Begin to modernize optimized dispatch. (#271)

This feature was controlled by the compilation flag `OPDISP`
which would enable some bits of assembler on the x86 (ISC or DOS)
or some other specialized code on SPARC. On SPARC hardware, there
was a special compilation process that would preprocess the code
and generate dispatch tables.

We do this now when this feature is enabled using gcc's computed
gotos feature. This is available in clang and some other compilers.
Notably, it isn't present in Visual Studio.

This doesn't decrease our portability at all as this feature is
optional and it replaces specialized assembler code with C using
compiler extensions (making it cross-platform).

In doing this, we've removed a bunch of related code, however,
it is likely that other pieces yet remain and will be removed
in subsequent commits as we clean things up and refine them.

This feature remains disabled by default for now.

src/dsp386.il

@@ -119,29 +119,6 @@
 .end
 
 
-.inline fast0_dispatcher,0
-	leal	-1(%edi),%eax
-	xorb	$3,%al
-	movzbl	(%eax),%eax
-	jmp	*optable(,%eax,4)
-.end
-
-.inline fast1_dispatcher,0
-	movl	%edi,%eax
-	xorb	$3,%al
-	movzbl	(%eax),%eax
-	incl	%edi
-	jmp	*optable(,%eax,4)
-.end
-
-.inline fast2_dispatcher,0
-	leal	1(%edi),%eax
-	xorb	$3,%al
-	addl	$2,%edi
-	movzbl	(%eax),%eax
-	jmp	*optable(,%eax,4)
-.end
-
 .inline	plus_err_label,0
 plus_err:
 .end

src/dspSPARC.il

@@ -78,59 +78,6 @@ done:				!		else done;
 .end
 
 
-/* inline dispatching support */
-/* Thanks to Russ Atkinson, December 29, 1987 */
-
-/* To use in compiling XXX, cc -O2 XXX.c dispatch.il */
-
-/* The qdisp* routines depend on pc being in %o0 and table being in %o1 */
-
-.inline	_qdisp0,8
-	! qdisp0 - %o0: pc, %o1: table
-	ldub	[%o0+0],%o2	! temp = *pc
-	sll	%o2,2,%o2	! temp = temp * 4
-	ld	[%o2+%o1],%o2	! temp = table[temp]
-	jmp	%o2		! dispatch
-	nop
-.end
-
-.inline	_qdisp1,8
-	! qdisp1 - %o0: pc, %o1: table
-	ldub	[%o0+1],%o2	! temp = *pc
-	sll	%o2,2,%o2	! temp = temp * 4
-	ld	[%o2+%o1],%o2	! temp = table[temp]
-	jmp	%o2		! dispatch
-	add	%o0,1,%o0	! update the pc
-.end
-
-.inline	_qdisp2,8
-	! qdisp2 - %o0: pc, %o1: table
-	ldub	[%o0+2],%o2	! temp = *pc
-	sll	%o2,2,%o2	! temp = temp * 4
-	ld	[%o2+%o1],%o2	! temp = table[temp]
-	jmp	%o2		! dispatch
-	add	%o0,2,%o0	! update the pc
-.end
-
-.inline	_qdisp3,8
-	! qdisp3 - %o0: pc, %o1: table
-	ldub	[%o0+3],%o2	! temp = *pc
-	sll	%o2,2,%o2	! temp = temp * 4
-	ld	[%o2+%o1],%o2	! temp = table[temp]
-	jmp	%o2		! dispatch
-	add	%o0,3,%o0	! update the pc
-.end
-
-
-.inline	_fast_dispatcher,8
-	!  - %o0: table, %o1: pc
-	ldub	[%o1+0],%o1	! fetch inst byte
-	sll	%o1,2,%o1
-	ld	[%o1+%o0],%o1
-	jmp	%o1		! dispatch
-	nop
-.end
-
 /*
 	***************************************************************
 	Inline Assembly help for dispatcher.

src/dsphack.lex

@@ -1,62 +0,0 @@
-/* @(#) disphack.lex Version 1.5 (11/2/88). copyright envos & Fuji Xerox  */
-
-REG	"%"[oilg][0-9]
-LABEL	L[0-9]+
-COMPUTE	"\tcall\t_compute_dispatch_table,0\n	nop\n\tmov\t%o0,"
-DISPATCH "\tmov\t"{REG}",%o0\n\tcall\t_fast_dispatcher,2\n\tnop\n"
-HEXD	0x[0-3]
-ADDX	"\tadd\t"{REG}","{HEXD}","{REG}
-LDUB	"\tldub\t["{REG}"],"{REG}
-LDUBm1	"\tldub\t["{REG}"+-0x1],%o1"
-MOV	"\tmov\t"{REG}",%o1"
-
-%%
-	extern char *dispatch_label;
-
-
-{COMPUTE}	printf(" set %s,", dispatch_label);
-
-{ADDX}\n{LDUBm1}\n{DISPATCH} {
-	if (    memcmp(yytext + 5, yytext + 13, 3)
-	    ||  memcmp(yytext + 5, yytext + 24, 3)) {REJECT};
-
-	printf(" ldub [%.3s+%.3s+-0x1],%%o1\n",yytext+5, yytext+9);
-	printf(" sll %%o1,2,%%o1\n");
-	printf(" ld [%%o1+%.3s],%%o1\n",yytext+43);
-	printf(" jmp %%o1\n");
-	printf("%.16s\n", yytext);
-}
-
-
-
-{DISPATCH}	{
-	printf(" sll %%o1,2,%%o1\n");
-	printf(" ld [%%o1+%%%.2s],%%o1\n",yytext + 6);
-	printf(" jmp %%o1\n");
-	printf(" nop\n");
-}
-
-{ADDX}\n{LDUB}	{
-	if (   !memcmp(yytext + 5, yytext + 13, 3)
-	    && !memcmp(yytext + 5, yytext + 24, 3)
-	    &&  memcmp(yytext + 5, yytext + 29, 3)) {
-		printf(" ldub [%.3s+%.3s],%.3s\n%.16s\n",
-			 yytext+5,yytext+9,yytext+29,yytext);
-	} else
-		printf("%s", yytext);
-}
-
-
-{LDUB}\n\tcmp\t{REG}",255\n\tbgu\t"{LABEL}\n\t\sll\t{REG}",2,"{REG}\n\tset\t{LABEL}","	{
-	if (memcmp(yytext+yyleng-strlen(dispatch_label)-1,
-			dispatch_label,
-			strlen(dispatch_label))) {
-		fprintf(stderr, "Label in dispatch changed. Edit disphack.lex");
-		fprintf(stderr, " and change '%s' to label", dispatch_label);
-		fprintf(stderr, " in last line of \n\n%s\n\n and retry!\n", yytext);
-		exit(-1);
-	} else if (memcmp(yytext + 12, yytext + 21, 3)) {
-		fprintf(stderr, "Odd sequence %s\n", yytext);
-	};
-	REJECT;
-};

src/find-dsp.lex

@@ -1,17 +0,0 @@
-/* @(#) find-dispatch.lex Version 1.2 (4/7/89). copyright envos & Fuji Xerox  */
-
-REG	"%"[oilg][0-9]
-REGOFF	"%"[oilg][0-9]\+\-0x[0-9]
-LABEL	L[0-9]+
-LDUB	"\tldub\t["{REG}"],"{REG}
-LDUB2	"\tldub\t["{REGOFF}"],"{REG}
-
-%%
-
-{LDUB2}\n\tcmp\t{REG}",255\n\tbgu\t"{LABEL}\n\t\sll\t{REG}",2,"{REG}\n\tset\t	{	char x;
-	printf("char *dispatch_label = \"");
-	loop: x=input();
-	if(x == ','){ printf("\";\n"); return;}
-	output(x); goto loop;}
-
-.*\n	{}