Add ".dword" directive

[void]

Summary

The ".dword" directive is a synonym for ".xword" and is used used
by klibc, a minimalistic libc subset for initramfs.

[void]

This is the doc saying dword == xword:

http://www.rowleydownload.co.uk/arm/documentation/gnu/as/AArch64-Directives.html

[t.p.northover]

Could you add a test?

[nickdesaulniers]

lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

244

Maybe add a . before the [dx]?

[void]

Add testcase.

[void]

In D61719#1496270, @t.p.northover wrote:

Could you add a test?

Done.

[nickdesaulniers]

test/MC/AArch64/size-directive.s

25 ↗

(On Diff #198900)

preceding space?

[void]

Remove errant space.

lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

AArch64AsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
                    const MCInstrInfo &MII, const MCTargetOptions &Options)
     : MCTargetAsmParser(Options, STI, MII) {
     IsILP32 = Options.getABIName() == "ilp32";
     MCAsmParserExtension::Initialize(Parser);
     MCStreamer &S = getParser().getStreamer();
     if (S.getTargetStreamer() == nullptr)
       new AArch64TargetStreamer(S);
 
-    // Alias .hword/.word/xword to the target-independent .2byte/.4byte/.8byte
-    // directives as they have the same form and semantics:
-    ///  ::= (.hword | .word | .xword ) [ expression (, expression)* ]
+    // Alias .hword/.word/[dx]word to the target-independent
+    // .2byte/.4byte/.8byte directives as they have the same form and
+    // semantics:
+    ///  ::= (.hword | .word | .dword | .xword ) [ expression (, expression)* ]
     Parser.addAliasForDirective(".hword", ".2byte");
     Parser.addAliasForDirective(".word", ".4byte");
+    Parser.addAliasForDirective(".dword", ".8byte");
     Parser.addAliasForDirective(".xword", ".8byte");
 
     // Initialize the set of available features.
     setAvailableFeatures(ComputeAvailableFeatures(getSTI().getFeatureBits()));
   }
 
   bool regsEqual(const MCParsedAsmOperand &Op1,
                  const MCParsedAsmOperand &Op2) const override;