On Thu, 25 Jan 2018, Richard Biener wrote:
> On Thu, 25 Jan 2018, Marc Glisse wrote:
>
> > On Thu, 25 Jan 2018, Richard Biener wrote:
> >
> > > --- gcc/match.pd (revision 257047)
> > > +++ gcc/match.pd (working copy)
> > > @@ -1939,6 +1939,37 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > > (minus (convert (view_convert:stype @1))
> > > (convert (view_convert:stype @2)))))))
> > >
> > > +/* (A * C) +- (B * C) -> (A+-B) * C and (A * C) +- A -> A * (C+-1).
> > > + Modeled after fold_plusminus_mult_expr. */
> > > +(if (!TYPE_SATURATING (type)
> > > + && (!FLOAT_TYPE_P (type) || flag_associative_math))
> > > + (for plusminus (plus minus)
> > > + (simplify
> > > + (plusminus (mult:s @0 @1) (mult:cs @0 @2))
> >
> > No :c on the first mult, so we don't actually handle A*C+B*C?
>
> Hmm, I somehow convinced myself that it's only necessary on one
> of the mults... but you are of course right. Will re-test with
> that fixed.
This is what I have applied. Note I had to XFAIL a minor part of
gcc.dg/tree-ssa/loop-15.c, namely simplifying the final value
replacement down to n * n. While the patch should enable this
the place where the transform could trigger with enough information
about n is VRP but that doesn't end up folding all stmts - and
that's something I'm not willing to change right now.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied on trunk.
Richard.
2018-01-26 Richard Biener <rguent...@suse.de>
PR tree-optimization/81082
* fold-const.c (fold_plusminus_mult_expr): Do not perform the
association if it requires casting to unsigned.
* match.pd ((A * C) +- (B * C) -> (A+-B)): New patterns derived
from fold_plusminus_mult_expr to catch important cases late when
range info is available.
* gcc.dg/vect/pr81082.c: New testcase.
* gcc.dg/tree-ssa/loop-15.c: XFAIL the (int)((unsigned)n + -1U) * n + n
simplification to n * n.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 257047)
+++ gcc/fold-const.c (working copy)
@@ -7097,7 +7097,7 @@ fold_plusminus_mult_expr (location_t loc
/* Same may be zero and thus the operation 'code' may overflow. Likewise
same may be minus one and thus the multiplication may overflow. Perform
- the operations in an unsigned type. */
+ the sum operation in an unsigned type. */
tree utype = unsigned_type_for (type);
tree tem = fold_build2_loc (loc, code, utype,
fold_convert_loc (loc, utype, alt0),
@@ -7110,9 +7110,9 @@ fold_plusminus_mult_expr (location_t loc
return fold_build2_loc (loc, MULT_EXPR, type,
fold_convert (type, tem), same);
- return fold_convert_loc (loc, type,
- fold_build2_loc (loc, MULT_EXPR, utype, tem,
- fold_convert_loc (loc, utype,
same)));
+ /* Do not resort to unsigned multiplication because
+ we lose the no-overflow property of the expression. */
+ return NULL_TREE;
}
/* Subroutine of native_encode_expr. Encode the INTEGER_CST
Index: gcc/match.pd
===================================================================
--- gcc/match.pd (revision 257047)
+++ gcc/match.pd (working copy)
@@ -1939,6 +1939,37 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(minus (convert (view_convert:stype @1))
(convert (view_convert:stype @2)))))))
+/* (A * C) +- (B * C) -> (A+-B) * C and (A * C) +- A -> A * (C+-1).
+ Modeled after fold_plusminus_mult_expr. */
+(if (!TYPE_SATURATING (type)
+ && (!FLOAT_TYPE_P (type) || flag_associative_math))
+ (for plusminus (plus minus)
+ (simplify
+ (plusminus (mult:cs @0 @1) (mult:cs @0 @2))
+ (if (!ANY_INTEGRAL_TYPE_P (type)
+ || TYPE_OVERFLOW_WRAPS (type)
+ || (INTEGRAL_TYPE_P (type)
+ && tree_expr_nonzero_p (@0)
+ && expr_not_equal_to (@0, wi::minus_one (TYPE_PRECISION (type)))))
+ (mult (plusminus @1 @2) @0)))
+ /* We cannot generate constant 1 for fract. */
+ (if (!ALL_FRACT_MODE_P (TYPE_MODE (type)))
+ (simplify
+ (plusminus @0 (mult:cs @0 @2))
+ (if (!ANY_INTEGRAL_TYPE_P (type)
+ || TYPE_OVERFLOW_WRAPS (type)
+ || (INTEGRAL_TYPE_P (type)
+ && tree_expr_nonzero_p (@0)
+ && expr_not_equal_to (@0, wi::minus_one (TYPE_PRECISION (type)))))
+ (mult (plusminus { build_one_cst (type); } @2) @0)))
+ (simplify
+ (plusminus (mult:cs @0 @2) @0)
+ (if (!ANY_INTEGRAL_TYPE_P (type)
+ || TYPE_OVERFLOW_WRAPS (type)
+ || (INTEGRAL_TYPE_P (type)
+ && tree_expr_nonzero_p (@0)
+ && expr_not_equal_to (@0, wi::minus_one (TYPE_PRECISION (type)))))
+ (mult (plusminus @2 { build_one_cst (type); }) @0))))))
/* Simplifications of MIN_EXPR, MAX_EXPR, fmin() and fmax(). */
Index: gcc/testsuite/gcc.dg/vect/pr81082.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/pr81082.c (revision 0)
+++ gcc/testsuite/gcc.dg/vect/pr81082.c (working copy)
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int } */
+
+int
+f (int *x, int b1, int b2, int b3)
+{
+ int foo = 0;
+ for (int i1 = 0; i1 < b1; ++i1)
+ for (int i2 = 0; i2 < b2; ++i2)
+ for (int i3 = 0; i3 < b3; ++i3)
+ foo += x[i1 * b2 * b3 + i2 * b3 + (i3 - 1)];
+ return foo;
+}
+
+/* { dg-final { scan-tree-dump "vectorized 1 loops in function" "vect" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/loop-15.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/loop-15.c (revision 257048)
+++ gcc/testsuite/gcc.dg/tree-ssa/loop-15.c (working copy)
@@ -19,7 +19,7 @@ int bla(void)
}
/* Since the loop is removed, there should be no addition. */
-/* { dg-final { scan-tree-dump-times " \\+ " 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " \\+ " 0 "optimized" { xfail *-*-* } } }
*/
/* { dg-final { scan-tree-dump-times " \\* " 1 "optimized" } } */
/* The if from the loop header copying remains in the code. */
