* slightly optimized ppc jumptable code (one compare+jump replaced

    by a subtraction)

git-svn-id: trunk@8283 -

compiler/ppcgen/ngppcset.pas

@@ -101,19 +101,23 @@ implementation
           end;
 
       begin
-        if not(jumptable_no_range) then
-          begin
-             { case expr less than min_ => goto elselabel }
-             cg.a_cmp_const_reg_label(current_asmdata.CurrAsmList,opsize,jmp_lt,aint(min_),hregister,elselabel);
-             { case expr greater than max_ => goto elselabel }
-             cg.a_cmp_const_reg_label(current_asmdata.CurrAsmList,opsize,jmp_gt,aint(max_),hregister,elselabel);
-          end;
-        current_asmdata.getjumplabel(table);
+        last:=min_;
         { make it a 32bit register }
         // allocate base and index registers register
         indexreg:= cg.makeregsize(current_asmdata.CurrAsmList, hregister, OS_INT);
         { indexreg := hregister; }
         cg.a_load_reg_reg(current_asmdata.CurrAsmList, opsize, OS_INT, hregister, indexreg);
+        if not(jumptable_no_range) then
+          begin
+             { use aword(value-min)<aword(max-min) instead of two comparisons }
+             { case expr outside min_ .. max_ => goto elselabel               }
+             cg.a_op_const_reg(current_asmdata.CurrAsmList,OP_SUB,OS_INT,aint(min_),indexreg);
+             { this trick requires an unsigned comparison in all cases }
+             cg.a_cmp_const_reg_label(current_asmdata.CurrAsmList,OS_INT,OC_A,aint(max_)-aint(min_),indexreg,elselabel);
+             { already taken into account now }
+             min_:=0;
+          end;
+        current_asmdata.getjumplabel(table);
         { create reference, indexreg := indexreg * sizeof(OS_ADDR) }
         cg.a_op_const_reg(current_asmdata.CurrAsmList, OP_MUL, OS_INT, tcgsize2size[OS_ADDR], indexreg);
         reference_reset_symbol(href, table, (-aint(min_)) * tcgsize2size[OS_ADDR]);
@@ -127,7 +131,6 @@ implementation
         { generate jump table }
         new_section(current_procinfo.aktlocaldata,sec_rodata,current_procinfo.procdef.mangledname,sizeof(aint));
         current_procinfo.aktlocaldata.concat(Tai_label.Create(table));
-        last:=min_;
         genitem(current_procinfo.aktlocaldata,hp);
       end;