[PATCH] Further improvements for the (T)(P+A)-(T)(P+B) folding (PR sanitizer/81281)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

When committing the previous PR81281 patch, I've removed all the @@0 cases
on plus:c, used @0 instead, to make sure we don't regress.

This patch readds those where possible.  For the cases where there is
just P and A, it was mostly a matter of @@0 and convert? instead of convert
plus using type from @1 instead of @0, though if @0 is INTEGER_CST, what we
usually end up with is a (plus (convert (plus @1 @0) @2) where @2 negated
is equal to @0, so the patch adds a simplification for that too.

For the case with P, A and B, the patch limits it to the case where either
both A and B are narrower or both are wider.

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

2017-12-07  Jakub Jelinek  <jakub@redhat.com>

	PR sanitizer/81281
	* match.pd ((T)(P + A) - (T)P -> (T) A): Use @@0 instead of @0 and
	convert? on @0 instead of convert.  Check type of @1, not @0.
	Add a simplify for (T)(P + A) + Q where -Q is equal to P.
	((T)P - (T)(P + A) -> -(T) A): Use @@0 instead of @0 and
	convert? on @0 instead of convert.  Check type of @1, not @0.
	((T)(P + A) - (T)(P + B) -> (T)A - (T)B): Use @@0 instead of @0,
	only optimize if either both @1 and @2 types are narrower
	precision, or both are wider or equal precision, and in the former
	case only if both have undefined overflow.

	* gcc.dg/pr81281-3.c: New test.

--- gcc/match.pd.jj	2017-12-07 14:00:51.083048186 +0100
+++ gcc/match.pd	2017-12-07 15:17:49.132784931 +0100
@@ -1784,8 +1784,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
   /* (T)(P + A) - (T)P -> (T) A */
   (simplify
-   (minus (convert (plus:c @0 @1))
-    (convert @0))
+   (minus (convert (plus:c @@0 @1))
+    (convert? @0))
    (if (element_precision (type) <= element_precision (TREE_TYPE (@1))
 	/* For integer types, if A has a smaller type
 	   than T the result depends on the possible
@@ -1794,10 +1794,29 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	   However, if an overflow in P + A would cause
 	   undefined behavior, we can assume that there
 	   is no overflow.  */
-	|| (INTEGRAL_TYPE_P (TREE_TYPE (@0))
-	    && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))))
+	|| (INTEGRAL_TYPE_P (TREE_TYPE (@1))
+	    && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1))))
     (convert @1)))
   (simplify
+   (plus (convert (plus @1 INTEGER_CST@0)) INTEGER_CST@2)
+   (with { bool overflow;
+	   wide_int w = wi::neg (wi::to_wide (@2), &overflow); }
+    (if (wi::to_widest (@0) == widest_int::from (w, TYPE_SIGN (TREE_TYPE (@2)))
+	 && (!overflow
+	     || (INTEGRAL_TYPE_P (TREE_TYPE (@2))
+		 && TYPE_UNSIGNED (TREE_TYPE (@2))))
+	 && (element_precision (type) <= element_precision (TREE_TYPE (@1))
+	     /* For integer types, if A has a smaller type
+		than T the result depends on the possible
+		overflow in P + A.
+		E.g. T=size_t, A=(unsigned)429497295, P>0.
+		However, if an overflow in P + A would cause
+		undefined behavior, we can assume that there
+		is no overflow.  */
+	     || (INTEGRAL_TYPE_P (TREE_TYPE (@1))
+		 && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1)))))
+     (convert @1))))
+  (simplify
    (minus (convert (pointer_plus @@0 @1))
     (convert @0))
    (if (element_precision (type) <= element_precision (TREE_TYPE (@1))
@@ -1818,8 +1837,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
   /* (T)P - (T)(P + A) -> -(T) A */
   (simplify
-   (minus (convert @0)
-    (convert (plus:c @0 @1)))
+   (minus (convert? @0)
+    (convert (plus:c @@0 @1)))
    (if (INTEGRAL_TYPE_P (type)
 	&& TYPE_OVERFLOW_UNDEFINED (type)
 	&& element_precision (type) <= element_precision (TREE_TYPE (@1)))
@@ -1833,8 +1852,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	    However, if an overflow in P + A would cause
 	    undefined behavior, we can assume that there
 	    is no overflow.  */
-	 || (INTEGRAL_TYPE_P (TREE_TYPE (@0))
-	     && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))))
+	 || (INTEGRAL_TYPE_P (TREE_TYPE (@1))
+	     && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1))))
      (negate (convert @1)))))
   (simplify
    (minus (convert @0)
@@ -1862,23 +1881,28 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
   /* (T)(P + A) - (T)(P + B) -> (T)A - (T)B */
   (simplify
-   (minus (convert (plus:c @0 @1))
+   (minus (convert (plus:c @@0 @1))
     (convert (plus:c @0 @2)))
    (if (INTEGRAL_TYPE_P (type)
 	&& TYPE_OVERFLOW_UNDEFINED (type)
-	&& element_precision (type) <= element_precision (TREE_TYPE (@1)))
+	&& element_precision (type) <= element_precision (TREE_TYPE (@1))
+	&& element_precision (type) <= element_precision (TREE_TYPE (@2)))
     (with { tree utype = unsigned_type_for (type); }
      (convert (minus (convert:utype @1) (convert:utype @2))))
-    (if (element_precision (type) <= element_precision (TREE_TYPE (@1))
-	 /* For integer types, if A has a smaller type
-	    than T the result depends on the possible
-	    overflow in P + A.
-	    E.g. T=size_t, A=(unsigned)429497295, P>0.
-	    However, if an overflow in P + A would cause
-	    undefined behavior, we can assume that there
-	    is no overflow.  */
-	 || (INTEGRAL_TYPE_P (TREE_TYPE (@0))
-	     && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))))
+    (if (((element_precision (type) <= element_precision (TREE_TYPE (@1)))
+	  == (element_precision (type) <= element_precision (TREE_TYPE (@1))))
+	 && (element_precision (type) <= element_precision (TREE_TYPE (@1))
+	     /* For integer types, if A has a smaller type
+		than T the result depends on the possible
+		overflow in P + A.
+		E.g. T=size_t, A=(unsigned)429497295, P>0.
+		However, if an overflow in P + A would cause
+		undefined behavior, we can assume that there
+		is no overflow.  */
+	     || (INTEGRAL_TYPE_P (TREE_TYPE (@1))
+		 && INTEGRAL_TYPE_P (TREE_TYPE (@2))
+		 && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1))
+		 && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@2)))))
      (minus (convert @1) (convert @2)))))
   (simplify
    (minus (convert (pointer_plus @@0 @1))
--- gcc/testsuite/gcc.dg/pr81281-3.c.jj	2017-12-07 15:19:06.334840988 +0100
+++ gcc/testsuite/gcc.dg/pr81281-3.c	2017-12-07 14:38:25.000000000 +0100
@@ -0,0 +1,102 @@
+/* PR sanitizer/81281 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-not "\[+=-] \?123\[ ;]" "optimized" } } */
+
+#ifdef __SIZEOF_INT128__
+__int128
+f1 (int a, long long b)
+{
+  __int128 f = 123 + a;
+  __int128 g = 123 + b;
+  return f - g;
+}
+#endif
+
+signed char
+f2 (int a, long long b)
+{
+  signed char f = 123 + a;
+  signed char g = 123 + b;
+  return f - g;
+}
+
+signed char
+f3 (unsigned int a, unsigned long long b)
+{
+  signed char f = 123 + a;
+  signed char g = 123 + b;
+  return f - g;
+}
+
+unsigned char
+f4 (unsigned int a, unsigned long long b)
+{
+  unsigned char f = 123 + a;
+  unsigned char g = 123 + b;
+  return f - g;
+}
+
+long long
+f5 (int a)
+{
+  long long f = 123 + a;
+  long long g = 123;
+  return f - g;
+}
+
+signed char
+f6 (long long a)
+{
+  signed char f = 123 + a;
+  signed char g = 123;
+  return f - g;
+}
+
+signed char
+f7 (unsigned int a)
+{
+  signed char f = 123 + a;
+  signed char g = 123;
+  return f - g;
+}
+
+unsigned char
+f8 (unsigned long int a)
+{
+  unsigned char f = 123 + a;
+  unsigned char g = 123;
+  return f - g;
+}
+
+long long
+f9 (int a)
+{
+  long long f = 123;
+  long long g = 123 + a;
+  return f - g;
+}
+
+signed char
+f10 (long long a)
+{
+  signed char f = 123;
+  signed char g = 123 + a;
+  return f - g;
+}
+
+signed char
+f11 (unsigned int a)
+{
+  signed char f = 123;
+  signed char g = 123 + a;
+  return f - g;
+}
+
+unsigned char
+f12 (unsigned long int a)
+{
+  unsigned char f = 123;
+  unsigned char g = 123 + a;
+  return f - g;
+}

	Jakub