On December 13, 2020 12:02:48 PM GMT+01:00, Jakub Jelinek <[email protected]> wrote: >Hi! > >Unfortunately, my latest tree-ssa-math-opts.c patch broke the following >testcase. The problem is that the code is adding .ADD_OVERFLOW or >.SUB_OVERFLOW before or after the stmt on which the function has been >called, which is normally a addition or subtraction that has all the >operands. >But in the a > ~b optimization that stmt is the ~b stmt and the other >comparison operand might be defined only after that ~b stmt, so we >can't >insert the .ADD_OVERFLOW next to ~b that we want to delete, but need to >insert it before the a > temp comparison that uses it; and in that case >when removing the BIT_NOT_EXPR stmt we need to ensure the caller >doesn't do >gsi_next because gsi_remove already points the iterator to the next >stmt. > >Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok. Richard. >2020-12-13 Jakub Jelinek <[email protected]> > > PR tree-optimization/98256 > * tree-ssa-math-opts.c (match_uaddsub_overflow): For BIT_NOT_EXPR, > only handle a single use, and insert .ADD_OVERFLOW before the > comparison rather than after the BIT_NOT_EXPR. Return true iff > it is BIT_NOT_EXPR and it has been removed. > (math_opts_dom_walker::after_dom_children) <case BIT_NOT_EXPR>: > If match_uaddsub_overflow returned true, continue instead of break. > > * gcc.c-torture/compile/pr98256.c: New test. > >--- gcc/tree-ssa-math-opts.c.jj 2020-12-12 14:48:40.195306781 +0100 >+++ gcc/tree-ssa-math-opts.c 2020-12-12 22:42:24.474396562 +0100 >@@ -3598,6 +3598,7 @@ match_uaddsub_overflow (gimple_stmt_iter > gimple *use_stmt; > gimple *add_stmt = NULL; > bool add_first = false; >+ gimple *cond_stmt = NULL; > > gcc_checking_assert (code == PLUS_EXPR > || code == MINUS_EXPR >@@ -3628,8 +3629,9 @@ match_uaddsub_overflow (gimple_stmt_iter > return false; > if (rhs2 == NULL) > rhs2 = other; >- else if (rhs2 != other) >+ else > return false; >+ cond_stmt = use_stmt; > } > ovf_use_seen = true; > } >@@ -3818,6 +3820,9 @@ match_uaddsub_overflow (gimple_stmt_iter > } > } > >+ if (code == BIT_NOT_EXPR) >+ *gsi = gsi_for_stmt (cond_stmt); >+ > tree ctype = build_complex_type (type); > gcall *g = gimple_build_call_internal (code != MINUS_EXPR > ? IFN_ADD_OVERFLOW : IFN_SUB_OVERFLOW, >@@ -3843,7 +3848,10 @@ match_uaddsub_overflow (gimple_stmt_iter > tree ovf = make_ssa_name (type); > g2 = gimple_build_assign (ovf, IMAGPART_EXPR, > build1 (IMAGPART_EXPR, type, ctmp)); >- gsi_insert_after (gsi, g2, GSI_NEW_STMT); >+ if (code != BIT_NOT_EXPR) >+ gsi_insert_after (gsi, g2, GSI_NEW_STMT); >+ else >+ gsi_insert_before (gsi, g2, GSI_SAME_STMT); > > FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs) > { >@@ -3908,11 +3916,12 @@ match_uaddsub_overflow (gimple_stmt_iter > } > else if (code == BIT_NOT_EXPR) > { >- gimple_stmt_iterator gsi2 = gsi_for_stmt (stmt); >- gsi_remove (&gsi2, true); >+ *gsi = gsi_for_stmt (stmt); >+ gsi_remove (gsi, true); > release_ssa_name (lhs); >+ return true; > } >- return true; >+ return false; > } > > /* Return true if target has support for divmod. */ >@@ -4238,7 +4247,8 @@ math_opts_dom_walker::after_dom_children > break; > > case BIT_NOT_EXPR: >- match_uaddsub_overflow (&gsi, stmt, code); >+ if (match_uaddsub_overflow (&gsi, stmt, code)) >+ continue; > break; > > case TRUNC_MOD_EXPR: >--- gcc/testsuite/gcc.c-torture/compile/pr98256.c.jj 2020-12-12 >22:44:34.037940761 +0100 >+++ gcc/testsuite/gcc.c-torture/compile/pr98256.c 2020-12-12 >22:35:54.452778912 +0100 >@@ -0,0 +1,9 @@ >+/* PR tree-optimization/98256 */ >+ >+unsigned a, b; >+ >+int >+foo (void) >+{ >+ return !!(~a / b); >+} > > Jakub
