ARM IAS: support .align without parameters

.align is handled specially on certain targets.  .align without any parameters
on ARM indicates a default alignment (4).  Handle the special case in the target
parser, but fall back to the generic parser for the normal version.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201988 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@@ -228,6 +228,7 @@ class ARMAsmParser : public MCTargetAsmParser {
   bool parseDirectiveMovSP(SMLoc L);
   bool parseDirectiveObjectArch(SMLoc L);
   bool parseDirectiveArchExtension(SMLoc L);
+  bool parseDirectiveAlign(SMLoc L);
 
   StringRef splitMnemonic(StringRef Mnemonic, unsigned &PredicationCode,
                           bool &CarrySetting, unsigned &ProcessorIMod,
@@ -8022,6 +8023,8 @@ bool ARMAsmParser::ParseDirective(AsmToken DirectiveID) {
     return parseDirectiveObjectArch(DirectiveID.getLoc());
   else if (IDVal == ".arch_extension")
     return parseDirectiveArchExtension(DirectiveID.getLoc());
+  else if (IDVal == ".align")
+    return parseDirectiveAlign(DirectiveID.getLoc());
   return true;
 }
 
@@ -9061,6 +9064,23 @@ bool ARMAsmParser::parseDirectiveObjectArch(SMLoc L) {
   return false;
 }
 
+/// parseDirectiveAlign
+///   ::= .align
+bool ARMAsmParser::parseDirectiveAlign(SMLoc L) {
+  // NOTE: if this is not the end of the statement, fall back to the target
+  // agnostic handling for this directive which will correctly handle this.
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return true;
+
+  // '.align' is target specifically handled to mean 2**2 byte alignment.
+  if (getStreamer().getCurrentSection().first->UseCodeAlign())
+    getStreamer().EmitCodeAlignment(4, 0);
+  else
+    getStreamer().EmitValueToAlignment(4, 0, 1, 0);
+
+  return false;
+}
+
 /// Force static initialization.
 extern "C" void LLVMInitializeARMAsmParser() {
   RegisterMCAsmParser<ARMAsmParser> X(TheARMTarget);

test/MC/ARM/directive-align.s

@@ -0,0 +1,28 @@
+@ RUN: llvm-mc -triple armv7-eabi %s | FileCheck %s
+
+	.data
+
+unaligned:
+	.byte 1
+	.align
+
+@ CHECK-LABEL: unaligned
+@ CHECK-NEXT:	.byte 1
+@ CHECK-NEXT:	.align 2
+
+aligned:
+	.long 0x1d10c1e5
+	.align
+
+@ CHECK-LABEL: aligned
+@ CHECK-NEXT:	.long 487637477
+@ CHECK-NEXT:	.align 2
+
+trailer:
+	.long 0xd1ab011c
+	.align 2
+
+@ CHECK-LABEL: trailer
+@ CHECK-NEXT:	.long 3517645084
+@ CHECK-NEXT:	.align 2
+