Hi! expand_omp_for_init_counts was using for the case where collapse(2) inner loop has init expression dependent on non-constant multiple of the outer iterator and the condition upper bound expression doesn't depend on the outer iterator fold_unary (NEGATE_EXPR, ...). This will just return NULL if it can't be folded, we need fold_build1 instead.
Bootstrapped/regtested on x86_64-linux and i686-linux, committed to trunk. 2023-01-19 Jakub Jelinek <ja...@redhat.com> PR middle-end/108459 * omp-expand.cc (expand_omp_for_init_counts): Use fold_build1 rather than fold_unary for NEGATE_EXPR. * testsuite/libgomp.c/pr108459.c: New test. --- gcc/omp-expand.cc.jj 2023-01-02 09:32:49.399894958 +0100 +++ gcc/omp-expand.cc 2023-01-19 12:01:05.103410564 +0100 @@ -2003,8 +2003,8 @@ expand_omp_for_init_counts (struct omp_f t = fold_build2 (MINUS_EXPR, itype, unshare_expr (fd->loops[i].m2), unshare_expr (fd->loops[i].m1)); else if (fd->loops[i].m1) - t = fold_unary (NEGATE_EXPR, itype, - unshare_expr (fd->loops[i].m1)); + t = fold_build1 (NEGATE_EXPR, itype, + unshare_expr (fd->loops[i].m1)); else t = unshare_expr (fd->loops[i].m2); tree m2minusm1 --- libgomp/testsuite/libgomp.c/pr108459.c.jj 2023-01-19 12:22:07.191038771 +0100 +++ libgomp/testsuite/libgomp.c/pr108459.c 2023-01-19 12:21:17.973755215 +0100 @@ -0,0 +1,41 @@ +/* PR middle-end/108459 */ + +char a[17][17]; + +__attribute__((noipa)) void +foo (int x, int y) +{ + #pragma omp for collapse(2) + for (int i = 1; i <= 16; i++) + for (int j = i * x + y; j <= 16; j++) + a[i][j] = 1; +} + +int +main () +{ + #pragma omp parallel + foo (1, 1); + for (int i = 0; i <= 16; i++) + for (int j = 0; j <= 16; j++) + if (i >= 1 && j >= i + 1) + { + if (a[i][j] != 1) + __builtin_abort (); + a[i][j] = 0; + } + else if (a[i][j]) + __builtin_abort (); + #pragma omp parallel + foo (2, -2); + for (int i = 0; i <= 16; i++) + for (int j = 0; j <= 16; j++) + if (i >= 1 && j >= 2 * i - 2) + { + if (a[i][j] != 1) + __builtin_abort (); + } + else if (a[i][j]) + __builtin_abort (); + return 0; +} Jakub