match.pd: Fix up 1 / X for unsigned X optimization [PR104280]

On Fri, Jan 28, 2022 at 11:38:23AM -0700, Jeff Law wrote:
> Thanks.  Given the original submission and most of the review work was done
> prior to stage3 closing, I went ahead and installed this on the trunk.

Unfortunately this breaks quite a lot of things.
The main problem is that GIMPLE allows EQ_EXPR etc. only with BOOLEAN_TYPE
or with TYPE_PRECISION == 1 integral type (or vector boolean).
Violating this causes verification failures in tree-cfg.cc in some cases,
in other cases wrong-code issues because before it is verified we e.g.
transform
1U / x
into
x == 1U
and later into
x (because we assume that == type must be one of the above cases and
when it is the same type as the type of the first operand, for boolean-ish
cases it should be equivalent).

Fixed by changing that
(eq @1 { build_one_cst (type); })
into
(convert (eq:boolean_type_node @1 { build_one_cst (type); }))
Note, I'm not 100% sure if :boolean_type_node is required in that case,
I see some spots in match.pd that look exactly like this, while there is
e.g. (convert (le ...)) that supposedly does the right thing too.
The signed integer 1/X case doesn't need changes changes, for
(cond (le ...) ...)
le gets correctly boolean_type_node and cond should use type.
I've also reformatted it, some lines were too long, match.pd uses
indentation by 1 column instead of 2 etc.

2022-01-29  Jakub Jelinek  <jakub@redhat.com>
	    Andrew Pinski  <apinski@marvell.com>

	PR tree-optimization/104279
	PR tree-optimization/104280
	PR tree-optimization/104281
	* match.pd (1 / X -> X == 1 for unsigned X): Build eq with
	boolean_type_node and convert to type.  Formatting fixes.

	* gcc.dg/torture/pr104279.c: New test.
	* gcc.dg/torture/pr104280.c: New test.
	* gcc.dg/torture/pr104281.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index 0544ddd..b942cb2 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -435,18 +435,22 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        && TYPE_UNSIGNED (type))
    (trunc_divmod @0 @1))))
 
- /* 1 / X -> X == 1 for unsigned integer X.
-    1 / X -> X >= -1 && X <= 1 ? X : 0 for signed integer X.
-    But not for 1 / 0 so that we can get proper warnings and errors,
-    and not for 1-bit integers as they are edge cases better handled elsewhere. */
-(simplify
-  (trunc_div integer_onep@0 @1)
-  (if (INTEGRAL_TYPE_P (type) && !integer_zerop (@1) && TYPE_PRECISION (type) > 1)
-    (if (TYPE_UNSIGNED (type))
-      (eq @1 { build_one_cst (type); })
-      (with { tree utype = unsigned_type_for (type); }
-        (cond (le (plus (convert:utype @1) { build_one_cst (utype); }) { build_int_cst (utype, 2); })
-          @1 { build_zero_cst (type); })))))
+/* 1 / X -> X == 1 for unsigned integer X.
+   1 / X -> X >= -1 && X <= 1 ? X : 0 for signed integer X.
+   But not for 1 / 0 so that we can get proper warnings and errors,
+   and not for 1-bit integers as they are edge cases better handled
+   elsewhere.  */
+(simplify
+ (trunc_div integer_onep@0 @1)
+ (if (INTEGRAL_TYPE_P (type)
+      && !integer_zerop (@1)
+      && TYPE_PRECISION (type) > 1)
+  (if (TYPE_UNSIGNED (type))
+   (convert (eq:boolean_type_node @1 { build_one_cst (type); }))
+   (with { tree utype = unsigned_type_for (type); }
+    (cond (le (plus (convert:utype @1) { build_one_cst (utype); })
+             { build_int_cst (utype, 2); })
+     @1 { build_zero_cst (type); })))))
 
 /* Combine two successive divisions.  Note that combining ceil_div
    and floor_div is trickier and combining round_div even more so.  */

diff --git a/gcc/testsuite/gcc.dg/torture/pr104279.c b/gcc/testsuite/gcc.dg/torture/pr104279.c
new file mode 100644 (file)
index 0000000..7c4fc20
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr104279.c
@@ -0,0 +1,12 @@
+/* PR tree-optimization/104279 */
+/* { dg-do compile } */
+
+unsigned a, b;
+
+int
+main ()
+{
+  b = ~(0 || ~0);
+  a = ~b / ~a;
+  return 0;
+}

diff --git a/gcc/testsuite/gcc.dg/torture/pr104280.c b/gcc/testsuite/gcc.dg/torture/pr104280.c
new file mode 100644 (file)
index 0000000..c5a1d9b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr104280.c
@@ -0,0 +1,16 @@
+/* PR tree-optimization/104280 */
+/* { dg-do run } */
+
+int
+foo (unsigned b, int c)
+{
+  return b / c;
+}
+
+int
+main ()
+{
+  if (foo (1, 2) != 0)
+    __builtin_abort ();
+  return 0;
+}

diff --git a/gcc/testsuite/gcc.dg/torture/pr104281.c b/gcc/testsuite/gcc.dg/torture/pr104281.c
new file mode 100644 (file)
index 0000000..35c8e20
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr104281.c
@@ -0,0 +1,22 @@
+/* PR tree-optimization/104281 */
+/* { dg-do run } */
+
+unsigned a = 1;
+int b, c = 2;
+long d;
+
+int
+main ()
+{
+  while (1)
+    {
+      int m = a;
+    L:
+      a = ~(-(m || b & d));
+      b = ((1 ^ a) / c);
+      if (b)
+       goto L;
+      break;
+    }
+  return 0;
+}