{"id":2175301,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2175301/?format=json","project":{"id":41,"url":"http://patchwork.ozlabs.org/api/1.0/projects/41/?format=json","name":"GNU C Library","link_name":"glibc","list_id":"libc-alpha.sourceware.org","list_email":"libc-alpha@sourceware.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20251217175554.1157780-6-adhemerval.zanella@linaro.org>","date":"2025-12-17T17:51:51","name":"[5/8] math: Fix potential underflow on ldbl-128 erfl","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"dca749a4785b26ee87e1c12e6bb25c56a4c2a1bb","submitter":{"id":66065,"url":"http://patchwork.ozlabs.org/api/1.0/people/66065/?format=json","name":"Adhemerval Zanella Netto","email":"adhemerval.zanella@linaro.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/glibc/patch/20251217175554.1157780-6-adhemerval.zanella@linaro.org/mbox/","series":[{"id":485739,"url":"http://patchwork.ozlabs.org/api/1.0/series/485739/?format=json","date":"2025-12-17T17:51:48","name":"Improve test when building with clang","version":1,"mbox":"http://patchwork.ozlabs.org/series/485739/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2175301/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=DDT6Y2oZ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=38.145.34.32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (2048-bit key,\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=DDT6Y2oZ","sourceware.org;\n dmarc=pass (p=none dis=none) header.from=linaro.org","sourceware.org; spf=pass smtp.mailfrom=linaro.org","server2.sourceware.org;\n arc=none smtp.remote-ip=209.85.210.170"],"Received":["from vm01.sourceware.org (vm01.sourceware.org [38.145.34.32])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4dWhQL0qBCz1y0P\n\tfor ; Thu, 18 Dec 2025 04:59:38 +1100 (AEDT)","from vm01.sourceware.org (localhost [127.0.0.1])\n\tby sourceware.org (Postfix) with ESMTP id 2E10B4BA2E25\n\tfor ; Wed, 17 Dec 2025 17:59:36 +0000 (GMT)","from mail-pf1-f170.google.com (mail-pf1-f170.google.com\n [209.85.210.170])\n by sourceware.org (Postfix) with ESMTPS id C70894BA2E06\n for ; Wed, 17 Dec 2025 17:56:10 +0000 (GMT)","by mail-pf1-f170.google.com with SMTP id\n d2e1a72fcca58-7bab7c997eeso6792796b3a.0\n for ; Wed, 17 Dec 2025 09:56:10 -0800 (PST)","from ubuntu-vm.. 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J . Lu\" , Collin Funk ,\n Sam James ","Subject":"[PATCH 5/8] math: Fix potential underflow on ldbl-128 erfl","Date":"Wed, 17 Dec 2025 14:51:51 -0300","Message-ID":"<20251217175554.1157780-6-adhemerval.zanella@linaro.org>","X-Mailer":"git-send-email 2.43.0","In-Reply-To":"<20251217175554.1157780-1-adhemerval.zanella@linaro.org>","References":"<20251217175554.1157780-1-adhemerval.zanella@linaro.org>","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-BeenThere":"libc-alpha@sourceware.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Libc-alpha mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org"},"content":"The multiplication operation is required only if the branch is taken,\nand the compiler might not optimize it away.\n\nIt fixes the following issues when the testcase is built with clang:\n\nFAIL: math/test-ldouble-erf\nFailure: erf (-0x4p-16384): Exception \"Underflow\" set\nFailure: erf (0x1p-10000): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded54f38760a41abb84p-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded54f38760a41abb88p-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded54f4p-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded54f8p-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded5518p-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded551cp-16384): Exception \"Underflow\" set\nFailure: erf (0x3.8b7f12369ded552p-16384): Exception \"Underflow\" set\nFailure: erf (0x4p-16384): Exception \"Underflow\" set\nFailure: erf_downward (-0x4p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x1p-10000): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded54f38760a41abb84p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded54f38760a41abb88p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded54f4p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded54f8p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded5518p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded551cp-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x3.8b7f12369ded552p-16384): Exception \"Underflow\" set\nFailure: erf_downward (0x4p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (-0x4p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x1p-10000): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded54f38760a41abb84p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded54f38760a41abb88p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded54f4p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded54f8p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded5518p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded551cp-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x3.8b7f12369ded552p-16384): Exception \"Underflow\" set\nFailure: erf_towardzero (0x4p-16384): Exception \"Underflow\" set\nFailure: erf_upward (-0x4p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x1p-10000): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded54f38760a41abb84p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded54f38760a41abb88p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded54f4p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded54f8p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded5518p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded551cp-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x3.8b7f12369ded552p-16384): Exception \"Underflow\" set\nFailure: erf_upward (0x4p-16384): Exception \"Underflow\" set\n\nChecked on x86_64-linux-gnu and aarch64-linux-gnu with gcc-15 and\nclang-18.\n---\n sysdeps/ieee754/ldbl-128/s_erfl.c | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)","diff":"diff --git a/sysdeps/ieee754/ldbl-128/s_erfl.c b/sysdeps/ieee754/ldbl-128/s_erfl.c\nindex 1cbedc249d..e52d88bde3 100644\n--- a/sysdeps/ieee754/ldbl-128/s_erfl.c\n+++ b/sysdeps/ieee754/ldbl-128/s_erfl.c\n@@ -778,7 +778,6 @@ __erfl (_Float128 x)\n }\n u.parts32.w0 = ix;\n a = u.value;\n- z = x * x;\n if (ix < 0x3ffec000) /* a < 0.875 */\n {\n if (ix < 0x3fc60000) /* |x|<2**-57 */\n@@ -792,6 +791,7 @@ __erfl (_Float128 x)\n \t }\n \t return x + efx * x;\n \t}\n+ z = x * x;\n y = a + a * neval (z, TN1, NTN1) / deval (z, TD1, NTD1);\n }\n else\n","prefixes":["5/8"]}