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1/* SPDX-License-Identifier: GPL-2.0 */
2#include <linux/export.h>
3#include <linux/linkage.h>
4#include <asm/processor.h>
5#include <asm/ppc_asm.h>
6#include <asm/reg.h>
7#include <asm/asm-offsets.h>
8#include <asm/cputable.h>
9#include <asm/thread_info.h>
10#include <asm/page.h>
11#include <asm/ptrace.h>
12#include <asm/asm-compat.h>
13
14/*
15 * Load state from memory into VMX registers including VSCR.
16 * Assumes the caller has enabled VMX in the MSR.
17 */
18_GLOBAL(load_vr_state)
19 li r4,VRSTATE_VSCR
20 lvx v0,r4,r3
21 mtvscr v0
22 REST_32VRS(0,r4,r3)
23 blr
24EXPORT_SYMBOL(load_vr_state)
25_ASM_NOKPROBE_SYMBOL(load_vr_state); /* used by restore_math */
26
27/*
28 * Store VMX state into memory, including VSCR.
29 * Assumes the caller has enabled VMX in the MSR.
30 */
31_GLOBAL(store_vr_state)
32 SAVE_32VRS(0, r4, r3)
33 mfvscr v0
34 li r4, VRSTATE_VSCR
35 stvx v0, r4, r3
36 lvx v0, 0, r3
37 blr
38EXPORT_SYMBOL(store_vr_state)
39
40/*
41 * Disable VMX for the task which had it previously,
42 * and save its vector registers in its thread_struct.
43 * Enables the VMX for use in the kernel on return.
44 * On SMP we know the VMX is free, since we give it up every
45 * switch (ie, no lazy save of the vector registers).
46 *
47 * Note that on 32-bit this can only use registers that will be
48 * restored by fast_exception_return, i.e. r3 - r6, r10 and r11.
49 */
50_GLOBAL(load_up_altivec)
51 mfmsr r5 /* grab the current MSR */
52#ifdef CONFIG_PPC_BOOK3S_64
53 /* interrupt doesn't set MSR[RI] and HPT can fault on current access */
54 ori r5,r5,MSR_RI
55#endif
56 oris r5,r5,MSR_VEC@h
57 MTMSRD(r5) /* enable use of AltiVec now */
58 isync
59
60 /*
61 * While userspace in general ignores VRSAVE, glibc uses it as a boolean
62 * to optimise userspace context save/restore. Whenever we take an
63 * altivec unavailable exception we must set VRSAVE to something non
64 * zero. Set it to all 1s. See also the programming note in the ISA.
65 */
66 mfspr r4,SPRN_VRSAVE
67 cmpwi 0,r4,0
68 bne+ 1f
69 li r4,-1
70 mtspr SPRN_VRSAVE,r4
711:
72 /* enable use of VMX after return */
73#ifdef CONFIG_PPC32
74 addi r5,r2,THREAD
75 oris r9,r9,MSR_VEC@h
76#else
77 ld r4,PACACURRENT(r13)
78 addi r5,r4,THREAD /* Get THREAD */
79 oris r12,r12,MSR_VEC@h
80 std r12,_MSR(r1)
81#ifdef CONFIG_PPC_BOOK3S_64
82 li r4,0
83 stb r4,PACASRR_VALID(r13)
84#endif
85#endif
86 li r4,1
87 stb r4,THREAD_LOAD_VEC(r5)
88 addi r6,r5,THREAD_VRSTATE
89 li r10,VRSTATE_VSCR
90 stw r4,THREAD_USED_VR(r5)
91 lvx v0,r10,r6
92 mtvscr v0
93 REST_32VRS(0,r4,r6)
94 /* restore registers and return */
95 blr
96_ASM_NOKPROBE_SYMBOL(load_up_altivec)
97
98/*
99 * save_altivec(tsk)
100 * Save the vector registers to its thread_struct
101 */
102_GLOBAL(save_altivec)
103 addi r3,r3,THREAD /* want THREAD of task */
104 PPC_LL r7,THREAD_VRSAVEAREA(r3)
105 PPC_LL r5,PT_REGS(r3)
106 PPC_LCMPI 0,r7,0
107 bne 2f
108 addi r7,r3,THREAD_VRSTATE
1092: SAVE_32VRS(0,r4,r7)
110 mfvscr v0
111 li r4,VRSTATE_VSCR
112 stvx v0,r4,r7
113 lvx v0,0,r7
114 blr
115
116#ifdef CONFIG_VSX
117
118#ifdef CONFIG_PPC32
119#error This asm code isn't ready for 32-bit kernels
120#endif
121
122/*
123 * load_up_vsx(unused, unused, tsk)
124 * Disable VSX for the task which had it previously,
125 * and save its vector registers in its thread_struct.
126 * Reuse the fp and vsx saves, but first check to see if they have
127 * been saved already.
128 */
129_GLOBAL(load_up_vsx)
130/* Load FP and VSX registers if they haven't been done yet */
131 andi. r5,r12,MSR_FP
132 beql+ load_up_fpu /* skip if already loaded */
133 andis. r5,r12,MSR_VEC@h
134 beql+ load_up_altivec /* skip if already loaded */
135
136#ifdef CONFIG_PPC_BOOK3S_64
137 /* interrupt doesn't set MSR[RI] and HPT can fault on current access */
138 li r5,MSR_RI
139 mtmsrd r5,1
140#endif
141
142 ld r4,PACACURRENT(r13)
143 addi r4,r4,THREAD /* Get THREAD */
144 li r6,1
145 stw r6,THREAD_USED_VSR(r4) /* ... also set thread used vsr */
146 /* enable use of VSX after return */
147 oris r12,r12,MSR_VSX@h
148 std r12,_MSR(r1)
149 li r4,0
150 stb r4,PACASRR_VALID(r13)
151 b fast_interrupt_return_srr
152
153#endif /* CONFIG_VSX */
154
155
156/*
157 * The routines below are in assembler so we can closely control the
158 * usage of floating-point registers. These routines must be called
159 * with preempt disabled.
160 */
161 .data
162#ifdef CONFIG_PPC32
163fpzero:
164 .long 0
165fpone:
166 .long 0x3f800000 /* 1.0 in single-precision FP */
167fphalf:
168 .long 0x3f000000 /* 0.5 in single-precision FP */
169
170#define LDCONST(fr, name) \
171 lis r11,name@ha; \
172 lfs fr,name@l(r11)
173#else
174
175fpzero:
176 .quad 0
177fpone:
178 .quad 0x3ff0000000000000 /* 1.0 */
179fphalf:
180 .quad 0x3fe0000000000000 /* 0.5 */
181
182#ifdef CONFIG_PPC_KERNEL_PCREL
183#define LDCONST(fr, name) \
184 pla r11,name@pcrel; \
185 lfd fr,0(r11)
186#else
187#define LDCONST(fr, name) \
188 addis r11,r2,name@toc@ha; \
189 lfd fr,name@toc@l(r11)
190#endif
191#endif
192 .text
193/*
194 * Internal routine to enable floating point and set FPSCR to 0.
195 * Don't call it from C; it doesn't use the normal calling convention.
196 */
197SYM_FUNC_START_LOCAL(fpenable)
198#ifdef CONFIG_PPC32
199 stwu r1,-64(r1)
200#else
201 stdu r1,-64(r1)
202#endif
203 mfmsr r10
204 ori r11,r10,MSR_FP
205 mtmsr r11
206 isync
207 stfd fr0,24(r1)
208 stfd fr1,16(r1)
209 stfd fr31,8(r1)
210 LDCONST(fr1, fpzero)
211 mffs fr31
212 MTFSF_L(fr1)
213 blr
214SYM_FUNC_END(fpenable)
215
216fpdisable:
217 mtlr r12
218 MTFSF_L(fr31)
219 lfd fr31,8(r1)
220 lfd fr1,16(r1)
221 lfd fr0,24(r1)
222 mtmsr r10
223 isync
224 addi r1,r1,64
225 blr
226
227/*
228 * Vector add, floating point.
229 */
230_GLOBAL(vaddfp)
231 mflr r12
232 bl fpenable
233 li r0,4
234 mtctr r0
235 li r6,0
2361: lfsx fr0,r4,r6
237 lfsx fr1,r5,r6
238 fadds fr0,fr0,fr1
239 stfsx fr0,r3,r6
240 addi r6,r6,4
241 bdnz 1b
242 b fpdisable
243
244/*
245 * Vector subtract, floating point.
246 */
247_GLOBAL(vsubfp)
248 mflr r12
249 bl fpenable
250 li r0,4
251 mtctr r0
252 li r6,0
2531: lfsx fr0,r4,r6
254 lfsx fr1,r5,r6
255 fsubs fr0,fr0,fr1
256 stfsx fr0,r3,r6
257 addi r6,r6,4
258 bdnz 1b
259 b fpdisable
260
261/*
262 * Vector multiply and add, floating point.
263 */
264_GLOBAL(vmaddfp)
265 mflr r12
266 bl fpenable
267 stfd fr2,32(r1)
268 li r0,4
269 mtctr r0
270 li r7,0
2711: lfsx fr0,r4,r7
272 lfsx fr1,r5,r7
273 lfsx fr2,r6,r7
274 fmadds fr0,fr0,fr2,fr1
275 stfsx fr0,r3,r7
276 addi r7,r7,4
277 bdnz 1b
278 lfd fr2,32(r1)
279 b fpdisable
280
281/*
282 * Vector negative multiply and subtract, floating point.
283 */
284_GLOBAL(vnmsubfp)
285 mflr r12
286 bl fpenable
287 stfd fr2,32(r1)
288 li r0,4
289 mtctr r0
290 li r7,0
2911: lfsx fr0,r4,r7
292 lfsx fr1,r5,r7
293 lfsx fr2,r6,r7
294 fnmsubs fr0,fr0,fr2,fr1
295 stfsx fr0,r3,r7
296 addi r7,r7,4
297 bdnz 1b
298 lfd fr2,32(r1)
299 b fpdisable
300
301/*
302 * Vector reciprocal estimate. We just compute 1.0/x.
303 * r3 -> destination, r4 -> source.
304 */
305_GLOBAL(vrefp)
306 mflr r12
307 bl fpenable
308 li r0,4
309 LDCONST(fr1, fpone)
310 mtctr r0
311 li r6,0
3121: lfsx fr0,r4,r6
313 fdivs fr0,fr1,fr0
314 stfsx fr0,r3,r6
315 addi r6,r6,4
316 bdnz 1b
317 b fpdisable
318
319/*
320 * Vector reciprocal square-root estimate, floating point.
321 * We use the frsqrte instruction for the initial estimate followed
322 * by 2 iterations of Newton-Raphson to get sufficient accuracy.
323 * r3 -> destination, r4 -> source.
324 */
325_GLOBAL(vrsqrtefp)
326 mflr r12
327 bl fpenable
328 stfd fr2,32(r1)
329 stfd fr3,40(r1)
330 stfd fr4,48(r1)
331 stfd fr5,56(r1)
332 li r0,4
333 LDCONST(fr4, fpone)
334 LDCONST(fr5, fphalf)
335 mtctr r0
336 li r6,0
3371: lfsx fr0,r4,r6
338 frsqrte fr1,fr0 /* r = frsqrte(s) */
339 fmuls fr3,fr1,fr0 /* r * s */
340 fmuls fr2,fr1,fr5 /* r * 0.5 */
341 fnmsubs fr3,fr1,fr3,fr4 /* 1 - s * r * r */
342 fmadds fr1,fr2,fr3,fr1 /* r = r + 0.5 * r * (1 - s * r * r) */
343 fmuls fr3,fr1,fr0 /* r * s */
344 fmuls fr2,fr1,fr5 /* r * 0.5 */
345 fnmsubs fr3,fr1,fr3,fr4 /* 1 - s * r * r */
346 fmadds fr1,fr2,fr3,fr1 /* r = r + 0.5 * r * (1 - s * r * r) */
347 stfsx fr1,r3,r6
348 addi r6,r6,4
349 bdnz 1b
350 lfd fr5,56(r1)
351 lfd fr4,48(r1)
352 lfd fr3,40(r1)
353 lfd fr2,32(r1)
354 b fpdisable
1#include <asm/processor.h>
2#include <asm/ppc_asm.h>
3#include <asm/reg.h>
4#include <asm/asm-offsets.h>
5#include <asm/cputable.h>
6#include <asm/thread_info.h>
7#include <asm/page.h>
8#include <asm/ptrace.h>
9
10/*
11 * load_up_altivec(unused, unused, tsk)
12 * Disable VMX for the task which had it previously,
13 * and save its vector registers in its thread_struct.
14 * Enables the VMX for use in the kernel on return.
15 * On SMP we know the VMX is free, since we give it up every
16 * switch (ie, no lazy save of the vector registers).
17 */
18_GLOBAL(load_up_altivec)
19 mfmsr r5 /* grab the current MSR */
20 oris r5,r5,MSR_VEC@h
21 MTMSRD(r5) /* enable use of AltiVec now */
22 isync
23
24/*
25 * For SMP, we don't do lazy VMX switching because it just gets too
26 * horrendously complex, especially when a task switches from one CPU
27 * to another. Instead we call giveup_altvec in switch_to.
28 * VRSAVE isn't dealt with here, that is done in the normal context
29 * switch code. Note that we could rely on vrsave value to eventually
30 * avoid saving all of the VREGs here...
31 */
32#ifndef CONFIG_SMP
33 LOAD_REG_ADDRBASE(r3, last_task_used_altivec)
34 toreal(r3)
35 PPC_LL r4,ADDROFF(last_task_used_altivec)(r3)
36 PPC_LCMPI 0,r4,0
37 beq 1f
38
39 /* Save VMX state to last_task_used_altivec's THREAD struct */
40 toreal(r4)
41 addi r4,r4,THREAD
42 SAVE_32VRS(0,r5,r4)
43 mfvscr vr0
44 li r10,THREAD_VSCR
45 stvx vr0,r10,r4
46 /* Disable VMX for last_task_used_altivec */
47 PPC_LL r5,PT_REGS(r4)
48 toreal(r5)
49 PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
50 lis r10,MSR_VEC@h
51 andc r4,r4,r10
52 PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
531:
54#endif /* CONFIG_SMP */
55
56 /* Hack: if we get an altivec unavailable trap with VRSAVE
57 * set to all zeros, we assume this is a broken application
58 * that fails to set it properly, and thus we switch it to
59 * all 1's
60 */
61 mfspr r4,SPRN_VRSAVE
62 cmpwi 0,r4,0
63 bne+ 1f
64 li r4,-1
65 mtspr SPRN_VRSAVE,r4
661:
67 /* enable use of VMX after return */
68#ifdef CONFIG_PPC32
69 mfspr r5,SPRN_SPRG_THREAD /* current task's THREAD (phys) */
70 oris r9,r9,MSR_VEC@h
71#else
72 ld r4,PACACURRENT(r13)
73 addi r5,r4,THREAD /* Get THREAD */
74 oris r12,r12,MSR_VEC@h
75 std r12,_MSR(r1)
76#endif
77 li r4,1
78 li r10,THREAD_VSCR
79 stw r4,THREAD_USED_VR(r5)
80 lvx vr0,r10,r5
81 mtvscr vr0
82 REST_32VRS(0,r4,r5)
83#ifndef CONFIG_SMP
84 /* Update last_task_used_altivec to 'current' */
85 subi r4,r5,THREAD /* Back to 'current' */
86 fromreal(r4)
87 PPC_STL r4,ADDROFF(last_task_used_altivec)(r3)
88#endif /* CONFIG_SMP */
89 /* restore registers and return */
90 blr
91
92/*
93 * giveup_altivec(tsk)
94 * Disable VMX for the task given as the argument,
95 * and save the vector registers in its thread_struct.
96 * Enables the VMX for use in the kernel on return.
97 */
98_GLOBAL(giveup_altivec)
99 mfmsr r5
100 oris r5,r5,MSR_VEC@h
101 SYNC
102 MTMSRD(r5) /* enable use of VMX now */
103 isync
104 PPC_LCMPI 0,r3,0
105 beqlr /* if no previous owner, done */
106 addi r3,r3,THREAD /* want THREAD of task */
107 PPC_LL r5,PT_REGS(r3)
108 PPC_LCMPI 0,r5,0
109 SAVE_32VRS(0,r4,r3)
110 mfvscr vr0
111 li r4,THREAD_VSCR
112 stvx vr0,r4,r3
113 beq 1f
114 PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
115#ifdef CONFIG_VSX
116BEGIN_FTR_SECTION
117 lis r3,(MSR_VEC|MSR_VSX)@h
118FTR_SECTION_ELSE
119 lis r3,MSR_VEC@h
120ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX)
121#else
122 lis r3,MSR_VEC@h
123#endif
124 andc r4,r4,r3 /* disable FP for previous task */
125 PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1261:
127#ifndef CONFIG_SMP
128 li r5,0
129 LOAD_REG_ADDRBASE(r4,last_task_used_altivec)
130 PPC_STL r5,ADDROFF(last_task_used_altivec)(r4)
131#endif /* CONFIG_SMP */
132 blr
133
134#ifdef CONFIG_VSX
135
136#ifdef CONFIG_PPC32
137#error This asm code isn't ready for 32-bit kernels
138#endif
139
140/*
141 * load_up_vsx(unused, unused, tsk)
142 * Disable VSX for the task which had it previously,
143 * and save its vector registers in its thread_struct.
144 * Reuse the fp and vsx saves, but first check to see if they have
145 * been saved already.
146 */
147_GLOBAL(load_up_vsx)
148/* Load FP and VSX registers if they haven't been done yet */
149 andi. r5,r12,MSR_FP
150 beql+ load_up_fpu /* skip if already loaded */
151 andis. r5,r12,MSR_VEC@h
152 beql+ load_up_altivec /* skip if already loaded */
153
154#ifndef CONFIG_SMP
155 ld r3,last_task_used_vsx@got(r2)
156 ld r4,0(r3)
157 cmpdi 0,r4,0
158 beq 1f
159 /* Disable VSX for last_task_used_vsx */
160 addi r4,r4,THREAD
161 ld r5,PT_REGS(r4)
162 ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
163 lis r6,MSR_VSX@h
164 andc r6,r4,r6
165 std r6,_MSR-STACK_FRAME_OVERHEAD(r5)
1661:
167#endif /* CONFIG_SMP */
168 ld r4,PACACURRENT(r13)
169 addi r4,r4,THREAD /* Get THREAD */
170 li r6,1
171 stw r6,THREAD_USED_VSR(r4) /* ... also set thread used vsr */
172 /* enable use of VSX after return */
173 oris r12,r12,MSR_VSX@h
174 std r12,_MSR(r1)
175#ifndef CONFIG_SMP
176 /* Update last_task_used_vsx to 'current' */
177 ld r4,PACACURRENT(r13)
178 std r4,0(r3)
179#endif /* CONFIG_SMP */
180 b fast_exception_return
181
182/*
183 * __giveup_vsx(tsk)
184 * Disable VSX for the task given as the argument.
185 * Does NOT save vsx registers.
186 * Enables the VSX for use in the kernel on return.
187 */
188_GLOBAL(__giveup_vsx)
189 mfmsr r5
190 oris r5,r5,MSR_VSX@h
191 mtmsrd r5 /* enable use of VSX now */
192 isync
193
194 cmpdi 0,r3,0
195 beqlr- /* if no previous owner, done */
196 addi r3,r3,THREAD /* want THREAD of task */
197 ld r5,PT_REGS(r3)
198 cmpdi 0,r5,0
199 beq 1f
200 ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
201 lis r3,MSR_VSX@h
202 andc r4,r4,r3 /* disable VSX for previous task */
203 std r4,_MSR-STACK_FRAME_OVERHEAD(r5)
2041:
205#ifndef CONFIG_SMP
206 li r5,0
207 ld r4,last_task_used_vsx@got(r2)
208 std r5,0(r4)
209#endif /* CONFIG_SMP */
210 blr
211
212#endif /* CONFIG_VSX */
213
214
215/*
216 * The routines below are in assembler so we can closely control the
217 * usage of floating-point registers. These routines must be called
218 * with preempt disabled.
219 */
220#ifdef CONFIG_PPC32
221 .data
222fpzero:
223 .long 0
224fpone:
225 .long 0x3f800000 /* 1.0 in single-precision FP */
226fphalf:
227 .long 0x3f000000 /* 0.5 in single-precision FP */
228
229#define LDCONST(fr, name) \
230 lis r11,name@ha; \
231 lfs fr,name@l(r11)
232#else
233
234 .section ".toc","aw"
235fpzero:
236 .tc FD_0_0[TC],0
237fpone:
238 .tc FD_3ff00000_0[TC],0x3ff0000000000000 /* 1.0 */
239fphalf:
240 .tc FD_3fe00000_0[TC],0x3fe0000000000000 /* 0.5 */
241
242#define LDCONST(fr, name) \
243 lfd fr,name@toc(r2)
244#endif
245
246 .text
247/*
248 * Internal routine to enable floating point and set FPSCR to 0.
249 * Don't call it from C; it doesn't use the normal calling convention.
250 */
251fpenable:
252#ifdef CONFIG_PPC32
253 stwu r1,-64(r1)
254#else
255 stdu r1,-64(r1)
256#endif
257 mfmsr r10
258 ori r11,r10,MSR_FP
259 mtmsr r11
260 isync
261 stfd fr0,24(r1)
262 stfd fr1,16(r1)
263 stfd fr31,8(r1)
264 LDCONST(fr1, fpzero)
265 mffs fr31
266 MTFSF_L(fr1)
267 blr
268
269fpdisable:
270 mtlr r12
271 MTFSF_L(fr31)
272 lfd fr31,8(r1)
273 lfd fr1,16(r1)
274 lfd fr0,24(r1)
275 mtmsr r10
276 isync
277 addi r1,r1,64
278 blr
279
280/*
281 * Vector add, floating point.
282 */
283_GLOBAL(vaddfp)
284 mflr r12
285 bl fpenable
286 li r0,4
287 mtctr r0
288 li r6,0
2891: lfsx fr0,r4,r6
290 lfsx fr1,r5,r6
291 fadds fr0,fr0,fr1
292 stfsx fr0,r3,r6
293 addi r6,r6,4
294 bdnz 1b
295 b fpdisable
296
297/*
298 * Vector subtract, floating point.
299 */
300_GLOBAL(vsubfp)
301 mflr r12
302 bl fpenable
303 li r0,4
304 mtctr r0
305 li r6,0
3061: lfsx fr0,r4,r6
307 lfsx fr1,r5,r6
308 fsubs fr0,fr0,fr1
309 stfsx fr0,r3,r6
310 addi r6,r6,4
311 bdnz 1b
312 b fpdisable
313
314/*
315 * Vector multiply and add, floating point.
316 */
317_GLOBAL(vmaddfp)
318 mflr r12
319 bl fpenable
320 stfd fr2,32(r1)
321 li r0,4
322 mtctr r0
323 li r7,0
3241: lfsx fr0,r4,r7
325 lfsx fr1,r5,r7
326 lfsx fr2,r6,r7
327 fmadds fr0,fr0,fr2,fr1
328 stfsx fr0,r3,r7
329 addi r7,r7,4
330 bdnz 1b
331 lfd fr2,32(r1)
332 b fpdisable
333
334/*
335 * Vector negative multiply and subtract, floating point.
336 */
337_GLOBAL(vnmsubfp)
338 mflr r12
339 bl fpenable
340 stfd fr2,32(r1)
341 li r0,4
342 mtctr r0
343 li r7,0
3441: lfsx fr0,r4,r7
345 lfsx fr1,r5,r7
346 lfsx fr2,r6,r7
347 fnmsubs fr0,fr0,fr2,fr1
348 stfsx fr0,r3,r7
349 addi r7,r7,4
350 bdnz 1b
351 lfd fr2,32(r1)
352 b fpdisable
353
354/*
355 * Vector reciprocal estimate. We just compute 1.0/x.
356 * r3 -> destination, r4 -> source.
357 */
358_GLOBAL(vrefp)
359 mflr r12
360 bl fpenable
361 li r0,4
362 LDCONST(fr1, fpone)
363 mtctr r0
364 li r6,0
3651: lfsx fr0,r4,r6
366 fdivs fr0,fr1,fr0
367 stfsx fr0,r3,r6
368 addi r6,r6,4
369 bdnz 1b
370 b fpdisable
371
372/*
373 * Vector reciprocal square-root estimate, floating point.
374 * We use the frsqrte instruction for the initial estimate followed
375 * by 2 iterations of Newton-Raphson to get sufficient accuracy.
376 * r3 -> destination, r4 -> source.
377 */
378_GLOBAL(vrsqrtefp)
379 mflr r12
380 bl fpenable
381 stfd fr2,32(r1)
382 stfd fr3,40(r1)
383 stfd fr4,48(r1)
384 stfd fr5,56(r1)
385 li r0,4
386 LDCONST(fr4, fpone)
387 LDCONST(fr5, fphalf)
388 mtctr r0
389 li r6,0
3901: lfsx fr0,r4,r6
391 frsqrte fr1,fr0 /* r = frsqrte(s) */
392 fmuls fr3,fr1,fr0 /* r * s */
393 fmuls fr2,fr1,fr5 /* r * 0.5 */
394 fnmsubs fr3,fr1,fr3,fr4 /* 1 - s * r * r */
395 fmadds fr1,fr2,fr3,fr1 /* r = r + 0.5 * r * (1 - s * r * r) */
396 fmuls fr3,fr1,fr0 /* r * s */
397 fmuls fr2,fr1,fr5 /* r * 0.5 */
398 fnmsubs fr3,fr1,fr3,fr4 /* 1 - s * r * r */
399 fmadds fr1,fr2,fr3,fr1 /* r = r + 0.5 * r * (1 - s * r * r) */
400 stfsx fr1,r3,r6
401 addi r6,r6,4
402 bdnz 1b
403 lfd fr5,56(r1)
404 lfd fr4,48(r1)
405 lfd fr3,40(r1)
406 lfd fr2,32(r1)
407 b fpdisable