On Fri, Dec 15, 2017 at 10:28:52AM +0100, Richard Biener wrote:
> > --- 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))))
>
> Given @1 and @@0 are in the same plus this change isn't technically
> necessary but it makes it clearer which type we look at (thus ok).
My understanding is that it is necessary, because @@0 could have different
type from @0 and TREE_TYPE (@0) is the type of where @0 is used rather
than @@0.
> > (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)))))
>
> I think we don't need to worry about definedness of overflow. All
We are talking about
(int) (x + 0x80000000U) + INT_MIN
I think you're right that we can still optimize that to (int) x.
> that matters is whether twos complement arithmetic will simplify
> the expression to (convert @1). Specifically the possible overflow
> of the negation of @2 for the case element_precision (type) <=
> element_precision (TREE_TYPE (@1)) shouldn't matter, likewise
> for the widening case (we'd never get the equality).
>
> Don't we want to compare @0 and -@2 in the type of @2? Like
> for (unsigned int)(unsigned-long-x + 0x100000005) + -5U which
> we should be able to simplify? For the widening case that would
> work as well as far as I can see?
So, we can have several cases, the narrowing one, e.g.:
(int)(unsigned-long-long-x + 0x100000005ULL) + -5
(unsigned)(long-long-x + 0x100000005LL) + -5U
(int)(unsigned-long-long-x + 0x1fffffffbULL) + 5
(unsigned)(long-long-x + 0x1fffffffbLL) + 5U
same precision:
(int)(unsigned-x + 5U) + -5
(unsigned)(int-x + 5) + -5U
(int)(unsigned-x + -5U) + 5
(unsigned)(int-x + -5) + 5
and widening ones:
(long long)(int-x + 5) + -5LL
(unsigned long long)(int-x + 5) + -5ULL
(long long)(int-x + -5) + 5LL
(unsigned long long)(int-x + -5) + 5ULL
You mean we should effectively (though on wide_int/widest_int)
fold_unary (MINUS_EXPR, TREE_TYPE (@2), fold_convert (TREE_TYPE (@2), @0))
and compare that to @2?
> If you can split out this new pattern the rest is ok with honoring
> the comment below.
Ok (will need to comment out the corresponding testcase, done below).
> > - || (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))))
Yeah, this @1 above should have been @2. Thanks for catching this.
So for now like this?
2017-12-15 Jakub Jelinek <ja...@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.
((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 18:04:54.580750329 +0100
+++ gcc/match.pd 2017-12-15 11:52:22.582118364 +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
@@ -1794,8 +1794,8 @@ 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))))
(convert @1)))
(simplify
(minus (convert (pointer_plus @@0 @1))
@@ -1818,8 +1818,8 @@ 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 +1833,8 @@ 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 +1862,28 @@ 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 (@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))
+ && 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 2017-12-15 11:51:38.294654394 +0100
+++ gcc/testsuite/gcc.dg/pr81281-3.c 2017-12-15 11:56:08.097388860 +0100
@@ -0,0 +1,105 @@
+/* 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;
+}
+
+/* This isn't optimized yet. */
+#if 0
+long long
+f5 (int a)
+{
+ long long f = 123 + a;
+ long long g = 123;
+ return f - g;
+}
+#endif
+
+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
