Bug Summary

File:src/lib/libm/src/s_remquo.c
Warning:line 122, column 38
The result of the left shift is undefined because the left operand is negative

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.4 -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name s_remquo.c -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/lib/libm/obj -resource-dir /usr/local/llvm16/lib/clang/16 -include namespace.h -I /usr/src/lib/libm/arch/amd64 -I /usr/src/lib/libm/src -I /usr/src/lib/libm/src/ld80 -I /usr/src/lib/libm/hidden -internal-isystem /usr/local/llvm16/lib/clang/16/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/lib/libm/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fcf-protection=branch -fno-jump-tables -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/scan/2024-01-11-140451-98009-1 -x c /usr/src/lib/libm/src/s_remquo.c
1/* @(#)e_fmod.c 1.3 95/01/18 */
2/*-
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunSoft, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include <float.h>
14#include <math.h>
15
16#include "math_private.h"
17
18static const double Zero[] = {0.0, -0.0,};
19
20/*
21 * Return the IEEE remainder and set *quo to the last n bits of the
22 * quotient, rounded to the nearest integer. We choose n=31 because
23 * we wind up computing all the integer bits of the quotient anyway as
24 * a side-effect of computing the remainder by the shift and subtract
25 * method. In practice, this is far more bits than are needed to use
26 * remquo in reduction algorithms.
27 */
28double
29remquo(double x, double y, int *quo)
30{
31 int32_t n,hx,hy,hz,ix,iy,sx,i;
32 u_int32_t lx,ly,lz,q,sxy;
33
34 EXTRACT_WORDS(hx,lx,x)do { ieee_double_shape_type ew_u; ew_u.value = (x); (hx) = ew_u
.parts.msw; (lx) = ew_u.parts.lsw; } while (0);
1
Loop condition is false. Exiting loop
→
35 EXTRACT_WORDS(hy,ly,y)do { ieee_double_shape_type ew_u; ew_u.value = (y); (hy) = ew_u
.parts.msw; (ly) = ew_u.parts.lsw; } while (0);
2
←
Loop condition is false. Exiting loop
→
36 sxy = (hx ^ hy) & 0x80000000;
37 sx = hx&0x80000000; /* sign of x */
38 hx ^=sx; /* |x| */
39 hy &= 0x7fffffff; /* |y| */
40
41 /* purge off exception values */
42 if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
3
←
Assuming the condition is false
→
4
←
Assuming 'hx' is < 2146435072
→
6
←
Taking false branch
→
43 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
5
←
Assuming the condition is false
→
44 return (x*y)/(x*y);
45 if(hx<=hy) {
7
←
Assuming 'hx' is > 'hy'
→
8
←
Taking false branch
→
46 if((hx<hy)||(lx<ly)) {
47 q = 0;
48 goto fixup; /* |x|<|y| return x or x-y */
49 }
50 if(lx==ly) {
51 *quo = 1;
52 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
53 }
54 }
55
56 /* determine ix = ilogb(x) */
57 if(hx<0x00100000) { /* subnormal x */
9
←
Assuming 'hx' is >= 1048576
→
10
←
Taking false branch
→
58 if(hx==0) {
59 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
60 } else {
61 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
62 }
63 } else ix = (hx>>20)-1023;
64
65 /* determine iy = ilogb(y) */
66 if(hy<0x00100000) { /* subnormal y */
11
←
Assuming 'hy' is >= 1048576
→
12
←
Taking false branch
→
67 if(hy==0) {
68 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
69 } else {
70 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
71 }
72 } else iy = (hy>>20)-1023;
73
74 /* set up {hx,lx}, {hy,ly} and align y to x */
75 if(ix >= -1022)
13
←
Assuming the condition is false
→
14
←
Taking false branch
→
76 hx = 0x00100000|(0x000fffff&hx);
77 else { /* subnormal x, shift x to normal */
78 n = -1022-ix;
79 if(n<=31) {
15
←
Assuming 'n' is > 31
→
16
←
Taking false branch
→
80 hx = (hx<<n)|(lx>>(32-n));
81 lx <<= n;
82 } else {
83 hx = lx<<(n-32);
84 lx = 0;
85 }
86 }
87 if(iy >= -1022)
17
←
Assuming the condition is false
→
18
←
Taking false branch
→
88 hy = 0x00100000|(0x000fffff&hy);
89 else { /* subnormal y, shift y to normal */
90 n = -1022-iy;
91 if(n<=31) {
19
←
Assuming 'n' is > 31
→
20
←
Taking false branch
→
92 hy = (hy<<n)|(ly>>(32-n));
93 ly <<= n;
94 } else {
95 hy = ly<<(n-32);
96 ly = 0;
97 }
98 }
99
100 /* fix point fmod */
101 n = ix - iy;
102 q = 0;
103 while(n--) {
21
←
Loop condition is false. Execution continues on line 109
→
104 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
105 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
106 else {hx = hz+hz+(lz>>31); lx = lz+lz; q++;}
107 q <<= 1;
108 }
109 hz=hx-hy;lz=lx-ly; if(lx
21.1
'lx' is >= 'ly'
<ly) hz -= 1;
22
←
Taking false branch
→
110 if(hz>=0) {hx=hz;lx=lz;q++;}
23
←
Assuming 'hz' is < 0
→
24
←
Taking false branch
→
111
112 /* convert back to floating value and restore the sign */
113 if((hx|lx)==0) { /* return sign(x)*0 */
25
←
Assuming the condition is false
→
26
←
Taking false branch
→
114 *quo = (sxy ? -q : q);
115 return Zero[(u_int32_t)sx>>31];
116 }
117 while(hx<0x00100000) { /* normalize x */
27
←
Assuming 'hx' is < 1048576
→
28
←
Loop condition is true. Entering loop body
→
29
←
Assuming 'hx' is >= 1048576
→
30
←
Loop condition is false. Execution continues on line 121
→
118 hx = hx+hx+(lx>>31); lx = lx+lx;
119 iy -= 1;
120 }
121 if(iy>= -1022) { /* normalize output */
31
←
Assuming the condition is true
→
32
←
Taking true branch
→
122 hx = ((hx-0x00100000)|((iy+1023)<<20));
33
←
The result of the left shift is undefined because the left operand is negative
123 } else { /* subnormal output */
124 n = -1022 - iy;
125 if(n<=20) {
126 lx = (lx>>n)|((u_int32_t)hx<<(32-n));
127 hx >>= n;
128 } else if (n<=31) {
129 lx = (hx<<(32-n))|(lx>>n); hx = sx;
130 } else {
131 lx = hx>>(n-32); hx = sx;
132 }
133 }
134fixup:
135 INSERT_WORDS(x,hx,lx)do { ieee_double_shape_type iw_u; iw_u.parts.msw = (hx); iw_u
.parts.lsw = (lx); (x) = iw_u.value; } while (0);
136 y = fabs(y);
137 if (y < 0x1p-1021) {
138 if (x+x>y || (x+x==y && (q & 1))) {
139 q++;
140 x-=y;
141 }
142 } else if (x>0.5*y || (x==0.5*y && (q & 1))) {
143 q++;
144 x-=y;
145 }
146 GET_HIGH_WORD(hx,x)do { ieee_double_shape_type gh_u; gh_u.value = (x); (hx) = gh_u
.parts.msw; } while (0);
147 SET_HIGH_WORD(x,hx^sx)do { ieee_double_shape_type sh_u; sh_u.value = (x); sh_u.parts
.msw = (hx^sx); (x) = sh_u.value; } while (0);
148 q &= 0x7fffffff;
149 *quo = (sxy ? -q : q);
150 return x;
151}
152DEF_STD(remquo)__asm__(".global " "remquo" " ; " "remquo" " = " "_libm_remquo"
);
153LDBL_MAYBE_CLONE(remquo)__asm("");