Jan Hubicka <hubicka@freesoft.cz>

        * i386.md (ffs expander): Emit Pentium friendly code for
        TARGET_PENTIUM.

From-SVN: r29769

gcc/ChangeLog

+Sat Oct  2 10:53:22 1999  Jan Hubicka  <hubicka@freesoft.cz>
+
+	* i386.md (ffs expander): Emit Pentium friendly code for
+	TARGET_PENTIUM.
+
 Sat Oct  2 02:48:21 1999  Mark P. Mitchell  <mark@codesourcery.com>
 
 	* tree.c (build): Don't look at TREE_SIDE_EFFECTS or TREE_RAISES 

gcc/config/i386/i386.md

@@ -6779,6 +6779,57 @@
 				const0_rtx),
 		    tmp,
 		    out)));
+      emit_insn (gen_addsi3 (out, out, const1_rtx));
+      emit_move_insn (operands[0], out);
+    }
+
+  /* Pentium bsf instruction is extremly slow.  Following code is recommended by
+     the Intel Optimizing Manual as resonable replacement:
+           TEST    EAX,EAX
+	   JZ      SHORT BS2
+	   XOR     ECX,ECX
+	   MOV     DWORD PTR [TEMP+4],ECX
+	   SUB     ECX,EAX
+	   AND     EAX,ECX
+	   MOV     DWORD PTR [TEMP],EAX
+	   FILD    QWORD PTR [TEMP]
+	   FSTP    QWORD PTR [TEMP]
+	   WAIT    ; WAIT only needed for compatibility with
+	           ; earlier processors
+	   MOV     ECX, DWORD PTR [TEMP+4]
+	   SHR     ECX,20
+	   SUB     ECX,3FFH
+	   TEST    EAX,EAX       ; clear zero flag
+       BS2:
+     Following piece of code expand ffs to similar beast.
+       */
+
+  else if (TARGET_PENTIUM && !optimize_size && TARGET_80387)
+    {
+      rtx label = gen_label_rtx ();
+      rtx lo, hi;
+      rtx mem = assign_386_stack_local (DImode, 0);
+      rtx fptmp = gen_reg_rtx (DFmode);
+      split_di (&mem, 1, &lo, &hi);
+
+      emit_move_insn (out, const0_rtx);
+
+      emit_cmp_and_jump_insns (in, const0_rtx, EQ, 0, SImode, 1, 0, label);
+
+      emit_move_insn (hi, out);
+      emit_insn (gen_subsi3 (out, out, in));
+      emit_insn (gen_andsi3 (out, out, in));
+      emit_move_insn (lo, out);
+      emit_insn (gen_floatdidf2 (fptmp,mem));
+      emit_move_insn (gen_rtx_MEM (DFmode, XEXP (mem, 0)), fptmp);
+      emit_move_insn (out, hi);
+      emit_insn (gen_lshrsi3 (out, out, GEN_INT (20)));
+      emit_insn (gen_subsi3 (out, out, GEN_INT (0x3fe)));
+
+      emit_label (label);
+      LABEL_NUSES (label) = 1;
+
+      emit_move_insn (operands[0], out);
     }
   else
     {
@@ -6790,10 +6841,9 @@
 			      const0_rtx)));
       emit_insn (gen_negsi2 (tmp, tmp));
       emit_insn (gen_iorsi3 (out, out, tmp));
+      emit_insn (gen_addsi3 (out, out, const1_rtx));
+      emit_move_insn (operands[0], out);
     }
-  emit_insn (gen_addsi3 (out, out, const1_rtx));
-
-  emit_move_insn (operands[0], out);
   DONE;  
 }")