COFF: Fix common symbol alignment.

llvm-svn: 240217

diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
index e6403c2..18963f2 100644 (file)
--- a/lld/COFF/Chunks.cpp
+++ b/lld/COFF/Chunks.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/raw_ostream.h"
+#include <algorithm>
 
 using namespace llvm;
 using namespace llvm::object;
@@ -169,10 +170,9 @@ SectionRef SectionChunk::getSectionRef() {
 }
 
 CommonChunk::CommonChunk(const COFFSymbolRef S) : Sym(S) {
-  // Alignment is a section attribute, but common symbols don't
-  // belong to any section. How do we know common data alignments?
-  // Needs investigating. For now, we set a large number as an alignment.
-  Align = 16;
+  // Common symbols are aligned on natural boundaries up to 32 bytes.
+  // This is what MSVC link.exe does.
+  Align = std::min(uint64_t(32), NextPowerOf2(Sym.getValue()));
 }
 
 uint32_t CommonChunk::getPermissions() const {

diff --git a/lld/test/COFF/common.test b/lld/test/COFF/common.test
index b9c0a2b..b74dffb 100644 (file)
--- a/lld/test/COFF/common.test
+++ b/lld/test/COFF/common.test
@@ -4,7 +4,7 @@
 
 # Operands of B8 (MOV EAX) are common symbols
 CHECK: 3000: b8 00 10 00 40
-CHECK: 3005: b8 10 10 00 40
+CHECK: 3005: b8 04 10 00 40
 CHECK: 300a: b8 20 10 00 40
 CHECK: 300f: b8 60 10 00 40
-CHECK: 3014: b8 70 10 00 40
+CHECK: 3014: b8 80 10 00 40