MC/ELF: Allow null values in virtual sections, ELF doesn't use special

directives for putting contents in .bss, for example.

llvm-svn: 111376

llvm/lib/MC/MCAssembler.cpp

@@ -628,8 +628,23 @@ void MCAssembler::WriteSectionData(const MCSectionData *SD,
       switch (it->getKind()) {
       default:
         assert(0 && "Invalid fragment in virtual section!");
+      case MCFragment::FT_Data: {
+        // Check that we aren't trying to write a non-zero contents (or fixups)
+        // into a virtual section. This is to support clients which use standard
+        // directives to fill the contents of virtual sections.
+        MCDataFragment &DF = cast<MCDataFragment>(*it);
+        assert(DF.fixup_begin() == DF.fixup_end() &&
+               "Cannot have fixups in virtual section!");
+        for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
+          assert(DF.getContents()[i] == 0 &&
+                 "Invalid data value for virtual section!");
+        break;
+      }
       case MCFragment::FT_Align:
-        assert(!cast<MCAlignFragment>(it)->getValueSize() &&
+        // Check that we aren't trying to write a non-zero value into a virtual
+        // section.
+        assert((!cast<MCAlignFragment>(it)->getValueSize() ||
+                !cast<MCAlignFragment>(it)->getValue()) &&
                "Invalid align in virtual section!");
         break;
       case MCFragment::FT_Fill:

llvm/test/MC/ELF/bss.ll

@@ -0,0 +1,8 @@
+; RUN: llc -filetype=obj %s -o %t
+; FIXME: Add ELF dumping tool to check results.
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
+target triple = "i386-pc-linux-gnu"
+
+@g0 = global i8* null, align 4             ; <i8**> [#uses=0]
+

llvm/test/MC/ELF/dg.exp

@@ -0,0 +1,5 @@
+load_lib llvm.exp
+
+if { [llvm_supports_target X86] } {
+  RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll}]]
+}