From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1251) id 6DF0038582A3; Sat, 18 Jun 2022 08:10:25 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 6DF0038582A3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Roger Sayle To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-1162] PR tree-optimization/105835: Two narrowing patterns for match.pd. X-Act-Checkin: gcc X-Git-Author: Roger Sayle X-Git-Refname: refs/heads/master X-Git-Oldrev: 479b6f449ee999501ad6eff0b7db8d0cd5b2d28d X-Git-Newrev: 9991d84d2a84355fd3fc9afc89a963f45991bfa9 Message-Id: <20220618081025.6DF0038582A3@sourceware.org> Date: Sat, 18 Jun 2022 08:10:25 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Jun 2022 08:10:25 -0000 https://gcc.gnu.org/g:9991d84d2a84355fd3fc9afc89a963f45991bfa9 commit r13-1162-g9991d84d2a84355fd3fc9afc89a963f45991bfa9 Author: Roger Sayle Date: Sat Jun 18 09:06:20 2022 +0100 PR tree-optimization/105835: Two narrowing patterns for match.pd. This patch resolves PR tree-optimization/105835, which is a code quality (dead code elimination) regression at -O1 triggered/exposed by a recent change to canonicalize X&-Y as X*Y. The new (shorter) form exposes some missed optimization opportunities that can be handled by adding some extra simplifications to match.pd. One transformation is to simplify "(short)(x ? 65535 : 0)" into the equivalent "x ? -1 : 0", or more accurately x ? (short)-1 : (short)0", as INTEGER_CSTs record their type, and integer conversions can be pushed inside COND_EXPRs reducing the number of gimple statements. The other transformation is that (short)(X * 65535), where X is [0,1], into the equivalent (short)X * -1, (or again (short)-1 where tree's INTEGER_CSTs encode their type). This is valid because multiplications where one operand is [0,1] are guaranteed not to overflow, and hence integer conversions can also be pushed inside these multiplications. These narrowing conversion optimizations can be identified by range analyses, such as EVRP, but these are only performed at -O2 and above, which is why this regression is only visible with -O1. 2022-06-18 Roger Sayle gcc/ChangeLog PR tree-optimization/105835 * match.pd (convert (mult zero_one_valued_p@1 INTEGER_CST@2)): Narrow integer multiplication by a zero_one_valued_p operand. (convert (cond @1 INTEGER_CST@2 INTEGER_CST@3)): Push integer conversions inside COND_EXPR where both data operands are integer constants. gcc/testsuite/ChangeLog PR tree-optimization/105835 * gcc.dg/pr105835.c: New test case. Diff: --- gcc/match.pd | 15 +++++++++++++++ gcc/testsuite/gcc.dg/pr105835.c | 18 ++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/gcc/match.pd b/gcc/match.pd index 3e9572e4c9c..a63b649841b 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1881,6 +1881,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) && !TYPE_UNSIGNED (TREE_TYPE (@0))) (mult (convert @0) @1))) +/* Narrow integer multiplication by a zero_one_valued_p operand. + Multiplication by [0,1] is guaranteed not to overflow. */ +(simplify + (convert (mult@0 zero_one_valued_p@1 INTEGER_CST@2)) + (if (INTEGRAL_TYPE_P (type) + && INTEGRAL_TYPE_P (TREE_TYPE (@0)) + && TYPE_PRECISION (type) <= TYPE_PRECISION (TREE_TYPE (@0))) + (mult (convert @1) (convert @2)))) + /* Convert ~ (-A) to A - 1. */ (simplify (bit_not (convert? (negate @0))) @@ -4356,6 +4365,12 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) ) #endif +(simplify + (convert (cond@0 @1 INTEGER_CST@2 INTEGER_CST@3)) + (if (INTEGRAL_TYPE_P (type) + && INTEGRAL_TYPE_P (TREE_TYPE (@0))) + (cond @1 (convert @2) (convert @3)))) + /* Simplification moved from fold_cond_expr_with_comparison. It may also be extended. */ /* This pattern implements two kinds simplification: diff --git a/gcc/testsuite/gcc.dg/pr105835.c b/gcc/testsuite/gcc.dg/pr105835.c new file mode 100644 index 00000000000..354c81c6720 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr105835.c @@ -0,0 +1,18 @@ +/* { dg-do compile } */ +/* { dg-options "-O1 -fdump-tree-optimized" } */ + +void foo(); + +static int b; + +static short a(short c, unsigned short d) { return c - d; } + +int main() { + int e = -(0 < b); + if (a(1, e)) + b = 0; + else + foo(); +} + +/* { dg-final { scan-tree-dump-not "goto" "optimized" } } */