[PATCH 07/28] COFF: Don't oversize COMMON symbols when targeting BFD ld

[Aaron Watry]

From: David Majnemer <david.majnemer at gmail.com>

COFF normally doesn't allow us to describe the alignment of COMMON
symbols.

It turns out that most linkers use the symbol size as a hint as to how
aligned the symbol should be.

However the BFD folks have added a .drectve command, which we
now support as of r219229, that allows us to specify the alignment
precisely.  With this in mind, stop rounding sizes up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219281 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/WinCOFFStreamer.cpp | 9 ++++-----
 test/MC/COFF/comm-align.s  | 9 ++++++++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/MC/WinCOFFStreamer.cpp b/lib/MC/WinCOFFStreamer.cpp
index 9bae537..b8d5f2a 100644
--- a/lib/MC/WinCOFFStreamer.cpp
+++ b/lib/MC/WinCOFFStreamer.cpp
@@ -185,14 +185,13 @@ void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
          "Got non-COFF section in the COFF backend!");
 
   const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
-  if (T.isKnownWindowsMSVCEnvironment())
+  if (T.isKnownWindowsMSVCEnvironment()) {
     if (ByteAlignment > 32)
       report_fatal_error("alignment is limited to 32-bytes");
 
-  // Round size up to alignment so that we will honor the alignment request.
-  // TODO: We don't need to do this if we are targeting the bfd linker once we
-  // add support for adding -aligncomm into the .drectve section.
-  Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
+    // Round size up to alignment so that we will honor the alignment request.
+    Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
+  }
 
   AssignSection(Symbol, nullptr);
 
diff --git a/test/MC/COFF/comm-align.s b/test/MC/COFF/comm-align.s
index e658c56..ca6bfbe 100644
--- a/test/MC/COFF/comm-align.s
+++ b/test/MC/COFF/comm-align.s
@@ -24,6 +24,8 @@ _a:
 	.comm _s_4,4,2                  # @s_3
 	.comm _s_8,4,3                  # @s_4
 
+	.comm _small_but_overaligned,1,3                  # @s_4
+
 	.text
 
 	.def _b
@@ -41,10 +43,15 @@ _b:
 # CHECK:     Section: .text (1)
 # CHECK:   }
 # CHECK:   Symbol {
+# CHECK:     Name: _small_but_overaligned
+# CHECK-NEXT:Value: 1
+# CHECK-NEXT:Section: IMAGE_SYM_UNDEFINED (0)
+# CHECK:   }
+# CHECK:   Symbol {
 # CHECK:     Name: _b
 # CHECK:     Section: .text (1)
 # CHECK:   }
 # CHECK: ]
 
-# CHECK: Directive(s): -aligncomm:"_s_2",1 -aligncomm:"_s_4",2 -aligncomm:"_s_8",3
+# CHECK: Directive(s): -aligncomm:"_s_2",1 -aligncomm:"_s_4",2 -aligncomm:"_s_8",3 -aligncomm:"_small_but_overaligned",3
 
-- 
2.1.0