i386.c (test splitter): Narrow tests vs paradoxical subregs.

        * i386.c (test splitter): Narrow tests vs paradoxical subregs.
        (jcc splitters): Add two splitters to simplify compound compares
        that simplify_comparison can't handle.

From-SVN: r46178

2 files changed, 77 insertions, 15 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 90ff4bc..5e491e99 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,10 @@
 2001-10-10  Richard Henderson  <rth@redhat.com>
 
-        * combine.c (try_combine): Handle a SEQUENCE of one insn.
+	* combine.c (try_combine): Handle a SEQUENCE of one insn.
+
+	* i386.c (test splitter): Narrow tests vs paradoxical subregs.
+	(jcc splitters): Add two splitters to simplify compound compares
+	that simplify_comparison can't handle.
 
 2001-10-10  Richard Henderson  <rth@redhat.com>
 
@@ -301,8 +305,8 @@ Wed Oct 10 00:41:29 EDT 2001  John Wehle  (john@feith.com)
 
 2001-10-08  Richard Henderson  <rth@redhat.com>
 
-        * i386.md (movsi_xor): Export.
-        (setcc peep2): Use it when available; add an alternative to
+	* i386.md (movsi_xor): Export.
+	(setcc peep2): Use it when available; add an alternative to
 	match zero_extendhisi2_and.
 
 2001-10-08  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
@@ -533,7 +537,7 @@ Sat Oct  6 07:42:39 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 2001-10-06  Ulrich Weigand  <uweigand@de.ibm.com>
  
-        * config/s390/s390.c (s390_va_arg): Use set_mem_alias_set.
+	* config/s390/s390.c (s390_va_arg): Use set_mem_alias_set.
 
 2001-10-05  Joseph S. Myers  <jsm28@cam.ac.uk>
 
@@ -541,15 +545,15 @@ Sat Oct  6 07:42:39 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 2001-10-05  Catherine Moore  <clm@redhat.com>
 
-        * config/stormy16/stormy-abi:  Document abi changes.
-        * config/stormy16/stormy16.h (REG_ALLOC_ORDER): Redefine.
-        (ICALL_REGS): New register class.
-        (NUM_ARGUMENT_REGISTERS): Now 6.
-        (DEFAULT_PCC_STRUCT_RETURN): Don't try to return structs
-        in registers.
-        (REG_CLASS_FROM_LETTER): Map 'z' to ICALL_REGS.
-        * config/stormy16.md (call_internal, call_value_internal,
-        indirect_jump): Use new 'z' constraint.
+	* config/stormy16/stormy-abi:  Document abi changes.
+	* config/stormy16/stormy16.h (REG_ALLOC_ORDER): Redefine.
+	(ICALL_REGS): New register class.
+	(NUM_ARGUMENT_REGISTERS): Now 6.
+	(DEFAULT_PCC_STRUCT_RETURN): Don't try to return structs
+	in registers.
+	(REG_CLASS_FROM_LETTER): Map 'z' to ICALL_REGS.
+	* config/stormy16.md (call_internal, call_value_internal,
+	indirect_jump): Use new 'z' constraint.
 
 2001-10-05  Neil Booth  <neil@daikokuya.demon.co.uk>
 
@@ -1055,7 +1059,7 @@ Mon Oct  1 06:43:41 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 	storehps builtins.
 	* doc/extend.texi (Vector Extensions): New node.
 	* doc/invoke.texi (Machine Dependent Options): Add documentation for
-        i386 -mmmx, -msse, -m3dnow.
+	i386 -mmmx, -msse, -m3dnow.
 
 Sat Sep 29 15:08:16 CEST 2001  Jan Hubicka  <jh@suse.cz>
 
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 63fefc8..10c1b35 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -8125,7 +8125,7 @@
   HOST_WIDE_INT len = INTVAL (operands[1]);
   HOST_WIDE_INT pos = INTVAL (operands[2]);
   HOST_WIDE_INT mask;
-  enum machine_mode mode;
+  enum machine_mode mode, submode;
 
   mode = GET_MODE (operands[0]);
   if (GET_CODE (operands[0]) == MEM)
@@ -8138,6 +8138,15 @@
 	  operands[0] = adjust_address (operands[0], mode, 0);
 	}
     }
+  else if (GET_CODE (operands[0]) == SUBREG
+	   && (submode = GET_MODE (SUBREG_REG (operands[0])),
+	       GET_MODE_BITSIZE (mode) > GET_MODE_BITSIZE (submode))
+	   && pos + len <= GET_MODE_BITSIZE (submode))
+    {
+      /* Narrow a paradoxical subreg to prevent partial register stalls.  */
+      mode = submode;
+      operands[0] = SUBREG_REG (operands[0]);
+    }
   else if (mode == HImode && pos + len <= 8)
     {
       /* Small HImode tests can be converted to QImode.  */
@@ -12745,6 +12754,55 @@
 	     (const_int 0)
 	     (const_int 1)))])
 
+;; In general it is not safe to assume too much about CCmode registers,
+;; so simplify-rtx stops when it sees a second one.  Under certain 
+;; conditions this is safe on x86, so help combine not create
+;;
+;;	seta	%al
+;;	testb	%al, %al
+;;	je	Lfoo
+
+(define_split 
+  [(set (pc)
+	(if_then_else (ne (match_operator 0 "ix86_comparison_operator"
+				      [(reg 17) (const_int 0)])
+			  (const_int 0))
+		      (label_ref (match_operand 1 "" ""))
+		      (pc)))]
+  ""
+  [(set (pc)
+	(if_then_else (match_dup 0)
+		      (label_ref (match_dup 1))
+		      (pc)))]
+{
+  PUT_MODE (operands[0], VOIDmode);
+})
+  
+(define_split 
+  [(set (pc)
+	(if_then_else (eq (match_operator 0 "ix86_comparison_operator"
+				      [(reg 17) (const_int 0)])
+			  (const_int 0))
+		      (label_ref (match_operand 1 "" ""))
+		      (pc)))]
+  ""
+  [(set (pc)
+	(if_then_else (match_dup 0)
+		      (label_ref (match_dup 1))
+		      (pc)))]
+{
+  rtx new_op0 = copy_rtx (operands[0]);
+  operands[0] = new_op0;
+  PUT_MODE (new_op0, VOIDmode);
+  PUT_CODE (new_op0, REVERSE_CONDITION (GET_CODE (new_op0),
+					GET_MODE (XEXP (new_op0, 0))));
+
+  /* Make sure that (a) the CCmode we have for the flags is strong
+     enough for the reversed compare or (b) we have a valid FP compare.  */
+  if (! ix86_comparison_operator (new_op0, VOIDmode))
+    FAIL;
+})
+
 ;; Define combination compare-and-branch fp compare instructions to use
 ;; during early optimization.  Splitting the operation apart early makes
 ;; for bad code when we want to reverse the operation.