On Mon, 28 Nov 2016, Richard Biener wrote:
>
> The following fixes an optimization regression noted in PR78546 where
> moving patterns from forwprop to match.pd missed one variant.
>
> Bootstrap & regtest running on x86_64-unknown-linux-gnu.
The following is what I have applied (note the fix, the transform
obviously need to transform to CST + A). I've adjusted surrounding
patterns to use different CST names in comments.
Richard.
2016-11-29 Richard Biener <rguent...@suse.de>
PR middle-end/78546
* match.pd: Add CST1 - (CST2 - A) -> CST3 + A missing case.
* gcc.dg/tree-ssa/forwprop-36.c: New testcase.
Index: gcc/match.pd
===================================================================
--- gcc/match.pd (revision 242952)
+++ gcc/match.pd (working copy)
@@ -1195,7 +1195,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(minus @0 (minus @0 @1))
@1)
- /* (A +- CST) +- CST -> A + CST */
+ /* (A +- CST1) +- CST2 -> A + CST3 */
(for outer_op (plus minus)
(for inner_op (plus minus)
(simplify
@@ -1208,7 +1208,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(if (cst && !TREE_OVERFLOW (cst))
(inner_op @0 { cst; } ))))))
- /* (CST - A) +- CST -> CST - A */
+ /* (CST1 - A) +- CST2 -> CST3 - A */
(for outer_op (plus minus)
(simplify
(outer_op (minus CONSTANT_CLASS_P@1 @0) CONSTANT_CLASS_P@2)
@@ -1216,6 +1216,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(if (cst && !TREE_OVERFLOW (cst))
(minus { cst; } @0)))))
+ /* CST1 - (CST2 - A) -> CST3 + A */
+ (simplify
+ (minus CONSTANT_CLASS_P@1 (minus CONSTANT_CLASS_P@2 @0))
+ (with { tree cst = const_binop (MINUS_EXPR, type, @1, @2); }
+ (if (cst && !TREE_OVERFLOW (cst))
+ (plus { cst; } @0))))
+
/* ~A + A -> -1 */
(simplify
(plus:c (bit_not @0) @0)
Index: gcc/testsuite/gcc.dg/tree-ssa/forwprop-36.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/forwprop-36.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/forwprop-36.c (working copy)
@@ -0,0 +1,24 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+typedef unsigned __int128 u128;
+
+u128 a, b;
+
+static inline u128
+foo (u128 p1)
+{
+ p1 += ~b;
+ return -p1;
+}
+
+int
+main ()
+{
+ u128 x = foo (~0x7fffffffffffffff);
+ if (x != 0x8000000000000001)
+ __builtin_abort();
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump "if \\(b.0_\[0-9\]+ != 0\\)" "cddce1" } } */
