diff options
Diffstat (limited to 'gcc/expr.c')
| -rw-r--r-- | gcc/expr.c | 41 |
1 files changed, 41 insertions, 0 deletions
@@ -62,6 +62,8 @@ along with GCC; see the file COPYING3. If not see #include "ccmp.h" #include "gimple-fold.h" #include "rtx-vector-builder.h" +#include "tree-pretty-print.h" +#include "flags.h" /* If this is nonzero, we do not bother generating VOLATILE @@ -12275,6 +12277,37 @@ maybe_optimize_mod_cmp (enum tree_code code, tree *arg0, tree *arg1) *arg1 = c4; return code == EQ_EXPR ? LE_EXPR : GT_EXPR; } + +/* Optimize x - y < 0 into x < 0 if x - y has undefined overflow. */ + +void +maybe_optimize_sub_cmp_0 (enum tree_code code, tree *arg0, tree *arg1) +{ + gcc_checking_assert (code == GT_EXPR || code == GE_EXPR + || code == LT_EXPR || code == LE_EXPR); + gcc_checking_assert (integer_zerop (*arg1)); + + if (!optimize) + return; + + gimple *stmt = get_def_for_expr (*arg0, MINUS_EXPR); + if (stmt == NULL) + return; + + tree treeop0 = gimple_assign_rhs1 (stmt); + tree treeop1 = gimple_assign_rhs2 (stmt); + if (!TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (treeop0))) + return; + + if (issue_strict_overflow_warning (WARN_STRICT_OVERFLOW_COMPARISON)) + warning_at (gimple_location (stmt), OPT_Wstrict_overflow, + "assuming signed overflow does not occur when " + "simplifying %<X - Y %s 0%> to %<X %s Y%>", + op_symbol_code (code), op_symbol_code (code)); + + *arg0 = treeop0; + *arg1 = treeop1; +} /* Generate code to calculate OPS, and exploded expression using a store-flag instruction and return an rtx for the result. @@ -12363,6 +12396,14 @@ do_store_flag (sepops ops, rtx target, machine_mode mode) } } + /* Optimize (x - y) < 0 into x < y if x - y has undefined overflow. */ + if (!unsignedp + && (ops->code == LT_EXPR || ops->code == LE_EXPR + || ops->code == GT_EXPR || ops->code == GE_EXPR) + && integer_zerop (arg1) + && TREE_CODE (arg0) == SSA_NAME) + maybe_optimize_sub_cmp_0 (ops->code, &arg0, &arg1); + /* Get the rtx comparison code to use. We know that EXP is a comparison operation of some type. Some comparisons against 1 and -1 can be converted to comparisons with zero. Do so here so that the tests |