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* [PATCH] MATCH: remove negate for 1bit types
@ 2023-08-24  2:38 Andrew Pinski
  2023-08-24  6:40 ` Richard Biener
  0 siblings, 1 reply; 2+ messages in thread
From: Andrew Pinski @ 2023-08-24  2:38 UTC (permalink / raw)
  To: gcc-patches; +Cc: Andrew Pinski

For 1bit types, negate is either undefined or don't change the value.
In either cases we want to remove them.
This patch adds a match pattern to do that.
Also converting to a 1bit type we can remove the negate just like we already do
for `&1` so this patch adds that too.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Notes on the testcases:
This patch is the last part to fix PR 95929; cond-bool-2.c testcase.
bit1neg-1.c is a 1bit-field testcase where we could remove the assignment
all the way in one case (which happened on the RTL level for some targets but not all).
cond-bool-2.c is the reduced testcase of PR 95929.

	PR tree-optimization/95929

gcc/ChangeLog:

	* match.pd (convert?(-a)): New pattern
	for 1bit integer types.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/bit1neg-1.c: New test.
	* gcc.dg/tree-ssa/cond-bool-1.c: New test.
	* gcc.dg/tree-ssa/cond-bool-2.c: New test.
---
 gcc/match.pd                                | 12 ++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c   | 23 ++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c | 21 +++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c | 26 +++++++++++++++++++++
 4 files changed, 82 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c

diff --git a/gcc/match.pd b/gcc/match.pd
index a2e56d5a4e8..3bbeceb37b4 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -9090,6 +9090,18 @@ and,
  (if (!TYPE_OVERFLOW_SANITIZED (type))
   (bit_and @0 @1)))
 
+/* `-a` is just `a` if the type is 1bit wide or when converting
+   to a 1bit type; similar to the above transformation of `(-x)&1`.
+   This is used mostly with the transformation of
+   `a ? ~b : b` into `(-a)^b`.
+   It also can show up with bitfields.  */
+(simplify
+ (convert? (negate @0))
+ (if (INTEGRAL_TYPE_P (type)
+      && TYPE_PRECISION (type) == 1
+      && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0)))
+  (convert @0)))
+
 /* Optimize
    c1 = VEC_PERM_EXPR (a, a, mask)
    c2 = VEC_PERM_EXPR (b, b, mask)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c b/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
new file mode 100644
index 00000000000..2f123fbb9b5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/bit1neg-1.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+struct f
+{
+  int a:1;
+};
+
+void g(struct f *a)
+{
+ int t = a->a;
+ t = -t;
+ a->a = t;
+}
+void g1(struct f *a, int b)
+{
+ int t = b;
+ t = -t;
+ a->a = t;
+}
+/* the 2 negates should have been removed as this is basically the same
+   as (-a) & 1. */
+/* { dg-final { scan-tree-dump-not " = -" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
new file mode 100644
index 00000000000..752a3030ad1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-1.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
+_Bool f1(int a, int b)
+{
+  _Bool _1 = b != 0;
+  _Bool _2 = a != 0;
+  _Bool _8 = a == 0;
+  _Bool _13;
+  if (_1) _13 = _8; else _13 = _2;
+  return _13;
+}
+
+/* We should be able to optimize this to (a != 0) ^ (b != 0) */
+/* There should be no negate_expr nor gimple_cond here. */
+
+/* { dg-final { scan-tree-dump-not "negate_expr, " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "ne_expr, " 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-not "gimple_cond " "optimized" } } */
+/* { dg-final { scan-tree-dump-not "gimple_phi " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "bit_xor_expr, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "gimple_assign " 3 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
new file mode 100644
index 00000000000..b3e7e25dec6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cond-bool-2.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
+
+/* PR tree-optimization/95929 */
+
+
+static inline _Bool nand(_Bool a, _Bool b)
+{
+    return !(a && b);
+}
+
+_Bool f(int a, int b)
+{
+    return nand(nand(b, nand(a, a)), nand(a, nand(b, b)));
+}
+
+/* We should be able to optimize this to (a != 0) ^ (b != 0) */
+/* There should be no negate_expr nor gimple_cond here. */
+
+/* { dg-final { scan-tree-dump-not "negate_expr, " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "ne_expr, " 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-not "gimple_cond " "optimized" } } */
+/* { dg-final { scan-tree-dump-not "cond_expr, " "optimized" } } */
+/* { dg-final { scan-tree-dump-not "gimple_phi " "optimized" } } */
+/* { dg-final { scan-tree-dump-times "bit_xor_expr, " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "gimple_assign " 3 "optimized" } } */
-- 
2.31.1


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