As I believe I pointed out in a follow-up message, 254.gap is depending
on signed overflow semantics.
This patch avoids eliminating a cast feeding a conditional when the
SSA_NAME's range has overflowed unless -fstrict-overflow is in effect.
Thus 254.gap should be building with -fno-strict-overflow.
This patch also introduces a warning when the optimization is applied
and the ranges have overflowed.
Bootstrapped and regression tested on x86-unknown-linux-gnu.
OK for the trunk?
commit 62bbaa8de0e8d929eb3c63331b47950e9b09d801
Author: Jeff Law <l...@redhat.com>
Date: Wed May 1 12:33:20 2013 -0600
PR tree-optimization/57124
* tree-vrp.c (simplify_cond_using_ranges): Only simplify a
conversion feeding a condition if the range has an overflow
if -fstrict-overflow. Add warnings for when we do make the
transformation.
PR tree-optimization/57124
* gcc.c-torture/execute/pr57124.c: New test.
* gcc.c-torture/execute/pr57124.x: Set -fno-strict-overflow.
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8e92c44..9320f21 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2013-05-17 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/57124
+ * tree-vrp.c (simplify_cond_using_ranges): Only simplify a
+ conversion feeding a condition if the range has an overflow
+ if -fstrict-overflow. Add warnings for when we do make the
+ transformation.
+
2013-05-16 Rainer Orth <r...@cebitec.uni-bielefeld.de>
* reorg.c (link_cc0_insns): Wrap in #ifdef HAVE_cc0.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 879b9bc..482151c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2013-05-17 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/57124
+ * gcc.c-torture/execute/pr57124.c: New test.
+ * gcc.c-torture/execute/pr57124.x: Set -fno-strict-overflow.
+
2013-05-16 Greta Yorsh <greta.yo...@arm.com>
* gcc.target/arm/unaligned-memcpy-2.c: Adjust expected output.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr57124.c
b/gcc/testsuite/gcc.c-torture/execute/pr57124.c
new file mode 100644
index 0000000..835d249
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr57124.c
@@ -0,0 +1,27 @@
+__attribute__ ((noinline))
+foo(short unsigned int *p1, short unsigned int *p2)
+{
+ short unsigned int x1, x4;
+ int x2, x3, x5, x6;
+ unsigned int x7;
+
+ x1 = *p1;
+ x2 = (int) x1;
+ x3 = x2 * 65536;
+ x4 = *p2;
+ x5 = (int) x4;
+ x6 = x3 + x4;
+ x7 = (unsigned int) x6;
+ if (x7 <= 268435455U)
+ abort ();
+ exit (0);
+}
+
+main()
+{
+ short unsigned int x, y;
+ x = -5;
+ y = -10;
+ foo (&x, &y);
+}
+
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr57124.x
b/gcc/testsuite/gcc.c-torture/execute/pr57124.x
new file mode 100644
index 0000000..d8cacbe
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr57124.x
@@ -0,0 +1,2 @@
+set additional_flags "-fno-strict-overflow"
+return 0
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index b5de683..b3eccf0 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -8669,8 +8669,32 @@ simplify_cond_using_ranges (gimple stmt)
&& range_fits_type_p (vr,
TYPE_PRECISION (TREE_TYPE (op0)),
TYPE_UNSIGNED (TREE_TYPE (op0)))
- && int_fits_type_p (op1, TREE_TYPE (innerop)))
+ && int_fits_type_p (op1, TREE_TYPE (innerop))
+ /* The range must not have overflowed, or if it did overflow
+ we must not be wrapping/trapping overflow and optimizing
+ with strict overflow semantics. */
+ && ((!is_negative_overflow_infinity (vr->min)
+ && !is_positive_overflow_infinity (vr->max))
+ || (!flag_wrapv && !flag_trapv && flag_strict_overflow)))
{
+ /* If the range overflowed and the user has asked for warnings
+ when strict overflow semantics were used to optimize code,
+ issue an appropriate warning. */
+ if ((is_negative_overflow_infinity (vr->min)
+ || is_positive_overflow_infinity (vr->max))
+ && issue_strict_overflow_warning
(WARN_STRICT_OVERFLOW_CONDITIONAL))
+ {
+ location_t location;
+
+ if (!gimple_has_location (stmt))
+ location = input_location;
+ else
+ location = gimple_location (stmt);
+ warning_at (location, OPT_Wstrict_overflow,
+ "assuming signed overflow does not occur when "
+ "simplifying conditional.");
+ }
+
tree newconst = fold_convert (TREE_TYPE (innerop), op1);
gimple_cond_set_lhs (stmt, innerop);
gimple_cond_set_rhs (stmt, newconst);
