{"id":2224935,"url":"http://patchwork.ozlabs.org/api/patches/2224935/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/008301dcd02b$1253b880$36fb2980$@nextmovesoftware.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":"<008301dcd02b$1253b880$36fb2980$@nextmovesoftware.com>","list_archive_url":null,"date":"2026-04-19T18:33:50","name":"PR tree-optimization/124715: pow(0, -1) sets errno with -fmath-errno","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"c1a68d0f7762637a88cd5a24d2f7904973c26efc","submitter":{"id":68376,"url":"http://patchwork.ozlabs.org/api/people/68376/?format=json","name":"Roger Sayle","email":"roger@nextmovesoftware.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/008301dcd02b$1253b880$36fb2980$@nextmovesoftware.com/mbox/","series":[{"id":500523,"url":"http://patchwork.ozlabs.org/api/series/500523/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500523","date":"2026-04-19T18:33:50","name":"PR tree-optimization/124715: pow(0, -1) sets errno with -fmath-errno","version":1,"mbox":"http://patchwork.ozlabs.org/series/500523/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2224935/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2224935/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=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=nextmovesoftware.com header.i=@nextmovesoftware.com\n header.a=rsa-sha256 header.s=default header.b=OIShXfij;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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Ok for mainline or stage 1?\n\n\n2026-04-19 Roger Sayle \n\ngcc/ChangeLog\n PR tree-optimization/124715\n * match.pd (simpify pows): Check flag_errno_math before simplifying\n pow(x,-1) -> 1/x when x could be zero.\n\ngcc/testsuite/ChangeLog\n PR tree-optimization/124715\n * gcc.dg/no-math-errno-5.c: New test case.\n * gcc.dg/no-math-errno-6.c: Likewise.\n\nRoger\n--","diff":"diff --git a/gcc/match.pd b/gcc/match.pd\nindex 7b652afb43d..9fa0f7d2191 100644\n--- a/gcc/match.pd\n+++ b/gcc/match.pd\n@@ -9642,7 +9642,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)\n (if (real_equal (value, &dconst1))\n @0)\n /* pow(x,-1) -> 1/x. */\n- (if (real_equal (value, &dconstm1))\n+ (if (real_equal (value, &dconstm1)\n+\t && (!flag_errno_math || !real_maybe_zerop (@0)))\n (rdiv { build_real (type, dconst1); } @0))\n /* pow(x,0.5) -> sqrt(x). */\n (if (flag_unsafe_math_optimizations\ndiff --git a/gcc/testsuite/gcc.dg/no-math-errno-5.c b/gcc/testsuite/gcc.dg/no-math-errno-5.c\nnew file mode 100644\nindex 00000000000..9a64a9a7227\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/no-math-errno-5.c\n@@ -0,0 +1,14 @@\n+/* PR tree-optimization/124715 */\n+/* { dg-do compile } */\n+/* { dg-options \"-O2 -fno-math-errno -fdump-tree-optimized\" } */\n+/* { dg-require-effective-target c99_runtime } */\n+\n+extern double pow(double, double);\n+\n+double foo(double x)\n+{\n+ return pow(x,-1.0);\n+}\n+\n+/* { dg-final { scan-tree-dump-not \"pow \" \"optimized\" } } */\n+/* { dg-final { scan-tree-dump \" / \" \"optimized\" } } */\ndiff --git a/gcc/testsuite/gcc.dg/no-math-errno-6.c b/gcc/testsuite/gcc.dg/no-math-errno-6.c\nnew file mode 100644\nindex 00000000000..2b3ce04c51d\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/no-math-errno-6.c\n@@ -0,0 +1,14 @@\n+/* PR tree-optimization/124715 */\n+/* { dg-do compile } */\n+/* { dg-options \"-O2 -fmath-errno -fdump-tree-optimized\" } */\n+/* { dg-require-effective-target c99_runtime } */\n+\n+extern double pow(double, double);\n+\n+double foo(double x)\n+{\n+ return pow(x,-1.0);\n+}\n+\n+/* { dg-final { scan-tree-dump-not \" / \" \"optimized\" } } */\n+/* { dg-final { scan-tree-dump \"pow \" \"optimized\" } } */\n","prefixes":[]}