Yes, the MinGW toolchain can handle this by specifying the alignment of a common symbol using the aligncomm directive. The MSVC toolchain has no such mechanism.
This is why the check uses isKnownWindowsMSVCEnvironment. On Tue, Jan 8, 2019 at 1:09 PM Shoaib Meenai <smee...@fb.com> wrote: > It checks for both OS=Win32 and Environment=MSVC, so that wouldn't cover > other COFF environments. wbs (Martin Storsjo) mentioned on IRC that MinGW > adds an aligncomm directive to specify alignment for common symbols, so > perhaps that's part of it? > > > > *From: *"Keane, Erich" <erich.ke...@intel.com> > *Date: *Tuesday, January 8, 2019 at 1:04 PM > *To: *Shoaib Meenai <smee...@fb.com>, "cfe-commits@lists.llvm.org" < > cfe-commits@lists.llvm.org>, David Majnemer <david.majne...@gmail.com> > *Subject: *RE: r350643 - Limit COFF 'common' emission to <=32 alignment > types. > > > > Yep, exactly. I looked, and isKnownWindowsMSVCEnvironment checks for > OS=Win32, which I believe would be different for other architectures. > > > > *From:* Shoaib Meenai [mailto:smee...@fb.com] > *Sent:* Tuesday, January 8, 2019 12:41 PM > *To:* Keane, Erich <erich.ke...@intel.com>; cfe-commits@lists.llvm.org; > David Majnemer <david.majne...@gmail.com> > *Subject:* Re: r350643 - Limit COFF 'common' emission to <=32 alignment > types. > > > > Ah, looks like you were originally checking for COFF, and then David > suggested checking for MSVC instead? I'm curious about why, although I'm > sure the suggestion is legit :) > > > > *From: *cfe-commits <cfe-commits-boun...@lists.llvm.org> on behalf of > Shoaib Meenai via cfe-commits <cfe-commits@lists.llvm.org> > *Reply-To: *Shoaib Meenai <smee...@fb.com> > *Date: *Tuesday, January 8, 2019 at 12:39 PM > *To: *Erich Keane <erich.ke...@intel.com>, "cfe-commits@lists.llvm.org" < > cfe-commits@lists.llvm.org> > *Subject: *Re: r350643 - Limit COFF 'common' emission to <=32 alignment > types. > > > > Why does this check for isKnownWindowsMSVCEnvironment specifically? > Wouldn't any COFF target (windows-cygnus, windows-gnu, windows-itanium, > etc.) have the same limitation, since it's an object file format issue and > not an ABI issue? > > > > *From: *cfe-commits <cfe-commits-boun...@lists.llvm.org> on behalf of > Erich Keane via cfe-commits <cfe-commits@lists.llvm.org> > *Reply-To: *Erich Keane <erich.ke...@intel.com> > *Date: *Tuesday, January 8, 2019 at 10:48 AM > *To: *"cfe-commits@lists.llvm.org" <cfe-commits@lists.llvm.org> > *Subject: *r350643 - Limit COFF 'common' emission to <=32 alignment types. > > > > Author: erichkeane > > Date: Tue Jan 8 10:44:22 2019 > > New Revision: 350643 > > > > URL: > https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D350643-26view-3Drev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=Ph9GOtRaQERmqyeJeAJTFwV3sg3q8fE05FlJ3qwNx4I&e= > > Log: > > Limit COFF 'common' emission to <=32 alignment types. > > > > As reported in PR33035, LLVM crashes if given a common object with an > > alignment of greater than 32 bits. This is because the COFF file format > > does not support these alignments, so emitting them is broken anyway. > > > > This patch changes any global definitions greater than 32 bit alignment > > to no longer be in 'common'. > > > > > https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_show-5Fbug.cgi-3Fid-3D33035&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=ac1NEHuvztd6jSTCsOUJajkklfeyqdzW-xqtddJ-hvM&e= > > > > Differential Revision: > https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D56391&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=AucP9Sp-DYHSaOP-sPfpAOrww3xwdh8FjQkHrLZhhyo&e= > > > > Change-Id: I48609289753b7f3b58c5e2bc1712756750fbd45a > > > > Added: > > cfe/trunk/test/CodeGen/microsoft-no-common-align.c > > Modified: > > cfe/trunk/lib/CodeGen/CodeGenModule.cpp > > > > Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp > > URL: > https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_cfe_trunk_lib_CodeGen_CodeGenModule.cpp-3Frev-3D350643-26r1-3D350642-26r2-3D350643-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=gmTnEmW03ruG8LbJluf5Z4yQcxM64QP7Ce1VTnVqvPo&e= > > > ============================================================================== > > --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original) > > +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Tue Jan 8 10:44:22 2019 > > @@ -3761,6 +3761,11 @@ static bool isVarDeclStrongDefinition(co > > } > > } > > } > > + // COFF doesn't support alignments greater than 32, so these cannot be > > + // in common. > > + if (Context.getTargetInfo().getTriple().isKnownWindowsMSVCEnvironment() > && > > + Context.getTypeAlignIfKnown(D->getType()) > 32) > > + return true; > > return false; > > } > > > > Added: cfe/trunk/test/CodeGen/microsoft-no-common-align.c > > URL: > https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_cfe_trunk_test_CodeGen_microsoft-2Dno-2Dcommon-2Dalign.c-3Frev-3D350643-26view-3Dauto&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=hzPmmVFbvg4OTEVpnQ5pIfy295Ne0-xAsctZs00WZgY&e= > > > ============================================================================== > > --- cfe/trunk/test/CodeGen/microsoft-no-common-align.c (added) > > +++ cfe/trunk/test/CodeGen/microsoft-no-common-align.c Tue Jan 8 10:44:22 > 2019 > > @@ -0,0 +1,8 @@ > > +// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -o - %s | > FileCheck %s > > +typedef float TooLargeAlignment __attribute__((__vector_size__(64))); > > +typedef float NormalAlignment __attribute__((__vector_size__(4))); > > + > > +TooLargeAlignment TooBig; > > +// CHECK: @TooBig = dso_local global <16 x float> zeroinitializer, align > 64 > > +NormalAlignment JustRight; > > +// CHECK: @JustRight = common dso_local global <1 x > float> zeroinitializer, align 4 > > > > > > _______________________________________________ > > cfe-commits mailing list > > cfe-commits@lists.llvm.org > > > https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.llvm.org_cgi-2Dbin_mailman_listinfo_cfe-2Dcommits&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=RNVKy_b0_Wgp_PTFDpvQXETsZdWubmT5SGnGz3GigS0&s=Myn7SZhcOe32EZiKZr4ByJAZOoFl5aIfmWV9555Vh9A&e= > > >
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