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[PATCH] Fix match.pd narrowing opt (PR tree-optimization/66187)


Hi!

As the testcases show, for signed types we really should use SIGNED rather
than UNSIGNED as tree_int_cst_min_precision argument, that function doesn't
really do the desired thing with UNSIGNED for negative values and with
-fwrapv we just want the narrowing cast to not lose anything from the
number.  Additionally, as for TYPE_OVERFLOW_WRAPS case we perform the +/-/& in
unsigned type,  we have to avoid all negative masks, because those surely
have the higher bits set.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

For plus and unsigned type, we could improve it even further, as in that
case we could just check if the bit immediately above precision is clear
in the mask, higher bits than that are uninteresting, because the addition
will have always zeros there.  Perhaps as a follow-up?
I mean say uchar foo (uchar a, uchar b) { return (x + y) & 0x72fe; }
can be done as uchar addition & 0xfe, but not e.g. & 0x71fe.

2015-05-18  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/66187
	* match.pd ((bit_and (plus/minus (convert @0) (convert @1)) mask)):
	Pass TYPE_SIGN to tree_int_cst_min_precision.  If
	!TYPE_OVERFLOW_WRAPS, ensure @4 is non-negative.

	* gcc.c-torture/execute/pr66187.c: New test.
	* gcc.dg/pr66187-1.c: New test.
	* gcc.dg/pr66187-2.c: New test.

--- gcc/match.pd.jj	2015-05-18 09:46:39.000000000 +0200
+++ gcc/match.pd	2015-05-18 10:20:24.944475737 +0200
@@ -1115,8 +1115,10 @@ (define_operator_list CBRT BUILT_IN_CBRT
 	 /* The inner conversion must be a widening conversion.  */
 	 && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (TREE_TYPE (@0))
 	 && types_match (@0, @1)
-	 && (tree_int_cst_min_precision (@4, UNSIGNED)
+	 && (tree_int_cst_min_precision (@4, TYPE_SIGN (TREE_TYPE (@0)))
 	     <= TYPE_PRECISION (TREE_TYPE (@0)))
+	 && (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0))
+	     || tree_int_cst_sgn (@4) >= 0)
 	 && single_use (@5))
       (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
 	(with { tree ntype = TREE_TYPE (@0); }
--- gcc/testsuite/gcc.c-torture/execute/pr66187.c.jj	2015-05-18 10:53:43.953654893 +0200
+++ gcc/testsuite/gcc.c-torture/execute/pr66187.c	2015-05-18 10:53:28.000000000 +0200
@@ -0,0 +1,16 @@
+/* PR tree-optimization/66187 */
+
+int a = 1, e = -1;
+short b, f;
+
+int
+main ()
+{
+  f = e;
+  int g = b < 0 ? 0 : f + b;
+  if ((g & -4) < 0)
+    a = 0;
+  if (a)
+    __builtin_abort ();
+  return 0;
+}
--- gcc/testsuite/gcc.dg/pr66187-1.c.jj	2015-05-18 10:54:30.677906029 +0200
+++ gcc/testsuite/gcc.dg/pr66187-1.c	2015-05-18 12:30:17.000000000 +0200
@@ -0,0 +1,97 @@
+/* PR tree-optimization/66187 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-wrapv" } */
+
+__attribute__((noinline, noclone)) int
+f0 (unsigned char x, unsigned char y)
+{
+  return (x + y) & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f1 (unsigned char x, unsigned char y)
+{
+  return (x - y) & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f2 (signed char x, signed char y)
+{
+  return (x + y) & -4;
+}
+
+__attribute__((noinline, noclone)) int
+f3 (signed char x, signed char y)
+{
+  return (x + y) & 0xf8;
+}
+
+__attribute__((noinline, noclone)) int
+f4 (signed char x, signed char y)
+{
+  return (x + y) & 0x78;
+}
+
+__attribute__((noinline, noclone)) int
+f5 (unsigned char x, unsigned char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f6 (unsigned char x, unsigned char y)
+{
+  int a = x;
+  int b = y;
+  int c = a - b;
+  return c & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f7 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & -4;
+}
+
+__attribute__((noinline, noclone)) int
+f8 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0xf8;
+}
+
+__attribute__((noinline, noclone)) int
+f9 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0x78;
+}
+
+int
+main ()
+{
+  if (__SCHAR_MAX__ != 127 || sizeof (int) != 4)
+    return 0;
+  if (f0 (0xff, 0xff) != 0xfe
+      || f1 (0, 1) != 0x2ff
+      || f2 (-2, 1) != -4
+      || f3 (-2, 1) != 0xf8
+      || f4 (-2, 1) != 0x78
+      || f5 (0xff, 0xff) != 0xfe
+      || f6 (0, 1) != 0x2ff
+      || f7 (-2, 1) != -4
+      || f8 (-2, 1) != 0xf8
+      || f9 (-2, 1) != 0x78)
+    __builtin_abort ();
+  return 0;
+}
--- gcc/testsuite/gcc.dg/pr66187-2.c.jj	2015-05-18 12:31:39.398176973 +0200
+++ gcc/testsuite/gcc.dg/pr66187-2.c	2015-05-18 12:31:46.319067151 +0200
@@ -0,0 +1,97 @@
+/* PR tree-optimization/66187 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fwrapv" } */
+
+__attribute__((noinline, noclone)) int
+f0 (unsigned char x, unsigned char y)
+{
+  return (x + y) & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f1 (unsigned char x, unsigned char y)
+{
+  return (x - y) & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f2 (signed char x, signed char y)
+{
+  return (x + y) & -4;
+}
+
+__attribute__((noinline, noclone)) int
+f3 (signed char x, signed char y)
+{
+  return (x + y) & 0xf8;
+}
+
+__attribute__((noinline, noclone)) int
+f4 (signed char x, signed char y)
+{
+  return (x + y) & 0x78;
+}
+
+__attribute__((noinline, noclone)) int
+f5 (unsigned char x, unsigned char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f6 (unsigned char x, unsigned char y)
+{
+  int a = x;
+  int b = y;
+  int c = a - b;
+  return c & 0x2ff;
+}
+
+__attribute__((noinline, noclone)) int
+f7 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & -4;
+}
+
+__attribute__((noinline, noclone)) int
+f8 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0xf8;
+}
+
+__attribute__((noinline, noclone)) int
+f9 (signed char x, signed char y)
+{
+  int a = x;
+  int b = y;
+  int c = a + b;
+  return c & 0x78;
+}
+
+int
+main ()
+{
+  if (__SCHAR_MAX__ != 127 || sizeof (int) != 4)
+    return 0;
+  if (f0 (0xff, 0xff) != 0xfe
+      || f1 (0, 1) != 0x2ff
+      || f2 (-2, 1) != -4
+      || f3 (-2, 1) != 0xf8
+      || f4 (-2, 1) != 0x78
+      || f5 (0xff, 0xff) != 0xfe
+      || f6 (0, 1) != 0x2ff
+      || f7 (-2, 1) != -4
+      || f8 (-2, 1) != 0xf8
+      || f9 (-2, 1) != 0x78)
+    __builtin_abort ();
+  return 0;
+}

	Jakub


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