match: Fix A || B not optimized to true when !B implies A [PR114326]

In expressions like (a != b || ((a ^ b) & c) == d) and
(a != b || (a ^ b) == c), (a ^ b) is folded to false.
In the equivalent expressions (((a ^ b) & c) == d || a != b) and
((a ^ b) == c || a != b) this is not happening.

This patch adds the following simplifications in match.pd:
((a ^ b) & c) cmp d || a != b --> 0 cmp d || a != b
(a ^ b) cmp c || a != b --> 0 cmp c || a != b

	PR tree-optimization/114326

gcc/ChangeLog:

	* match.pd: Add two patterns to fold a ^ b to 0, when a == b.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/fold-xor-and-or.c: New test.
	* gcc.dg/tree-ssa/fold-xor-or.c: New test.

Tested-by: Christoph Müllner <christoph.muellner@vrull.eu>
Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Signed-off-by: Konstantinos Eleftheriou <konstantinos.eleftheriou@vrull.eu>

diff --git a/gcc/match.pd b/gcc/match.pd
index 7150b8e78cab3cbc6a1d8372a4e61467cb8cb551..d10ac7d6cd20730501b3d6648e08f4a97dffc6c3 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3787,6 +3787,36 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
     (if (types_match (type, TREE_TYPE (@0)))
      (bit_xor @0 { build_one_cst (type); } ))))))
 
+/* ((a ^ b) & c) cmp d || a != b --> (0 cmp d || a != b). */
+(for cmp (simple_comparison)
+  (simplify
+    (bit_ior
+      (cmp:c
+       (bit_and:c
+         (bit_xor:c @0 @1)
+         tree_expr_nonzero_p@2)
+       @3)
+      (ne:c@4 @0 @1))
+    (bit_ior
+      (cmp
+       { build_zero_cst (TREE_TYPE (@0)); }
+       @3)
+      @4)))
+
+/* (a ^ b) cmp c || a != b --> (0 cmp c || a != b). */
+(for cmp (simple_comparison)
+  (simplify
+    (bit_ior
+      (cmp:c
+       (bit_xor:c @0 @1)
+       @2)
+      (ne:c@3 @0 @1))
+    (bit_ior
+      (cmp
+       { build_zero_cst (TREE_TYPE (@0)); }
+       @2)
+      @3)))
+
 /* We can't reassociate at all for saturating types.  */
 (if (!TYPE_SATURATING (type))
 

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-and-or.c b/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-and-or.c
new file mode 100644 (file)
index 0000000..e5dc98e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-and-or.c
@@ -0,0 +1,55 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+typedef unsigned long int uint64_t;
+
+int cmp1(int d1, int d2) {
+  if (((d1 ^ d2) & 0xabcd) == 0 || d1 != d2)
+    return 0;
+  return 1;
+}
+
+int cmp2(int d1, int d2) {
+  if (d1 != d2 || ((d1 ^ d2) & 0xabcd) == 0)
+    return 0;
+  return 1;
+}
+
+int cmp3(int d1, int d2) {
+  if (10 > (0xabcd & (d2 ^ d1)) || d2 != d1)
+    return 0;
+  return 1;
+}
+
+int cmp4(int d1, int d2) {
+  if (d2 != d1 || 10 > (0xabcd & (d2 ^ d1)))
+    return 0;
+  return 1;
+}
+
+int cmp1_64(uint64_t d1, uint64_t d2) {
+  if (((d1 ^ d2) & 0xabcd) == 0 || d1 != d2)
+    return 0;
+  return 1;
+}
+
+int cmp2_64(uint64_t d1, uint64_t d2) {
+  if (d1 != d2 || ((d1 ^ d2) & 0xabcd) == 0)
+    return 0;
+  return 1;
+}
+
+int cmp3_64(uint64_t d1, uint64_t d2) {
+  if (10 > (0xabcd & (d2 ^ d1)) || d2 != d1)
+    return 0;
+  return 1;
+}
+
+int cmp4_64(uint64_t d1, uint64_t d2) {
+  if (d2 != d1 || 10 > (0xabcd & (d2 ^ d1)))
+    return 0;
+  return 1;
+}
+
+/* The if should be removed, so the condition should not exist */
+/* { dg-final { scan-tree-dump-not "d1_\[0-9\]+.D. \\^ d2_\[0-9\]+.D." "optimized" } } */

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-or.c b/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-or.c
new file mode 100644 (file)
index 0000000..c55cfbc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fold-xor-or.c
@@ -0,0 +1,55 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+typedef unsigned long int uint64_t;
+
+int cmp1(int d1, int d2) {
+  if ((d1 ^ d2) == 0xabcd || d1 != d2)
+    return 0;
+  return 1;
+}
+
+int cmp2(int d1, int d2) {
+  if (d1 != d2 || (d1 ^ d2) == 0xabcd)
+    return 0;
+  return 1;
+}
+
+int cmp3(int d1, int d2) {
+  if (0xabcd > (d2 ^ d1) || d2 != d1)
+    return 0;
+  return 1;
+}
+
+int cmp4(int d1, int d2) {
+  if (d2 != d1 || 0xabcd > (d2 ^ d1))
+    return 0;
+  return 1;
+}
+
+int cmp1_64(uint64_t d1, uint64_t d2) {
+  if ((d1 ^ d2) == 0xabcd || d1 != d2)
+    return 0;
+  return 1;
+}
+
+int cmp2_64(uint64_t d1, uint64_t d2) {
+  if (d1 != d2 || (d1 ^ d2) == 0xabcd)
+    return 0;
+  return 1;
+}
+
+int cmp3_64(uint64_t d1, uint64_t d2) {
+  if (0xabcd > (d2 ^ d1) || d2 != d1)
+    return 0;
+  return 1;
+}
+
+int cmp4_64(uint64_t d1, uint64_t d2) {
+  if (d2 != d1 || 0xabcd > (d2 ^ d1))
+    return 0;
+  return 1;
+}
+
+/* The if should be removed, so the condition should not exist */
+/* { dg-final { scan-tree-dump-not "d1_\[0-9\]+.D. \\^ d2_\[0-9\]+.D." "optimized" } } */