[PATCH] ARM IAS: support .even directive

[Saleem Abdulrasool]

Hi rengolin,

The .even directive aligns content to an evan-numbered address.  This is an ARM
specific directive applicable to any section.

http://llvm-reviews.chandlerc.com/D2465

Files:
  lib/Target/ARM/AsmParser/ARMAsmParser.cpp
  test/MC/ARM/directive-even.s

Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -31,6 +31,7 @@
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmParser.h"
 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
@@ -227,6 +228,7 @@
   bool parseDirectiveRegSave(SMLoc L, bool IsVector);
   bool parseDirectiveInst(SMLoc L, char Suffix = '\0');
   bool parseDirectiveLtorg(SMLoc L);
+  bool parseDirectiveEven(SMLoc L);
 
   StringRef splitMnemonic(StringRef Mnemonic, unsigned &PredicationCode,
                           bool &CarrySetting, unsigned &ProcessorIMod,
@@ -7912,6 +7914,8 @@
     parseDirectiveInst(DirectiveID.getLoc(), 'w');
   else if (IDVal == ".ltorg" || IDVal == ".pool")
     parseDirectiveLtorg(DirectiveID.getLoc());
+  else if (IDVal == ".even")
+    parseDirectiveEven(DirectiveID.getLoc());
   else
     return true;
   return false;
@@ -8498,6 +8502,27 @@
   return false;
 }
 
+bool ARMAsmParser::parseDirectiveEven(SMLoc L) {
+  const MCSection *Section = getStreamer().getCurrentSection().first;
+
+  if (getLexer().isNot(AsmToken::EndOfStatement)) {
+    TokError("unexpected token in directive");
+    return false;
+  }
+
+  if (!Section) {
+    getStreamer().InitToTextSection();
+    Section = getStreamer().getCurrentSection().first;
+  }
+
+  if (Section->UseCodeAlign())
+    getStreamer().EmitCodeAlignment(2, 0);
+  else
+    getStreamer().EmitValueToAlignment(2, 0, 1, 0);
+
+  return false;
+}
+
 /// Force static initialization.
 extern "C" void LLVMInitializeARMAsmParser() {
   RegisterMCAsmParser<ARMAsmParser> X(TheARMTarget);
Index: test/MC/ARM/directive-even.s
===================================================================
--- /dev/null
+++ test/MC/ARM/directive-even.s
@@ -0,0 +1,70 @@
+@ RUN: llvm-mc -triple armv7-eabi -filetype obj -o - %s | llvm-readobj -s -sd \
+@ RUN:   | FileCheck %s
+
+	.syntax unified
+
+	.text
+
+	.even
+
+	.global aligned_function
+	.type aligned_function,%function
+aligned_function:
+	bkpt
+
+	.space 5
+
+	.even
+
+	.global unaligned_function
+	.type unaligned_function,%function
+unaligned_function:
+	bkpt
+
+@ CHECK: Section {
+@ CHECK:   Name: .text
+@ CHECK:   SectionData (
+@ CHECK:     0000: 700020E1 00000000 00007000 20E1
+@ CHECK:   )
+@ CHECK: }
+
+	.data
+
+	.space 15
+
+	.even
+
+	.global classifiable
+	.type classifiable,%object
+classifiable:
+	.byte 0xf1
+	.byte 0x51
+	.byte 0xa5
+	.byte 0xc1
+	.byte 0x00
+	.byte 0x00
+	.byte 0x1e
+	.byte 0xab
+
+	.even
+
+	.global declassified
+	.type declassified,%object
+declassified:
+	.byte 0x51
+	.byte 0xa5
+	.byte 0xc1
+	.byte 0xde
+	.byte 0x00
+	.byte 0x00
+	.byte 0xed
+	.byte 0xf1
+
+@ CHECK: Section {
+@ CHECK:   Name: .data
+@ CHECK:   SectionData (
+@ CHECK:     0000: 00000000 00000000 00000000 00000000
+@ CHECK:     0010: F151A5C1 00001EAB 51A5C1DE 0000EDF1
+@ CHECK:   )
+@ CHECK: }
+
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