[PATCH] D56391: Limit COFF 'common' emission to <=32 alignment types.

[Erich Keane via Phabricator via cfe-commits]

erichkeane created this revision.
erichkeane added reviewers: majnemer, rnk, pengfei.

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


Repository:
  rC Clang

https://reviews.llvm.org/D56391

Files:
  lib/CodeGen/CodeGenModule.cpp
  test/CodeGen/microsoft-no-common-align.c


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
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;
 }


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