[gcc r17-2824] MATCH: Simplify zero/sign extension bit operations [PR122848]

https://gcc.gnu.org/g:ece564fdaa15a0da008cedd881afcd3f0f4dbd5a

commit r17-2824-gece564fdaa15a0da008cedd881afcd3f0f4dbd5a
Author: Eikansh Gupta <[email protected]>
Date:   Wed Jun 3 15:46:29 2026 +0530

    MATCH: Simplify zero/sign extension bit operations [PR122848]
    
    Fold bitwise operations involving zero and sign extensions from the same
    low-precision value.  The AND case folds to the zero extension, and the
    OR case folds to the sign extension.
    
            PR tree-optimization/122848
    
    gcc/ChangeLog:
    
            * match.pd (zero_extend & sign_extend -> zero_extend): New pattern.
            (zero_extend | sign_extend -> sign_extend): Likewise.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/tree-ssa/pr122848.c: New test.
    
    Signed-off-by: Eikansh Gupta <[email protected]>

Diff:
---
 gcc/match.pd                             | 15 +++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr122848.c | 70 ++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/gcc/match.pd b/gcc/match.pd
index 6c9bb0da7cf0..ce02ebf26997 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1488,6 +1488,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        && bitwise_inverted_equal_p (@0, @1, wascmp))
    { wascmp ? constant_boolean_node (false, type) : build_zero_cst (type); })))
 
+/* zero_extend (X) & sign_extend (X) -> zero_extend (X) and
+   zero_extend (X) | sign_extend (X) -> sign_extend (X)  */
+(for bitop (bit_and bit_ior)
+ (simplify
+  (bitop:c (convert @0) (convert (nop_convert@1 @0)))
+  (if (INTEGRAL_TYPE_P (type)
+       && INTEGRAL_TYPE_P (TREE_TYPE (@0))
+       && INTEGRAL_TYPE_P (TREE_TYPE (@1))
+       && TYPE_UNSIGNED (TREE_TYPE (@0)) != TYPE_UNSIGNED (TREE_TYPE (@1))
+       && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (TREE_TYPE (@1))
+       && TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (type))
+   (if ((bitop == BIT_AND_EXPR) == TYPE_UNSIGNED (TREE_TYPE (@0)))
+    (convert @0)
+    (convert @1)))))
+
 /* PR71636: Transform x & ((1U << b) - 1) -> x & ~(~0U << b);  */
 (simplify
   (bit_and:c @0 (plus:s (lshift:s integer_onep @1) integer_minus_onep))
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr122848.c b/gcc/testsuite/gcc.dg/tree-ssa/pr122848.c
new file mode 100644
index 000000000000..363e000f43e1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr122848.c
@@ -0,0 +1,70 @@
+/* PR tree-optimization/122848 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int f1 (unsigned char a)
+{
+  int t = a;
+  int t1 = (signed char) a;
+  return t & t1;
+}
+
+int f2 (unsigned char a)
+{
+  int t = a;
+  int t1 = (signed char) a;
+  return t1 & t;
+}
+
+int f3 (unsigned char a)
+{
+  return (int) a & (int) (signed char) a;
+}
+
+int f4 (unsigned short a)
+{
+  return (int) a & (int) (short) a;
+}
+
+long f5 (unsigned int a)
+{
+  return (long) a & (long) (int) a;
+}
+
+unsigned int f6 (unsigned char a)
+{
+  return (unsigned int) a & (unsigned int) (signed char) a;
+}
+
+int f7 (unsigned char a)
+{
+  return (int) a | (int) (signed char) a;
+}
+
+int f8 (unsigned short a)
+{
+  return (int) a | (int) (short) a;
+}
+
+int f9 (signed char a)
+{
+  return (int) (unsigned char) a & (int) a;
+}
+
+int f10 (signed char a)
+{
+  return (int) a & (int) (unsigned char) a;
+}
+
+int f11 (signed char a)
+{
+  return (int) (unsigned char) a | (int) a;
+}
+
+int f12 (signed short a)
+{
+  return (int) (unsigned short) a | (int) a;
+}
+
+/* { dg-final { scan-tree-dump-not " & " "optimized" } } */
+/* { dg-final { scan-tree-dump-not " \\| " "optimized" } } */