Correctly align bss.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114556 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCELFStreamer.cpp

@@ -322,9 +322,15 @@ void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                                                     SectionKind::getBSS());
 
     MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
+    new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
+
     MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
     SD.setFragment(F);
     Symbol->setSection(*Section);
+
+    // Update the maximum alignment of the section if necessary.
+    if (ByteAlignment > SectData.getAlignment())
+      SectData.setAlignment(ByteAlignment);
   } else {
     SD.setCommon(Size, ByteAlignment);
   }

test/MC/ELF/align-bss.s

@@ -0,0 +1,17 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | elf-dump  | FileCheck %s
+
+// Test that the bss section is correctly aligned
+
+	.local	foo
+	.comm	foo,2048,16
+
+// CHECK:        ('sh_name', 13) # '.bss'
+// CHECK-NEXT:   ('sh_type', 8)
+// CHECK-NEXT:   ('sh_flags', 3)
+// CHECK-NEXT:   ('sh_addr', 0)
+// CHECK-NEXT:   ('sh_offset', 64)
+// CHECK-NEXT:   ('sh_size', 2048)
+// CHECK-NEXT:   ('sh_link', 0)
+// CHECK-NEXT:   ('sh_info', 0)
+// CHECK-NEXT:   ('sh_addralign', 16)
+// CHECK-NEXT:   ('sh_entsize', 0)