From bd848fa1d8968ffbbc783c70bdecd8b365085e95 Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <oliva@adacore.com>
Date: Wed, 4 Feb 2026 23:48:55 -0300
Subject: [PATCH] simplify-rtx: fix riscv redundant-bitmap-2.C

The insn simplification expected by the test, to get a bset
instruction, has been prevented since r15-9239, because we get rotates
for bit clear and shifts for bit flip, and we don't know how to
simplify those.

Teach the rtl simplifier, at the spots where it had been extended to
handle these logical simplifications, to also handle these less
obvious negations.

for  gcc/ChangeLog

	* simplify-rtx.cc (negated_ops_p): New.
	(simplify_context::simplify_binary_operation_1): Use it.
---
 gcc/simplify-rtx.cc | 53 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 12 deletions(-)

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 72c6bbb7d67..88aa95c8123 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -3074,6 +3074,39 @@ simplify_with_subreg_not (rtx_code binop, machine_mode mode, rtx op0, rtx op1)
     return simplify_gen_binary (binop, mode, op0, new_not);
 }
 
+/* Return TRUE iff NOP is a negated form of OP, or vice-versa.  */
+static bool
+negated_ops_p (rtx nop, rtx op)
+{
+  /* Explicit negation.  */
+  if (GET_CODE (nop) == NOT
+      && rtx_equal_p (XEXP (nop, 0), op))
+    return true;
+  if (GET_CODE (op) == NOT
+      && rtx_equal_p (XEXP (op, 0), nop))
+    return true;
+
+  /* (~C <r A) is a negated form of (C << A) if C == 1.  */
+  if (GET_CODE (op) == ASHIFT
+      && GET_CODE (nop) == ROTATE
+      && XEXP (op, 0) == CONST1_RTX (GET_MODE (op))
+      && CONST_INT_P (XEXP (nop, 0))
+      && INTVAL (XEXP (nop, 0)) == -2
+      && rtx_equal_p (XEXP (op, 1), XEXP (nop, 1)))
+    return true;
+  if (GET_CODE (nop) == ASHIFT
+      && GET_CODE (op) == ROTATE
+      && XEXP (nop, 0) == CONST1_RTX (GET_MODE (op))
+      && CONST_INT_P (XEXP (nop, 0))
+      && INTVAL (XEXP (nop, 0)) == -2
+      && rtx_equal_p (XEXP (op, 1), XEXP (nop, 1)))
+    return true;
+
+  /* ??? Should we consider rotations of C and ~C by the same amount?  */
+
+  return false;
+}
+
 /* Subroutine of simplify_binary_operation.  Simplify a binary operation
    CODE with result mode MODE, operating on OP0 and OP1.  If OP0 and/or
    OP1 are constant pool references, TRUEOP0 and TRUEOP1 represent the
@@ -3861,8 +3894,7 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
 
       /* Convert (ior (and (not A) B) A) into A | B.  */
       if (GET_CODE (op0) == AND
-	  && GET_CODE (XEXP (op0, 0)) == NOT
-	  && rtx_equal_p (XEXP (XEXP (op0, 0), 0), op1))
+	  && negated_ops_p (XEXP (op0, 0), op1))
 	return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1);
 
       tem = simplify_with_subreg_not (code, mode, op0, op1);
@@ -4133,8 +4165,7 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
 
       /* Convert (xor (and (not A) B) A) into A | B.  */
       if (GET_CODE (op0) == AND
-	  && GET_CODE (XEXP (op0, 0)) == NOT
-	  && rtx_equal_p (XEXP (XEXP (op0, 0), 0), op1))
+	  && negated_ops_p (XEXP (op0, 0), op1))
 	return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1);
 
       /* Convert (xor (and (rotate (~1) A) B) (ashift 1 A))
@@ -4413,21 +4444,19 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
 	  && rtx_equal_p (op1, XEXP (XEXP (op0, 1), 0)))
 	return simplify_gen_binary (AND, mode, op1, XEXP (op0, 0));
 
-      /* (and (ior/xor (X Y) (not Y)) -> X & ~Y */
+      /* (and (ior/xor X Y) (not Y)) -> X & ~Y */
       if ((GET_CODE (op0) == IOR || GET_CODE (op0) == XOR)
-	  && GET_CODE (op1) == NOT
-	  && rtx_equal_p (XEXP (op1, 0), XEXP (op0, 1)))
+	  && negated_ops_p (op1, XEXP (op0, 1)))
 	return simplify_gen_binary (AND, mode, XEXP (op0, 0),
 				    simplify_gen_unary (NOT, mode,
-							XEXP (op1, 0),
+							XEXP (op0, 1),
 							mode));
-      /* (and (ior/xor (Y X) (not Y)) -> X & ~Y */
+      /* (and (ior/xor Y X) (not Y)) -> X & ~Y */
       if ((GET_CODE (op0) == IOR || GET_CODE (op0) == XOR)
-	  && GET_CODE (op1) == NOT
-	  && rtx_equal_p (XEXP (op1, 0), XEXP (op0, 0)))
+	  && negated_ops_p (op1, XEXP (op0, 0)))
 	return simplify_gen_binary (AND, mode, XEXP (op0, 1),
 				    simplify_gen_unary (NOT, mode,
-							XEXP (op1, 0),
+							XEXP (op0, 0),
 							mode));
 
       /* Convert (and (ior A C) (ior B C)) into (ior (and A B) C).  */
-- 
2.47.3