Fix printing of alias instructions by removing redundant spacing

[mstojanovic]

Summary

Some alias instructions are printed with with an extra space after the tab character.
Fix this by skipping that space when the tab character is printed so that the instructions are aligned with the rest of the code.

A simple output used to look like this:

 0:	27 bd ff f8 	addiu	$sp, $sp, -8
 4:	af be 00 04 	sw	$fp, 4($sp)
 8:	03 a0 f0 25 	move	 $fp, $sp
 c:	af c0 00 00 	sw	$zero, 0($fp)
10:	10 00 00 01 	b	8 <main+0x18>
14:	00 00 00 00 	nop
18:	24 02 00 00 	addiu	$2, $zero, 0
1c:	03 c0 e8 25 	move	 $sp, $fp
20:	8f be 00 04 	lw	$fp, 4($sp)
24:	27 bd 00 08 	addiu	$sp, $sp, 8
28:	03 e0 00 09 	jr	 $ra
2c:	00 00 00 00 	nop

With the new formatting, it looks like this:

 0:	27 bd ff f8 	addiu	$sp, $sp, -8
 4:	af be 00 04 	sw	$fp, 4($sp)
 8:	03 a0 f0 25 	move	$fp, $sp
 c:	af c0 00 00 	sw	$zero, 0($fp)
10:	10 00 00 01 	b	8 <main+0x18>
14:	00 00 00 00 	nop
18:	24 02 00 00 	addiu	$2, $zero, 0
1c:	03 c0 e8 25 	move	$sp, $fp
20:	8f be 00 04 	lw	$fp, 4($sp)
24:	27 bd 00 08 	addiu	$sp, $sp, 8
28:	03 e0 00 09 	jr	$ra
2c:	00 00 00 00 	nop

[sdardis]

This LGTM, but let's see if @SjoerdMeijer, @olista01 or @stoklund have any concerns.

[sdardis]

Also, you may want to retitle this diff+update summary to reflect it affects the printing of instruction aliases in general, rather than for just mips or when objdump is used..

[SjoerdMeijer]

looks reasonable to me

[sdardis]

Can you retitle this as it's more general than the output of llvm-objdump, i.e. it affects the output of llc and it's not specific?

Otherwise LGTM.

llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp

void AsmWriterEmitter::EmitPrintAliasInstruction(raw_ostream &O) {
   // MCInst.
   O << "  unsigned I = 0;\n";
   O << "  while (AsmString[I] != ' ' && AsmString[I] != '\\t' &&\n";
   O << "         AsmString[I] != '$' && AsmString[I] != '\\0')\n";
   O << "    ++I;\n";
   O << "  OS << '\\t' << StringRef(AsmString, I);\n";
 
   O << "  if (AsmString[I] != '\\0') {\n";
-  O << "    if (AsmString[I] == ' ' || AsmString[I] == '\\t')";
+  O << "    if (AsmString[I] == ' ' || AsmString[I] == '\\t') {\n";
   O << "      OS << '\\t';\n";
+  O << "      ++I;\n";
+  O << "    }\n";
   O << "    do {\n";
   O << "      if (AsmString[I] == '$') {\n";
   O << "        ++I;\n";
   O << "        if (AsmString[I] == (char)0xff) {\n";
   O << "          ++I;\n";
   O << "          int OpIdx = AsmString[I++] - 1;\n";
   O << "          int PrintMethodIdx = AsmString[I++] - 1;\n";
   O << "          printCustomAliasOperand(MI, OpIdx, PrintMethodIdx, ";