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Thu, 22 Feb 2024 12:59:27 -0800 (PST) Received: from gkm.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id rs11-20020a17090b2b8b00b0029a4db713b9sm1932801pjb.39.2024.02.22.12.59.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Feb 2024 12:59:27 -0800 (PST) From: Greg McGary To: gcc-patches@gcc.gnu.org Cc: Greg McGary Subject: [PATCH] combine: Don't simplify high part of paradoxical-SUBREG-of-MEM on machines that sign-extend loads [PR113010] Date: Thu, 22 Feb 2024 12:59:18 -0800 Message-Id: <20240222205918.3871954-1-gkm@rivosinc.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Spam-Status: No, score=-11.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org The sign bit of a sign-extending load cannot be known until runtime, so don't attempt to simplify it in the combiner. 2024-02-22 Greg McGary PR rtl-optimization/113010 * combine.cc (simplify_comparison): Don't simplify high part of paradoxical-SUBREG-of-MEM on machines that sign-extend loads * gcc.c-torture/execute/pr113010.c: New test. --- gcc/combine.cc | 10 ++++++++-- gcc/testsuite/gcc.c-torture/execute/pr113010.c | 9 +++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr113010.c diff --git a/gcc/combine.cc b/gcc/combine.cc index 812553c091e..736206242e1 100644 --- a/gcc/combine.cc +++ b/gcc/combine.cc @@ -12550,9 +12550,15 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1) } /* If the inner mode is narrower and we are extracting the low part, - we can treat the SUBREG as if it were a ZERO_EXTEND. */ + we can treat the SUBREG as if it were a ZERO_EXTEND ... */ if (paradoxical_subreg_p (op0)) - ; + { + /* ... except we can't treat as ZERO_EXTEND when a machine + automatically sign-extends loads. */ + if (MEM_P (SUBREG_REG (op0)) && WORD_REGISTER_OPERATIONS + && load_extend_op (inner_mode) == SIGN_EXTEND) + break; + } else if (subreg_lowpart_p (op0) && GET_MODE_CLASS (mode) == MODE_INT && is_int_mode (GET_MODE (SUBREG_REG (op0)), &inner_mode) diff --git a/gcc/testsuite/gcc.c-torture/execute/pr113010.c b/gcc/testsuite/gcc.c-torture/execute/pr113010.c new file mode 100644 index 00000000000..a95c613c1df --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr113010.c @@ -0,0 +1,9 @@ +int minus_1 = -1; + +int +main () +{ + if ((0, 0xfffffffful) >= minus_1) + __builtin_abort (); + return 0; +}