re PR rtl-optimization/3756 (gcc wishlist: arithmetic right shift for ternary operator)

	PR optimization/3756
	* config/i386/i386.c (ix86_expand_int_movcc): Optimize
	x = ((int) y < 0) ? cst1 : cst2.

From-SVN: r52539

2 files changed, 105 insertions, 13 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fc37d48..b9dee8f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2002-04-19  Jakub Jelinek  <jakub@redhat.com>
 
+	PR optimization/3756
+	* config/i386/i386.c (ix86_expand_int_movcc): Optimize
+	x = ((int) y < 0) ? cst1 : cst2.
+
+2002-04-19  Jakub Jelinek  <jakub@redhat.com>
+
 	PR c/6358
 	* function.c: Reapply patch for c/6358.
 	(expand_function_end): Copy decl_rtl's mode, not
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 275a465..41ec025 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -8131,6 +8131,61 @@ ix86_expand_int_movcc (operands)
 	      code = reverse_condition (code);
 	    }
 	}
+
+      compare_code = NIL;
+      if (GET_MODE_CLASS (GET_MODE (ix86_compare_op0)) == MODE_INT
+	  && GET_CODE (ix86_compare_op1) == CONST_INT)
+	{
+	  if (ix86_compare_op1 == const0_rtx
+	      && (code == LT || code == GE))
+	    compare_code = code;
+	  else if (ix86_compare_op1 == constm1_rtx)
+	    {
+	      if (code == LE)
+		compare_code = LT;
+	      else if (code == GT)
+		compare_code = GE;
+	    }
+	}
+
+      /* Optimize dest = (op0 < 0) ? -1 : cf.  */
+      if (compare_code != NIL
+	  && GET_MODE (ix86_compare_op0) == GET_MODE (out)
+	  && (cf == -1 || ct == -1))
+	{
+	  /* If lea code below could be used, only optimize
+	     if it results in a 2 insn sequence.  */
+
+	  if (! (diff == 1 || diff == 2 || diff == 4 || diff == 8
+		 || diff == 3 || diff == 5 || diff == 9)
+	      || (compare_code == LT && ct == -1)
+	      || (compare_code == GE && cf == -1))
+	    {
+	      /*
+	       * notl op1	(if necessary)
+	       * sarl $31, op1
+	       * orl cf, op1
+	       */
+	      if (ct != -1)
+		{
+		  cf = ct;
+	  	  ct = -1;
+		  code = reverse_condition (code);
+		}
+
+	      out = emit_store_flag (out, code, ix86_compare_op0,
+				     ix86_compare_op1, VOIDmode, 0, -1);
+
+	      out = expand_simple_binop (mode, IOR,
+					 out, GEN_INT (cf),
+					 out, 1, OPTAB_DIRECT);
+	      if (out != operands[0])
+		emit_move_insn (operands[0], out);
+
+	      return 1; /* DONE */
+	    }
+	}
+
       if ((diff == 1 || diff == 2 || diff == 4 || diff == 8
 	   || diff == 3 || diff == 5 || diff == 9)
 	  && (mode != DImode || x86_64_sign_extended_value (GEN_INT (cf))))
@@ -8223,27 +8278,58 @@ ix86_expand_int_movcc (operands)
 	      ct = cf;
 	      cf = 0;
 	      if (FLOAT_MODE_P (GET_MODE (ix86_compare_op0)))
+		/* We may be reversing unordered compare to normal compare,
+		   that is not valid in general (we may convert non-trapping
+		   condition to trapping one), however on i386 we currently
+		   emit all comparisons unordered.  */
+		code = reverse_condition_maybe_unordered (code);
+	      else
+		{
+		  code = reverse_condition (code);
+		  if (compare_code != NIL)
+		    compare_code = reverse_condition (compare_code);
+		}
+	    }
+
+	  if (compare_code != NIL)
+	    {
+	      /* notl op1	(if needed)
+		 sarl $31, op1
+		 andl (cf-ct), op1
+	 	 addl ct, op1
+
+		 For x < 0 (resp. x <= -1) there will be no notl,
+		 so if possible swap the constants to get rid of the
+		 complement.
+		 True/false will be -1/0 while code below (store flag
+		 followed by decrement) is 0/-1, so the constants need
+		 to be exchanged once more.  */
+
+	      if (compare_code == GE || !cf)
 		{
-		  /* We may be reversing unordered compare to normal compare,
-		     that is not valid in general (we may convert non-trapping
-		     condition to trapping one), however on i386 we currently
-		     emit all comparisons unordered.  */
-		  compare_code = reverse_condition_maybe_unordered (compare_code);
-		  code = reverse_condition_maybe_unordered (code);
+	  	  code = reverse_condition (code);
+		  compare_code = LT;
 		}
 	      else
 		{
-		  compare_code = reverse_condition (compare_code);
-		  code = reverse_condition (code);
+		  HOST_WIDE_INT tmp = cf;
+	  	  cf = ct;
+		  ct = tmp;
 		}
+
+	      out = emit_store_flag (out, code, ix86_compare_op0,
+				     ix86_compare_op1, VOIDmode, 0, -1);
 	    }
+	  else
+	    {
+	      out = emit_store_flag (out, code, ix86_compare_op0,
+				     ix86_compare_op1, VOIDmode, 0, 1);
 
-	  out = emit_store_flag (out, code, ix86_compare_op0,
-				 ix86_compare_op1, VOIDmode, 0, 1);
+	      out = expand_simple_binop (mode, PLUS,
+					 out, constm1_rtx,
+					 out, 1, OPTAB_DIRECT);
+	    }
 
-	  out = expand_simple_binop (mode, PLUS,
-				     out, constm1_rtx,
-				     out, 1, OPTAB_DIRECT);
 	  out = expand_simple_binop (mode, AND,
 				     out,
 				     gen_int_mode (cf - ct, mode),