From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luc Van Oostenryck Subject: [PATCH 3/3] simplify '(x || x)' and '(x && x)' Date: Sun, 11 Dec 2016 22:13:28 +0100 Message-ID: <20161211211328.26735-4-luc.vanoostenryck@gmail.com> References: <20161211211328.26735-1-luc.vanoostenryck@gmail.com> Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:34935 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753844AbcLKVQE (ORCPT ); Sun, 11 Dec 2016 16:16:04 -0500 Received: by mail-wm0-f66.google.com with SMTP id a20so7108372wme.2 for ; Sun, 11 Dec 2016 13:16:03 -0800 (PST) In-Reply-To: <20161211211328.26735-1-luc.vanoostenryck@gmail.com> Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: linux-sparse@vger.kernel.org Cc: Christopher Li , Luc Van Oostenryck The operators '||' and '&&' being idempotent, the expressions '(x || x)' and '(x && x)' can be simplified to a test against zero. Note: they could even be replaced by 'x' itself but only if 'x' is already a boolean expression/has already been tested against zero. If it is the case, the redundant test this will be optimized away in further steps. For example, test-linearize on the following code: int ior(int a) { return a || a; } emitted the following instructions: or-bool.32 %r3 <- %arg1, %arg1 after the patch, it now emits: setne.32 %r3 <- %arg1, $0 which is easier to combine with others simplifications. Signed-off-by: Luc Van Oostenryck --- simplify.c | 8 ++++---- validation/optim/bool-same-args.c | 12 ++++++++++++ 2 files changed, 16 insertions(+), 4 deletions(-) create mode 100644 validation/optim/bool-same-args.c diff --git a/simplify.c b/simplify.c index d076ebb5..169561fd 100644 --- a/simplify.c +++ b/simplify.c @@ -578,10 +578,10 @@ static int simplify_binop_same_args(struct instruction *insn, pseudo_t arg) case OP_AND_BOOL: case OP_OR_BOOL: - // simplification is correct only if the operands - // have already been compared against zero which - // is not enforced. - break; + remove_usage(arg, &insn->src2); + insn->src2 = value_pseudo(0); + insn->opcode = OP_SET_NE; + return REPEAT_CSE; default: break; diff --git a/validation/optim/bool-same-args.c b/validation/optim/bool-same-args.c new file mode 100644 index 00000000..0ae4684e --- /dev/null +++ b/validation/optim/bool-same-args.c @@ -0,0 +1,12 @@ +static int ior(int a) { return a || a; } +static int and(int a) { return a && a; } + +/* + * check-name: bool-same-args + * check-command: test-linearize $file + * check-output-ignore + * + * check-output-excludes: or-bool\\. + * check-output-excludes: and-bool\\. + * check-output-contains: setne\\. + */ -- 2.10.2