Warning: That file was not part of the compilation database. It may have many parsing errors.

1 | /* Copyright (C) 2004-2019 Free Software Foundation, Inc. |
---|---|

2 | This file is part of the GNU C Library. |

3 | |

4 | The GNU C Library is free software; you can redistribute it and/or |

5 | modify it under the terms of the GNU Lesser General Public |

6 | License as published by the Free Software Foundation; either |

7 | version 2.1 of the License, or (at your option) any later version. |

8 | |

9 | The GNU C Library is distributed in the hope that it will be useful, |

10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |

11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |

12 | Lesser General Public License for more details. |

13 | |

14 | You should have received a copy of the GNU Lesser General Public |

15 | License along with the GNU C Library. If not, see |

16 | <http://www.gnu.org/licenses/>. */ |

17 | |

18 | #include "div_libc.h" |

19 | |

20 | |

21 | /* 64-bit signed long divide. These are not normal C functions. Argument |

22 | registers are t10 and t11, the result goes in t12. Only t12 and AT may |

23 | be clobbered. |

24 | |

25 | Theory of operation here is that we can use the FPU divider for virtually |

26 | all operands that we see: all dividend values between -2**53 and 2**53-1 |

27 | can be computed directly. Note that divisor values need not be checked |

28 | against that range because the rounded fp value will be close enough such |

29 | that the quotient is < 1, which will properly be truncated to zero when we |

30 | convert back to integer. |

31 | |

32 | When the dividend is outside the range for which we can compute exact |

33 | results, we use the fp quotent as an estimate from which we begin refining |

34 | an exact integral value. This reduces the number of iterations in the |

35 | shift-and-subtract loop significantly. |

36 | |

37 | The FPCR save/restore is due to the fact that the EV6 _will_ set FPCR_INE |

38 | for cvttq/c even without /sui being set. It will not, however, properly |

39 | raise the exception, so we don't have to worry about FPCR_INED being clear |

40 | and so dying by SIGFPE. */ |

41 | |

42 | .text |

43 | .align 4 |

44 | .globl __divq |

45 | .type __divq, @funcnoplt |

46 | .usepv __divq, no |

47 | |

48 | cfi_startproc |

49 | cfi_return_column (RA) |

50 | __divq: |

51 | lda sp, -FRAME(sp) |

52 | cfi_def_cfa_offset (FRAME) |

53 | CALL_MCOUNT |

54 | |

55 | /* Get the fp divide insn issued as quickly as possible. After |

56 | that's done, we have at least 22 cycles until its results are |

57 | ready -- all the time in the world to figure out how we're |

58 | going to use the results. */ |

59 | stt $f0, 0(sp) |

60 | excb |

61 | beq Y, DIVBYZERO |

62 | |

63 | stt $f1, 8(sp) |

64 | stt $f3, 48(sp) |

65 | cfi_rel_offset ($f0, 0) |

66 | cfi_rel_offset ($f1, 8) |

67 | cfi_rel_offset ($f3, 48) |

68 | mf_fpcr $f3 |

69 | |

70 | _ITOFT2 X, $f0, 16, Y, $f1, 24 |

71 | cvtqt $f0, $f0 |

72 | cvtqt $f1, $f1 |

73 | divt/c $f0, $f1, $f0 |

74 | |

75 | /* Check to see if X fit in the double as an exact value. */ |

76 | sll X, (64-53), AT |

77 | ldt $f1, 8(sp) |

78 | sra AT, (64-53), AT |

79 | cmpeq X, AT, AT |

80 | beq AT, $x_big |

81 | |

82 | /* If we get here, we're expecting exact results from the division. |

83 | Do nothing else besides convert and clean up. */ |

84 | cvttq/c $f0, $f0 |

85 | excb |

86 | mt_fpcr $f3 |

87 | _FTOIT $f0, RV, 16 |

88 | |

89 | ldt $f0, 0(sp) |

90 | ldt $f3, 48(sp) |

91 | cfi_restore ($f1) |

92 | cfi_remember_state |

93 | cfi_restore ($f0) |

94 | cfi_restore ($f3) |

95 | cfi_def_cfa_offset (0) |

96 | lda sp, FRAME(sp) |

97 | ret $31, (RA), 1 |

98 | |

99 | .align 4 |

100 | cfi_restore_state |

101 | $x_big: |

102 | /* If we get here, X is large enough that we don't expect exact |

103 | results, and neither X nor Y got mis-translated for the fp |

104 | division. Our task is to take the fp result, figure out how |

105 | far it's off from the correct result and compute a fixup. */ |

106 | stq t0, 16(sp) |

107 | stq t1, 24(sp) |

108 | stq t2, 32(sp) |

109 | stq t5, 40(sp) |

110 | cfi_rel_offset (t0, 16) |

111 | cfi_rel_offset (t1, 24) |

112 | cfi_rel_offset (t2, 32) |

113 | cfi_rel_offset (t5, 40) |

114 | |

115 | #define Q RV /* quotient */ |

116 | #define R t0 /* remainder */ |

117 | #define SY t1 /* scaled Y */ |

118 | #define S t2 /* scalar */ |

119 | #define QY t3 /* Q*Y */ |

120 | |

121 | /* The fixup code below can only handle unsigned values. */ |

122 | or X, Y, AT |

123 | mov $31, t5 |

124 | blt AT, $fix_sign_in |

125 | $fix_sign_in_ret1: |

126 | cvttq/c $f0, $f0 |

127 | |

128 | _FTOIT $f0, Q, 8 |

129 | .align 3 |

130 | $fix_sign_in_ret2: |

131 | ldt $f0, 0(sp) |

132 | stq t3, 0(sp) |

133 | cfi_restore ($f0) |

134 | cfi_rel_offset (t3, 0) |

135 | |

136 | mulq Q, Y, QY |

137 | excb |

138 | stq t4, 8(sp) |

139 | mt_fpcr $f3 |

140 | cfi_rel_offset (t4, 8) |

141 | |

142 | subq QY, X, R |

143 | mov Y, SY |

144 | mov 1, S |

145 | bgt R, $q_high |

146 | |

147 | $q_high_ret: |

148 | subq X, QY, R |

149 | mov Y, SY |

150 | mov 1, S |

151 | bgt R, $q_low |

152 | |

153 | $q_low_ret: |

154 | ldq t0, 16(sp) |

155 | ldq t1, 24(sp) |

156 | ldq t2, 32(sp) |

157 | bne t5, $fix_sign_out |

158 | |

159 | $fix_sign_out_ret: |

160 | ldq t3, 0(sp) |

161 | ldq t4, 8(sp) |

162 | ldq t5, 40(sp) |

163 | ldt $f3, 48(sp) |

164 | lda sp, FRAME(sp) |

165 | cfi_remember_state |

166 | cfi_restore (t0) |

167 | cfi_restore (t1) |

168 | cfi_restore (t2) |

169 | cfi_restore (t3) |

170 | cfi_restore (t4) |

171 | cfi_restore (t5) |

172 | cfi_restore ($f3) |

173 | cfi_def_cfa_offset (0) |

174 | ret $31, (RA), 1 |

175 | |

176 | .align 4 |

177 | cfi_restore_state |

178 | /* The quotient that we computed was too large. We need to reduce |

179 | it by S such that Y*S >= R. Obviously the closer we get to the |

180 | correct value the better, but overshooting high is ok, as we'll |

181 | fix that up later. */ |

182 | 0: |

183 | addq SY, SY, SY |

184 | addq S, S, S |

185 | $q_high: |

186 | cmpult SY, R, AT |

187 | bne AT, 0b |

188 | |

189 | subq Q, S, Q |

190 | unop |

191 | subq QY, SY, QY |

192 | br $q_high_ret |

193 | |

194 | .align 4 |

195 | /* The quotient that we computed was too small. Divide Y by the |

196 | current remainder (R) and add that to the existing quotient (Q). |

197 | The expectation, of course, is that R is much smaller than X. */ |

198 | /* Begin with a shift-up loop. Compute S such that Y*S >= R. We |

199 | already have a copy of Y in SY and the value 1 in S. */ |

200 | 0: |

201 | addq SY, SY, SY |

202 | addq S, S, S |

203 | $q_low: |

204 | cmpult SY, R, AT |

205 | bne AT, 0b |

206 | |

207 | /* Shift-down and subtract loop. Each iteration compares our scaled |

208 | Y (SY) with the remainder (R); if SY <= R then X is divisible by |

209 | Y's scalar (S) so add it to the quotient (Q). */ |

210 | 2: addq Q, S, t3 |

211 | srl S, 1, S |

212 | cmpule SY, R, AT |

213 | subq R, SY, t4 |

214 | |

215 | cmovne AT, t3, Q |

216 | cmovne AT, t4, R |

217 | srl SY, 1, SY |

218 | bne S, 2b |

219 | |

220 | br $q_low_ret |

221 | |

222 | .align 4 |

223 | $fix_sign_in: |

224 | /* If we got here, then X|Y is negative. Need to adjust everything |

225 | such that we're doing unsigned division in the fixup loop. */ |

226 | /* T5 records the changes we had to make: |

227 | bit 0: set if result should be negative. |

228 | bit 2: set if X was negated. |

229 | bit 3: set if Y was negated. |

230 | */ |

231 | xor X, Y, AT |

232 | cmplt AT, 0, t5 |

233 | cmplt X, 0, AT |

234 | negq X, t0 |

235 | |

236 | s4addq AT, t5, t5 |

237 | cmovne AT, t0, X |

238 | cmplt Y, 0, AT |

239 | negq Y, t0 |

240 | |

241 | s8addq AT, t5, t5 |

242 | cmovne AT, t0, Y |

243 | unop |

244 | blbc t5, $fix_sign_in_ret1 |

245 | |

246 | cvttq/c $f0, $f0 |

247 | _FTOIT $f0, Q, 8 |

248 | .align 3 |

249 | negq Q, Q |

250 | br $fix_sign_in_ret2 |

251 | |

252 | .align 4 |

253 | $fix_sign_out: |

254 | /* Now we get to undo what we did above. */ |

255 | /* ??? Is this really faster than just increasing the size of |

256 | the stack frame and storing X and Y in memory? */ |

257 | and t5, 8, AT |

258 | negq Y, t4 |

259 | cmovne AT, t4, Y |

260 | |

261 | and t5, 4, AT |

262 | negq X, t4 |

263 | cmovne AT, t4, X |

264 | |

265 | negq RV, t4 |

266 | cmovlbs t5, t4, RV |

267 | |

268 | br $fix_sign_out_ret |

269 | |

270 | cfi_endproc |

271 | .size __divq, .-__divq |

272 | |

273 | DO_DIVBYZERO |

274 |

Warning: That file was not part of the compilation database. It may have many parsing errors.