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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 | /* mul.S: This routine was taken from glibc-1.09 and is covered * by the GNU Library General Public License Version 2. */ /* * Signed multiply, from Appendix E of the Sparc Version 8 * Architecture Manual. */ /* * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of * the 64-bit product). * * This code optimizes short (less than 13-bit) multiplies. */ .globl .mul .mul: mov %o0, %y ! multiplier -> Y andncc %o0, 0xfff, %g0 ! test bits 12..31 be Lmul_shortway ! if zero, can do it the short way andcc %g0, %g0, %o4 ! zero the partial product and clear N and V /* * Long multiply. 32 steps, followed by a final shift step. */ mulscc %o4, %o1, %o4 ! 1 mulscc %o4, %o1, %o4 ! 2 mulscc %o4, %o1, %o4 ! 3 mulscc %o4, %o1, %o4 ! 4 mulscc %o4, %o1, %o4 ! 5 mulscc %o4, %o1, %o4 ! 6 mulscc %o4, %o1, %o4 ! 7 mulscc %o4, %o1, %o4 ! 8 mulscc %o4, %o1, %o4 ! 9 mulscc %o4, %o1, %o4 ! 10 mulscc %o4, %o1, %o4 ! 11 mulscc %o4, %o1, %o4 ! 12 mulscc %o4, %o1, %o4 ! 13 mulscc %o4, %o1, %o4 ! 14 mulscc %o4, %o1, %o4 ! 15 mulscc %o4, %o1, %o4 ! 16 mulscc %o4, %o1, %o4 ! 17 mulscc %o4, %o1, %o4 ! 18 mulscc %o4, %o1, %o4 ! 19 mulscc %o4, %o1, %o4 ! 20 mulscc %o4, %o1, %o4 ! 21 mulscc %o4, %o1, %o4 ! 22 mulscc %o4, %o1, %o4 ! 23 mulscc %o4, %o1, %o4 ! 24 mulscc %o4, %o1, %o4 ! 25 mulscc %o4, %o1, %o4 ! 26 mulscc %o4, %o1, %o4 ! 27 mulscc %o4, %o1, %o4 ! 28 mulscc %o4, %o1, %o4 ! 29 mulscc %o4, %o1, %o4 ! 30 mulscc %o4, %o1, %o4 ! 31 mulscc %o4, %o1, %o4 ! 32 mulscc %o4, %g0, %o4 ! final shift ! If %o0 was negative, the result is ! (%o0 * %o1) + (%o1 << 32)) ! We fix that here. #if 0 tst %o0 bge 1f rd %y, %o0 ! %o0 was indeed negative; fix upper 32 bits of result by subtracting ! %o1 (i.e., return %o4 - %o1 in %o1). retl sub %o4, %o1, %o1 1: retl mov %o4, %o1 #else /* Faster code adapted from tege@sics.se's code for umul.S. */ sra %o0, 31, %o2 ! make mask from sign bit and %o1, %o2, %o2 ! %o2 = 0 or %o1, depending on sign of %o0 rd %y, %o0 ! get lower half of product retl sub %o4, %o2, %o1 ! subtract compensation ! and put upper half in place #endif Lmul_shortway: /* * Short multiply. 12 steps, followed by a final shift step. * The resulting bits are off by 12 and (32-12) = 20 bit positions, * but there is no problem with %o0 being negative (unlike above). */ mulscc %o4, %o1, %o4 ! 1 mulscc %o4, %o1, %o4 ! 2 mulscc %o4, %o1, %o4 ! 3 mulscc %o4, %o1, %o4 ! 4 mulscc %o4, %o1, %o4 ! 5 mulscc %o4, %o1, %o4 ! 6 mulscc %o4, %o1, %o4 ! 7 mulscc %o4, %o1, %o4 ! 8 mulscc %o4, %o1, %o4 ! 9 mulscc %o4, %o1, %o4 ! 10 mulscc %o4, %o1, %o4 ! 11 mulscc %o4, %o1, %o4 ! 12 mulscc %o4, %g0, %o4 ! final shift /* * %o4 has 20 of the bits that should be in the low part of the * result; %y has the bottom 12 (as %y's top 12). That is: * * %o4 %y * +----------------+----------------+ * | -12- | -20- | -12- | -20- | * +------(---------+------)---------+ * --hi-- ----low-part---- * * The upper 12 bits of %o4 should be sign-extended to form the * high part of the product (i.e., highpart = %o4 >> 20). */ rd %y, %o5 sll %o4, 12, %o0 ! shift middle bits left 12 srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left or %o5, %o0, %o0 ! construct low part of result retl sra %o4, 20, %o1 ! ... and extract high part of result |