ing with 1 if Z is clear.
143 // For Thumb-1, r0 contains -1 if a < b, 0 if a > b and 0 if a == b.
144#if !defined(USE_THUMB_1)
145 it ne
146 orrne r0, r0, #1
147#endif
148
149 // Finally, we need to deal with NaNs. If either argument is NaN, replace
150 // the value in r0 with 1.
151#if defined(USE_THUMB_1)
152LOCAL_LABEL(CHECK_NAN\@):
153 movs r6, #0xff
154 lsls r6, #24
155 cmp r2, r6
156 bhi 1f
157 cmp r3, r6
1581:
159 bls 2f
160 \handle_nan
1612:
162 pop {r6, pc}
163#else
164 cmp r2, #0xff000000
165 ite ls
166 cmpls r3, #0xff000000
167 \handle_nan
168 JMP(lr)
169#endif
170 .endm
171
172@ int __eqsf2(float a, float b)
173
174 .p2align 2
175DEFINE_COMPILERRT_FUNCTION(__eqsf2)
176
177 .macro __eqsf2_handle_nan
178#if defined(USE_THUMB_1)
179 movs r0, #1
180#else
181 movhi r0, #1
182#endif
183 .endm
184
185COMPARESF2_FUNCTION_BODY __eqsf2_handle_nan
186
187END_COMPILERRT_FUNCTION(__eqsf2)
188
189DEFINE_COMPILERRT_FUNCTION_ALIAS(__lesf2, __eqsf2)
190DEFINE_COMPILERRT_FUNCTION_ALIAS(__ltsf2, __eqsf2)
191DEFINE_COMPILERRT_FUNCTION_ALIAS(__nesf2, __eqsf2)
192
193#if defined(__ELF__)
194// Alias for libgcc compatibility
195DEFINE_COMPILERRT_FUNCTION_ALIAS(__cmpsf2, __lesf2)
196#endif
197
198@ int __gtsf2(float a, float b)
199
200 .p2align 2
201DEFINE_COMPILERRT_FUNCTION(__gtsf2)
202
203 .macro __gtsf2_handle_nan
204#if defined(USE_THUMB_1)
205 movs r0, #1
206 negs r0, r0
207#else
208 movhi r0, #-1
209#endif
210 .endm
211
212COMPARESF2_FUNCTION_BODY __gtsf2_handle_nan
213
214END_COMPILERRT_FUNCTION(__gtsf2)
215
216DEFINE_COMPILERRT_FUNCTION_ALIAS(__gesf2, __gtsf2)
217
218@ int __unordsf2(float a, float b)
219
220 .p2align 2
221DEFINE_COMPILERRT_FUNCTION(__unordsf2)
222
223#if defined(COMPILER_RT_ARMHF_TARGET)
224 vmov r0, s0
225 vmov r1, s1
226#endif
227 // Return 1 for NaN values, 0 otherwise.
228 lsls r2, r0, #1
229 lsls r3, r1, #1
230 movs r0, #0
231#if defined(USE_THUMB_1)
232 movs r1, #0xff
233 lsls r1, #24
234 cmp r2, r1
235 bhi 1f
236 cmp r3, r1
2371:
238 bls 2f
239 movs r0, #1
2402:
241#else
242 cmp r2, #0xff000000
243 ite ls
244 cmpls r3, #0xff000000
245 movhi r0, #1
246#endif
247 JMP(lr)
248END_COMPILERRT_FUNCTION(__unordsf2)
249
250#if defined(COMPILER_RT_ARMHF_TARGET)
251DEFINE_COMPILERRT_FUNCTION(__aeabi_fcmpun)
252 vmov s0, r0
253 vmov s1, r1
254 b SYMBOL_NAME(__unordsf2)
255END_COMPILERRT_FUNCTION(__aeabi_fcmpun)
256#else
257DEFINE_AEABI_FUNCTION_ALIAS(__aeabi_fcmpun, __unordsf2)
258#endif
259
260NO_EXEC_STACK_DIRECTIVE
261
262

source code of compiler-rt/lib/builtins/arm/comparesf2.S