From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 8 Apr 2025 13:14:58 +0000 (+0200)
Subject: simplify-rtx: Fix up POPCOUNT optimization [PR119672]
X-Git-Tag: basepoints/gcc-16~237
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=04918a2d3f20b02ac3efad1096c33894d57789a0;p=thirdparty%2Fgcc.git

simplify-rtx: Fix up POPCOUNT optimization [PR119672]

The gcc.dg/vect/pr113281-1.c test and many others ICE on riscv since
presumably the r15-9238 change which allowed more cases of vector modes
in simplify_const_relational_operation.
In the testcase it is EQ of
(popcount:SI (unspec:RVVMF32BI [
            (and:RVVMF32BI (const_vector:RVVMF32BI repeat [
                        (const_int 1 [0x1])
                    ])
                (reg:RVVMF32BI 147 [ mask__6.8_35 ]))
            (reg:SI 143 [ _41 ])
            (const_int 0 [0])
            (reg:SI 66 vl)
            (reg:SI 67 vtype)
        ] UNSPEC_VPREDICATE))
and
(const_int 0 [0])
which it tries to fold as EQ comparison of
(unspec:RVVMF32BI [
        (and:RVVMF32BI (const_vector:RVVMF32BI repeat [
                    (const_int 1 [0x1])
                ])
            (reg:RVVMF32BI 147 [ mask__6.8_35 ]))
        (reg:SI 143 [ _41 ])
        (const_int 0 [0])
        (reg:SI 66 vl)
        (reg:SI 67 vtype)
    ] UNSPEC_VPREDICATE)
with
(const_int 0 [0])
which ICEs because const0_rtx isn't a vector.
Fixed by using CONST0_RTX, so that we pass
(const_vector:RVVMF32BI repeat [
        (const_int 0 [0])
    ])
instead.

2025-04-08  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/119672
	* simplify-rtx.cc (simplify_context::simplify_relational_operation_1):
	For POPCOUNT == 0 or != 0 optimizations use
	CONST0_RTX (GET_MODE (XEXP (op0, 0))) rather than const0_rtx.
---

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 6f969effdf9..88d31a71c05 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -6465,14 +6465,16 @@ simplify_context::simplify_relational_operation_1 (rtx_code code,
       case LEU:
 	/* (eq (popcount x) (const_int 0)) -> (eq x (const_int 0)).  */
 	return simplify_gen_relational (EQ, mode, GET_MODE (XEXP (op0, 0)),
-					XEXP (op0, 0), const0_rtx);
+					XEXP (op0, 0),
+					CONST0_RTX (GET_MODE (XEXP (op0, 0))));
 
       case NE:
       case GT:
       case GTU:
 	/* (ne (popcount x) (const_int 0)) -> (ne x (const_int 0)).  */
 	return simplify_gen_relational (NE, mode, GET_MODE (XEXP (op0, 0)),
-					XEXP (op0, 0), const0_rtx);
+					XEXP (op0, 0),
+					CONST0_RTX (GET_MODE (XEXP (op0, 0))));
 
       default:
 	break;