Limit COFF 'common' emission to <=32 alignment types.

[erichkeane]

Summary

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://bugs.llvm.org/show_bug.cgi?id=33035

[majnemer]

lib/CodeGen/CodeGenModule.cpp

3766

I think this should be isKnownWindowsMSVCEnvironment

[pengfei]

LGTM, thanks Erich.

lib/CodeGen/CodeGenModule.cpp

if (const auto *RT = VarType->getAs<RecordType>()) {
           continue;
         if (FD->hasAttr<AlignedAttr>())
           return true;
         if (Context.isAlignmentRequired(FD->getType()))
           return true;
       }
     }
   }
+  // 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;
 }
 
 llvm::GlobalValue::LinkageTypes CodeGenModule::getLLVMLinkageForDeclarator(
     const DeclaratorDecl *D, GVALinkage Linkage, bool IsConstantVariable) {
   if (Linkage == GVA_Internal)
     return llvm::Function::InternalLinkage;

test/CodeGen/microsoft-no-common-align.c

+// 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