Index: lib/CodeGen/CodeGenModule.cpp =================================================================== --- lib/CodeGen/CodeGenModule.cpp +++ lib/CodeGen/CodeGenModule.cpp @@ -3761,6 +3761,11 @@ } } } + // COFF doesn't support alignments greater than 32, so these cannot be + // in common. + if (Context.getTargetInfo().getTriple().isOSBinFormatCOFF() && + Context.getTypeAlignIfKnown(D->getType()) > 32) + return true; return false; } Index: test/CodeGen/microsoft-no-common-align.c =================================================================== --- /dev/null +++ test/CodeGen/microsoft-no-common-align.c @@ -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