[PATCH] Reduce conservativeness in REE using machine model (issue6631066)

[tejohnson at google dot com (Teresa Johnson)]

Revised patch to address conservative behavior in redundant extend
elimination that was resulting in redundant extends not being
removed. Now uses a new target hook machine_mode_from_attr_mode
which is currently enabled only for i386.

Bootstrapped and tested on x86_64-unknown-linux-gnu. Is this ok for trunk?

Thanks,
Teresa

2012-10-11  Teresa Johnson  <tejohnson@google.com>

	* doc/tm.texi: Document TARGET_MACHINE_MODE_FROM_ATTR_MODE.
	* doc/tm.texi.in: Regenerated.
	* targhooks.c (default_machine_mode_from_attr_mode): New function.
	* targhooks.h (default_machine_mode_from_attr_mode): Declare.
	* target.def (machine_mode_from_attr_mode): New target hook.
	* ree.c (get_mode): New function.
	(add_removable_extension): Use get_mode to obtain the
        machine mode for comparison with other extends.
	* config/i386/i386.c (ix86_machine_mode_from_attr_mode): New function.

Index: doc/tm.texi
===================================================================
--- doc/tm.texi	(revision 192265)
+++ doc/tm.texi	(working copy)
@@ -10468,6 +10468,10 @@ In order to enforce the representation of @code{mo
 @code{mode}.
 @end deftypefn
 
+@deftypefn {Target Hook} {enum machine_mode} TARGET_MACHINE_MODE_FROM_ATTR_MODE (rtx @var{insn})
+If @var{insn} has an attr_mode that is equivalent to a @code{machine_mode},  return the corresponding @code{machine_mode}, otherwise return  @code{MAX_MACHINE_MODE}.
+@end deftypefn
+
 @defmac STORE_FLAG_VALUE
 A C expression describing the value returned by a comparison operator
 with an integral mode and stored by a store-flag instruction
Index: doc/tm.texi.in
===================================================================
--- doc/tm.texi.in	(revision 192265)
+++ doc/tm.texi.in	(working copy)
@@ -10326,6 +10326,8 @@ In order to enforce the representation of @code{mo
 @code{mode}.
 @end deftypefn
 
+@hook TARGET_MACHINE_MODE_FROM_ATTR_MODE
+
 @defmac STORE_FLAG_VALUE
 A C expression describing the value returned by a comparison operator
 with an integral mode and stored by a store-flag instruction
Index: targhooks.c
===================================================================
--- targhooks.c	(revision 192265)
+++ targhooks.c	(working copy)
@@ -250,6 +250,14 @@ default_mode_rep_extended (enum machine_mode mode
   return UNKNOWN;
 }
 
+/* The default implementation of TARGET_MACHINE_MODE_FROM_ATTR_MODE.  */
+
+enum machine_mode
+default_machine_mode_from_attr_mode (rtx insn ATTRIBUTE_UNUSED)
+{
+  return MAX_MACHINE_MODE;
+}
+
 /* Generic hook that takes a CUMULATIVE_ARGS pointer and returns true.  */
 
 bool
Index: targhooks.h
===================================================================
--- targhooks.h	(revision 192265)
+++ targhooks.h	(working copy)
@@ -47,6 +47,7 @@ extern unsigned HOST_WIDE_INT default_shift_trunca
   (enum machine_mode);
 extern unsigned int default_min_divisions_for_recip_mul (enum machine_mode);
 extern int default_mode_rep_extended (enum machine_mode, enum machine_mode);
+enum machine_mode default_machine_mode_from_attr_mode (rtx insn);
 
 extern tree default_stack_protect_guard (void);
 extern tree default_external_stack_protect_fail (void);
Index: target.def
===================================================================
--- target.def	(revision 192265)
+++ target.def	(working copy)
@@ -1576,6 +1576,17 @@ DEFHOOK
  int, (enum machine_mode mode, enum machine_mode rep_mode),
  default_mode_rep_extended)
 
+/* If the machine description for an rtl INSN defines the
+   attr_mode, and that mode is equivalent to a machine_mode, return
+   the corresponding machine_mode. Return MAX_MACHINE_MODE otherwise.  */
+DEFHOOK
+(machine_mode_from_attr_mode,
+ "If @var{insn} has an attr_mode that is equivalent to a @code{machine_mode},\
+  return the corresponding @code{machine_mode}, otherwise return\
+  @code{MAX_MACHINE_MODE}.",
+ enum machine_mode, (rtx insn),
+ default_machine_mode_from_attr_mode)
+
 /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 DEFHOOK
 (valid_pointer_mode,
Index: ree.c
===================================================================
--- ree.c	(revision 192265)
+++ ree.c	(working copy)
@@ -756,6 +756,20 @@ combine_reaching_defs (ext_cand *cand, const_rtx s
   return false;
 }
 
+/* Given an INSN, obtain the attr_mode specified by the machine
+   description, and map it to the corresponding machine_mode. If the
+   attr_mode isn't specified, return the machine mode for DEST.  */
+
+static enum machine_mode
+get_mode (rtx insn, rtx dest)
+{
+  enum machine_mode mode;
+  mode = targetm.machine_mode_from_attr_mode(insn);
+  if (mode == MAX_MACHINE_MODE)
+    mode = GET_MODE (dest);
+  return mode;
+}
+
 /* Add an extension pattern that could be eliminated.  */
 
 static void
@@ -775,7 +789,7 @@ add_removable_extension (const_rtx expr, rtx insn,
   src = SET_SRC (expr);
   code = GET_CODE (src);
   dest = SET_DEST (expr);
-  mode = GET_MODE (dest);
+  mode = get_mode (insn, dest);
 
   if (REG_P (dest)
       && (code == SIGN_EXTEND || code == ZERO_EXTEND)
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 192265)
+++ config/i386/i386.c	(working copy)
@@ -15074,6 +15074,48 @@ ix86_print_operand_address (FILE *file, rtx addr)
     }
 }
 
+/* Implementation of TARGET_MACHINE_MODE_FROM_ATTR_MODE.  */
+
+static enum machine_mode
+ix86_machine_mode_from_attr_mode (rtx insn)
+{
+  switch (get_attr_mode (insn))
+    {
+      case MODE_QI:
+        return QImode;
+      case MODE_HI:
+        return HImode;
+      case MODE_SI:
+        return SImode;
+      case MODE_DI:
+        return DImode;
+      case MODE_TI:
+        return TImode;
+      case MODE_OI:
+        return OImode;
+      case MODE_SF:
+        return SFmode;
+      case MODE_DF:
+        return DFmode;
+      case MODE_XF:
+        return XFmode;
+      case MODE_TF:
+        return TFmode;
+      case MODE_V8SF:
+        return V8SFmode;
+      case MODE_V4DF:
+        return V4DFmode;
+      case MODE_V4SF:
+        return V4SFmode;
+      case MODE_V2DF:
+        return V2DFmode;
+      case MODE_V2SF:
+        return V2SFmode;
+      default:
+        return MAX_MACHINE_MODE;
+    }
+}
+
 /* Implementation of TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA.  */
 
 static bool
@@ -41171,6 +41213,9 @@ ix86_memmodel_check (unsigned HOST_WIDE_INT val)
 #undef TARGET_EXPAND_TO_RTL_HOOK
 #define TARGET_EXPAND_TO_RTL_HOOK ix86_maybe_switch_abi
 
+#undef TARGET_MACHINE_MODE_FROM_ATTR_MODE
+#define TARGET_MACHINE_MODE_FROM_ATTR_MODE ix86_machine_mode_from_attr_mode
+
 #undef TARGET_LEGITIMATE_ADDRESS_P
 #define TARGET_LEGITIMATE_ADDRESS_P ix86_legitimate_address_p
 

--
This patch is available for review at http://codereview.appspot.com/6631066