{"id":2232115,"url":"http://patchwork.ozlabs.org/api/patches/2232115/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260502180223.410876-1-avinal.xlvii@gmail.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260502180223.410876-1-avinal.xlvii@gmail.com>","list_archive_url":null,"date":"2026-05-02T18:02:23","name":"match: Optimize `A > B ? ABS(A) : B` to `MAX(A, B)` when B >= 0 [PR116700]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"7804b0269090dae9defad32420bffba27292bddf","submitter":{"id":88549,"url":"http://patchwork.ozlabs.org/api/people/88549/?format=json","name":"Avinal Kumar","email":"avinal.xlvii@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260502180223.410876-1-avinal.xlvii@gmail.com/mbox/","series":[{"id":502544,"url":"http://patchwork.ozlabs.org/api/series/502544/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=502544","date":"2026-05-02T18:02:23","name":"match: Optimize `A > B ? ABS(A) : B` to `MAX(A, B)` when B >= 0 [PR116700]","version":1,"mbox":"http://patchwork.ozlabs.org/series/502544/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2232115/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2232115/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=ffIihG+P;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (2048-bit key,\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=ffIihG+P","sourceware.org;\n dmarc=pass (p=none dis=none) header.from=gmail.com","sourceware.org; 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ABS(A) : B` to `MAX(A,\n B)` when B >= 0 [PR116700]","Date":"Sat, 2 May 2026 23:32:23 +0530","Message-ID":"<20260502180223.410876-1-avinal.xlvii@gmail.com>","X-Mailer":"git-send-email 2.54.0","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"When B is known to be non-negative and A > B, A must be positive,\nso ABS(A) == A. The whole expression (A > B ? ABS(A) : B) then\nsimplifies to MAX(A, B). This is caught at -O2 via VRP, but at\n-O1 phiopt1 produces ABS_EXPR and no later pass simplifies it.\n\n PR tree-optimization/116700\n\ngcc/ChangeLog:\n\n * match.pd: (A > B ? ABS(A) : B -> MAX(A, B)): New pattern\n for non-negative B.\n\ngcc/testsuite/ChangeLog:\n\n * gcc.dg/pr116700.c: New test.\n * gcc.dg/tree-ssa/phi-opt-48.c: New test.\n\nSigned-off-by: Avinal Kumar \n---\nI compared the changes in the suggested patch on bugzilla, understood patterns\nand tried to adapt them. The actual mechanism is still not completely understood\nto me. The tests are running fine but I think I am missing some cases.\n\nHere is how I ran the tests:\n\nmake -j$(nproc)\nmake check-gcc RUNTESTFLAGS=\"tree-ssa.exp=phi-opt-48.c\"\nmake check-gcc RUNTESTFLAGS=\"dg.exp=pr116700.c\"\n\nOn a side note, is there any trick/tips for building faster? I have a decent\nsystem (8C 16T and 64GB RAM) and it takes almost an hour.\n\n gcc/match.pd | 9 ++++++++\n gcc/testsuite/gcc.dg/pr116700.c | 13 +++++++++++\n gcc/testsuite/gcc.dg/tree-ssa/phi-opt-48.c | 25 ++++++++++++++++++++++\n 3 files changed, 47 insertions(+)\n create mode 100644 gcc/testsuite/gcc.dg/pr116700.c\n create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-48.c","diff":"diff --git a/gcc/match.pd b/gcc/match.pd\nindex dd9efb82c59..928f75c5a44 100644\n--- a/gcc/match.pd\n+++ b/gcc/match.pd\n@@ -7276,6 +7276,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)\n (if (INTEGRAL_TYPE_P (type))\n @3))\n \n+/* A > B ? ABS(A) : B -> MAX(A, B) when B is non-negative.\n+ When A > B >= 0, A is positive so ABS(A) = A = MAX(A, B).\n+ When A <= B, the result is B = MAX(A, B). */\n+(for cmp (gt ge)\n+ (simplify\n+ (cond (cmp:c @0 tree_expr_nonnegative_p@1) (abs @0) @1)\n+ (if (INTEGRAL_TYPE_P (type))\n+ (max @0 @1))))\n+\n /* (X + 1) > Y ? -X : 1 simplifies to X >= Y ? -X : 1 when\n X is unsigned, as when X + 1 overflows, X is -1, so -X == 1. */\n (simplify\ndiff --git a/gcc/testsuite/gcc.dg/pr116700.c b/gcc/testsuite/gcc.dg/pr116700.c\nnew file mode 100644\nindex 00000000000..a52388249a3\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/pr116700.c\n@@ -0,0 +1,13 @@\n+/* PR tree-optimization/116700 */\n+/* { dg-do compile } */\n+/* { dg-options \"-O1 -fdump-tree-phiopt1\" } */\n+\n+int f(unsigned char a, int b, int c)\n+{\n+ int t = a;\n+ if (c > t) t = (c > 0 ? c : -c);\n+ return t;\n+}\n+\n+/* { dg-final { scan-tree-dump \"MAX_EXPR\" \"phiopt1\" } } */\n+/* { dg-final { scan-tree-dump-not \"ABS_EXPR\" \"phiopt1\" } } */\ndiff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-48.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-48.c\nnew file mode 100644\nindex 00000000000..06317766457\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-48.c\n@@ -0,0 +1,25 @@\n+/* { dg-do compile } */\n+/* { dg-options \"-O1 -fdump-tree-phiopt1\" } */\n+\n+/* Test that (A > B) ? ABS(A) : B is simplified to MAX(A, B)\n+ when B is known to be non-negative. */\n+\n+int f(unsigned char a, int b, int c)\n+{\n+ int t = a;\n+ if (c > t)\n+ t = (c > 0 ? c : -c);\n+ return t;\n+}\n+\n+int f1(unsigned char a, int b, int c)\n+{\n+ int t = a;\n+ if (c > t) return (c > 0 ? c : -c);\n+ return t;\n+}\n+\n+/* Both functions should be converted to MAX_EXPR by phiopt1. */\n+/* { dg-final { scan-tree-dump-times \"MAX_EXPR\" 2 \"phiopt1\" } } */\n+/* { dg-final { scan-tree-dump-not \"ABS_EXPR\" \"phiopt1\" } } */\n+/* { dg-final { scan-tree-dump-not \"if \" \"phiopt1\" } } */\n","prefixes":[]}