https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69377
Bug ID: 69377 Summary: wrong code at -O2 on x86_64-linux-gnu (in 32-bit mode) Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: su at cs dot ucdavis.edu Target Milestone: --- The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O2 in the 32-bit mode (but not in the 64-bit mode). This is a regression from 5.3.x. The reduced test is still fairly large; this has been a tough one to reduce. $ gcc-trunk -v Using built-in specs. COLLECT_GCC=gcc-trunk COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk --enable-languages=c,c++ --disable-werror --enable-multilib Thread model: posix gcc version 6.0.0 20160119 (experimental) [trunk revision 232571] (GCC) $ $ gcc-trunk -m32 -Os small.c; ./a.out 2 1 1 $ gcc-5.3 -m32 -O2 small.c; ./a.out 2 1 1 $ gcc-trunk -m32 -O2 small.c $ ./a.out 2 1 $ --------------------------------------------------- int printf (const char *, ...); int r, *s, t, p, a, q, b; short u = 3; static int *v; char c; static int * fn1 (int p1) { int w = 2, j; for (; q < 1;) { int d = 6094 ^ p, e = ~r; p = e; if (!d) return &t; j = 0; for (; j < 1;) { j = 0; for (; j < 1; j++) for (; q < 2; q++) ; } } if (u) for (;;) { char x; int y, z = 1, t1; x = 7; for (; x; x++) { int f = p || r; t1 = ~p | w; w = (u || f % a) % ~(t1 && f) - r; if (p < 6) { printf ("%d\n", t1); break; } } int g = 4 % w; if (g) { --p; int h = p && t1; z = h; if (p > 5 && z) continue; } y = g; if (z < p) { int i = g / u; y = i; } int j = u & y, k, o = z * x; if (p) { k = z; o = t1; c = x; z = -y; t1 = (j && y << c) + k || x; x = ~(u % p); if (x < c) printf ("%d\n", t1); } int l = p < z; short m = ((l && y) & ~u) * t1; int n = u && t1; if (t1 && x && (!x || z)) m = l * (y && n) | x; printf ("%d\n", t1); if (o && m > w) *v = 0; else { if (!p1) continue; return &b; } } } static void fn2 (char p1) { s = fn1 (254); for (; p1 <= 0;) { s = fn1 (254); for (;;) ; } } int main () { fn2 (4); return 0; }