Re: [PATCH v3] simplify-rtx.cc:Simplify XOR(AND(ROTATE(~1) A) ASHIFT(1 A)) to IOR.

[Jiawei]

Committed to trunk, thanks.

Jiawei

在 2025/6/13 21:02, Richard Sandiford 写道:

Jiawei <jia...@iscas.ac.cn> writes:

This patch adds a new simplification rule to `simplify-rtx.cc` that
handles a common bit manipulation pattern involving a single-bit set
and clear followed by XOR.

The transformation targets RTL of the form:

   (xor (and (rotate (~1) A) B) (ashift 1 A))

which is semantically equivalent to:

   B | (1 << A)

- v3 log:
   Update RTL format, remove commas.
   Only apply on SHIFT_COUNT_TRUNCATED target.
   check '!side_effects_p' on XEXP (op1, 1).

gcc/ChangeLog:

        * simplify-rtx.cc (simplify_context::simplify_binary_operation_1): 
Handle
more logical simplifications.

---
  gcc/simplify-rtx.cc | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

OK, thanks.

Richard

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index b34fd2f4b9e..cbe61b49bf6 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -4063,6 +4063,20 @@ simplify_context::simplify_binary_operation_1 (rtx_code 
code,
          && rtx_equal_p (XEXP (XEXP (op0, 0), 0), op1))
        return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1);

+ /* Convert (xor (and (rotate (~1) A) B) (ashift 1 A))

+        into B | (1 << A).  */
+      if (SHIFT_COUNT_TRUNCATED
+         && GET_CODE (op0) == AND
+         && GET_CODE (XEXP (op0, 0)) == ROTATE
+         && CONST_INT_P (XEXP (XEXP (op0, 0), 0))
+         && INTVAL (XEXP (XEXP (op0, 0), 0)) == -2
+         && GET_CODE (op1) == ASHIFT
+         && CONST_INT_P (XEXP (op1, 0))
+         && INTVAL (XEXP (op1, 0)) == 1
+         && rtx_equal_p (XEXP (XEXP (op0, 0), 1), XEXP (op1, 1))
+         && !side_effects_p (XEXP (op1, 1)))
+       return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1);
+
        tem = simplify_with_subreg_not (code, mode, op0, op1);
        if (tem)
        return tem;