[PATCH] Add support for assigning to . in AsmParser

[Anders Waldenborg]

  Updated as per compnerd's comment.

Hi grosbach, dwmw2,

http://llvm-reviews.chandlerc.com/D2625

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D2625?vs=6675&id=6691#toc

Files:
  lib/MC/MCParser/AsmParser.cpp
  test/MC/AsmParser/dot-symbol-assignment-backwards.s
  test/MC/AsmParser/dot-symbol-assignment.s
  test/MC/AsmParser/dot-symbol-non-absolute.s
  test/MC/AsmParser/dot-symbol.s
  test/MC/ELF/dot-symbol-assignment.s

Index: lib/MC/MCParser/AsmParser.cpp
===================================================================
--- lib/MC/MCParser/AsmParser.cpp
+++ lib/MC/MCParser/AsmParser.cpp
@@ -2096,12 +2096,6 @@
   if (Lexer.isNot(AsmToken::EndOfStatement))
     return TokError("unexpected token in assignment");
 
-  // Error on assignment to '.'.
-  if (Name == ".") {
-    return Error(EqualLoc, ("assignment to pseudo-symbol '.' is unsupported "
-                            "(use '.space' or '.org').)"));
-  }
-
   // Eat the end of statement marker.
   Lex();
 
@@ -2129,10 +2123,15 @@
 
     // Don't count these checks as uses.
     Sym->setUsed(false);
-  } else
+  } else if (Name == ".") {
+    if (Out.EmitValueToOffset(Value, 0)) {
+      Error(EqualLoc, "expected assembly-time absolute expression in assignment to pseudo-symbol '.'");
+      eatToEndOfStatement();
+    }
+    return false;
+  } else {
     Sym = getContext().GetOrCreateSymbol(Name);
-
-  // FIXME: Handle '.'.
+  }
 
   // Do the assignment.
   Out.EmitAssignment(Sym, Value);
Index: test/MC/AsmParser/dot-symbol-assignment-backwards.s
===================================================================
--- /dev/null
+++ test/MC/AsmParser/dot-symbol-assignment-backwards.s
@@ -0,0 +1,12 @@
+# RUN: not llvm-mc -filetype=obj -triple i386-unknown-unknown %s 2> %t
+# RUN: FileCheck -input-file %t %s
+
+. = 0x10
+	.byte 1
+
+. = . + 10
+	.byte 2
+
+# CHECK: LLVM ERROR: invalid .org offset '24' (at offset '28')
+. = 0x18
+	.byte 3
Index: test/MC/AsmParser/dot-symbol-assignment.s
===================================================================
--- /dev/null
+++ test/MC/AsmParser/dot-symbol-assignment.s
@@ -0,0 +1,31 @@
+# RUN: llvm-mc -triple i386-unknown-unknown %s | FileCheck %s
+
+	.extern	start
+
+# CHECK: .org 1024, 0
+. = 0x400
+	lgdt	0x400 + 0x100
+
+	ljmpl	$0x08, $(0x400 + 0x150)
+
+
+# CHECK: .org 1280, 0
+. = 0x400 + 0x100
+	.word	(3*8)-1
+	.quad	(0x400 + 0x110)
+
+# CHECK: .org 1296, 0
+. = 0x400 + 0x110
+	.quad	0x0
+	.quad	0x0020980000000000
+	.quad	0x0000900000000000
+
+	.code64
+
+# CHECK: .org 1360, 0
+. = 0x400 + 0x150
+	movabsq	$start, %rcx
+	jmp	*%rcx
+
+
+. = 0x300
Index: test/MC/AsmParser/dot-symbol-non-absolute.s
===================================================================
--- /dev/null
+++ test/MC/AsmParser/dot-symbol-non-absolute.s
@@ -0,0 +1,9 @@
+# RUN: not llvm-mc -filetype=obj -triple i386-unknown-unknown %s 2> %t
+# RUN: FileCheck -input-file %t %s
+
+
+	.extern foo
+
+# CHECK: error: expected assembly-time absolute expression in assignment to pseudo-symbol
+. = foo + 10
+	.byte 1
Index: test/MC/AsmParser/dot-symbol.s
===================================================================
--- test/MC/AsmParser/dot-symbol.s
+++ test/MC/AsmParser/dot-symbol.s
@@ -1,12 +1,9 @@
 # Historically 'as' treats '.' as a reference to the current location in
-# arbitrary contects. We don't support this in general.
+# arbitrary contexts. We don't support this in general.
 
 # RUN: not llvm-mc -triple i386-unknown-unknown %s 2> %t
 # RUN: FileCheck -input-file %t %s
 
-# CHECK: assignment to pseudo-symbol '.' is unsupported (use '.space' or '.org').
-. = . + 8
-
 # CHECK: invalid use of pseudo-symbol '.' as a label
 .:
         .long 0
Index: test/MC/ELF/dot-symbol-assignment.s
===================================================================
--- /dev/null
+++ test/MC/ELF/dot-symbol-assignment.s
@@ -0,0 +1,22 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -sections -section-data | FileCheck %s
+
+one:
+	.quad 0xffffffffffffffff
+
+. = . + 16
+two:
+	.quad 0xeeeeeeeeeeeeeeee
+
+. = 0x20
+three:
+	.quad 0xdddddddddddddddd
+
+// CHECK:        Section {
+// CHECK:          Name: .text
+// CHECK-NEXT:     Type:
+// CHECK-NEXT:     Flags [
+// CHECK:          SectionData (
+// CHECK-NEXT:     0000: FFFFFFFF FFFFFFFF 00000000 00000000
+// CHECK-NEXT:     0010: 00000000 00000000 EEEEEEEE EEEEEEEE
+// CHECK-NEXT:     0020: DDDDDDDD DDDDDDDD
+// CHECK-NEXT:     )
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