* rtl.h (truncated_to_mode): Declare it.

	(struct rtl_hooks): Add reg_truncated_to_mode hook.
	* rtlhooks-def.h (RTL_HOOKS_REG_TRUNCATED_TO_MODE): New macro.
	(RTL_HOOKS_INITIALIZER): Include it.
	* rtlhooks.c (reg_truncated_to_mode_general): New function.
	* combine.c (RTL_HOOKS_REG_TRUNCATED_TO_MODE): Override to
	reg_truncated_to_mode.
	* rtlanal.c (truncated_to_mode): Define it.
	* simplify-rtx.c (simplify_unary_operation_1): Use it.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@111573 138bc75d-0d04-0410-961f-82ee72b054a4

7 files changed, 49 insertions, 8 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7ba31346670..d37067c1142 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2006-02-28  Paolo Bonzini  <bonzini@gnu.org>
+	    Adam Nemet  <anemet@caviumnetworks.com>
+
+	* rtl.h (truncated_to_mode): Declare it.
+	(struct rtl_hooks): Add reg_truncated_to_mode hook.
+	* rtlhooks-def.h (RTL_HOOKS_REG_TRUNCATED_TO_MODE): New macro.
+	(RTL_HOOKS_INITIALIZER): Include it.
+	* rtlhooks.c (reg_truncated_to_mode_general): New function.
+	* combine.c (RTL_HOOKS_REG_TRUNCATED_TO_MODE): Override to
+	reg_truncated_to_mode.
+	* rtlanal.c (truncated_to_mode): Define it.
+	* simplify-rtx.c (simplify_unary_operation_1): Use it.
+
 2006-02-28  Jeff Law  <law@redhat.com>
 
 	* tree-chrec.c (chrec_convert_aggressive): Do not eliminate
diff --git a/gcc/combine.c b/gcc/combine.c
index 443b429976e..32d3f67df4f 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -457,6 +457,9 @@ static rtx gen_lowpart_or_truncate (enum machine_mode, rtx);
 #undef RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES
 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES  reg_num_sign_bit_copies_for_combine
 
+#undef RTL_HOOKS_REG_TRUNCATED_TO_MODE
+#define RTL_HOOKS_REG_TRUNCATED_TO_MODE    reg_truncated_to_mode
+
 static const struct rtl_hooks combine_rtl_hooks = RTL_HOOKS_INITIALIZER;
 
 
diff --git a/gcc/rtl.h b/gcc/rtl.h
index 6e17a224621..9c088e92598 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -1047,6 +1047,7 @@ extern unsigned int subreg_regno (rtx);
 extern unsigned HOST_WIDE_INT nonzero_bits (rtx, enum machine_mode);
 extern unsigned int num_sign_bit_copies (rtx, enum machine_mode);
 extern bool constant_pool_constant_p (rtx);
+extern bool truncated_to_mode (enum machine_mode, rtx);
 
 
 /* 1 if RTX is a subreg containing a reg that is already known to be
@@ -2277,8 +2278,9 @@ struct rtl_hooks
 			   unsigned HOST_WIDE_INT, unsigned HOST_WIDE_INT *);
   rtx (*reg_num_sign_bit_copies) (rtx, enum machine_mode, rtx, enum machine_mode,
 				  unsigned int, unsigned int *);
+  bool (*reg_truncated_to_mode) (enum machine_mode, rtx);
 
-  /* Whenever you add entries here, make sure you adjust hosthooks-def.h.  */
+  /* Whenever you add entries here, make sure you adjust rtlhooks-def.h.  */
 };
 
 /* Each pass can provide its own.  */
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index d8c9fb8a1bf..bbf7e71bf73 100644
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -4808,6 +4808,16 @@ get_condition (rtx jump, rtx *earliest, int allow_cc_mode, int valid_at_insn_p)
 				 allow_cc_mode, valid_at_insn_p);
 }
 
+/* Suppose that truncation from the machine mode of X to MODE is not a
+   no-op.  See if there is anything special about X so that we can
+   assume it already contains a truncated value of MODE.  */
+
+bool
+truncated_to_mode (enum machine_mode mode, rtx x)
+{
+  return REG_P (x) && rtl_hooks.reg_truncated_to_mode (mode, x);
+}
+
 
 /* Initialize non_rtx_starting_operands, which is used to speed up
    for_each_rtx.  */
diff --git a/gcc/rtlhooks-def.h b/gcc/rtlhooks-def.h
index b6c07fb76c1..748666c2dd0 100644
--- a/gcc/rtlhooks-def.h
+++ b/gcc/rtlhooks-def.h
@@ -27,6 +27,7 @@ Boston, MA 02110-1301, USA.  */
 #define RTL_HOOKS_GEN_LOWPART_NO_EMIT gen_lowpart_no_emit_general
 #define RTL_HOOKS_REG_NONZERO_REG_BITS reg_nonzero_bits_general
 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES reg_num_sign_bit_copies_general
+#define RTL_HOOKS_REG_TRUNCATED_TO_MODE reg_truncated_to_mode_general
 
 /* The structure is defined in rtl.h.  */
 #define RTL_HOOKS_INITIALIZER {			\
@@ -34,6 +35,7 @@ Boston, MA 02110-1301, USA.  */
   RTL_HOOKS_GEN_LOWPART_NO_EMIT,		\
   RTL_HOOKS_REG_NONZERO_REG_BITS,		\
   RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES,		\
+  RTL_HOOKS_REG_TRUNCATED_TO_MODE,		\
 }
 
 extern rtx gen_lowpart_general (enum machine_mode, rtx);
@@ -45,5 +47,6 @@ extern rtx reg_nonzero_bits_general (rtx, enum machine_mode, rtx,
 extern rtx reg_num_sign_bit_copies_general (rtx, enum machine_mode, rtx,
 					    enum machine_mode,
 					    unsigned int, unsigned int *);
+extern bool reg_truncated_to_mode_general (enum machine_mode, rtx);
 
 #endif /* GCC_RTL_HOOKS_DEF_H */
diff --git a/gcc/rtlhooks.c b/gcc/rtlhooks.c
index 0034da783fa..ece7198f9a2 100644
--- a/gcc/rtlhooks.c
+++ b/gcc/rtlhooks.c
@@ -117,6 +117,13 @@ reg_nonzero_bits_general (rtx x ATTRIBUTE_UNUSED,
   return NULL;
 }
 
+bool
+reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
+			       rtx x ATTRIBUTE_UNUSED)
+{
+  return false;
+}
+
 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
    least-significant part of X.
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index e84beda68b4..aded68e52df 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -631,14 +631,17 @@ simplify_unary_operation_1 (enum rtx_code code, enum machine_mode mode, rtx op)
 				   GET_MODE (XEXP (SUBREG_REG (op), 0)));
 
       /* If we know that the value is already truncated, we can
-         replace the TRUNCATE with a SUBREG if TRULY_NOOP_TRUNCATION
-         is nonzero for the corresponding modes.  But don't do this
-         for an (LSHIFTRT (MULT ...)) since this will cause problems
-         with the umulXi3_highpart patterns.  */
-      if (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
+         replace the TRUNCATE with a SUBREG.  Note that this is also
+         valid if TRULY_NOOP_TRUNCATION is false for the corresponding
+         modes we just have to apply a different definition for
+         truncation.  But don't do this for an (LSHIFTRT (MULT ...)) 
+         since this will cause problems with the umulXi3_highpart
+         patterns.  */
+      if ((TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
 				 GET_MODE_BITSIZE (GET_MODE (op)))
-	  && num_sign_bit_copies (op, GET_MODE (op))
-	     >= (unsigned int) (GET_MODE_BITSIZE (mode) + 1)
+	   ? (num_sign_bit_copies (op, GET_MODE (op))
+	      >= (unsigned int) (GET_MODE_BITSIZE (mode) + 1))
+	   : truncated_to_mode (mode, op))
 	  && ! (GET_CODE (op) == LSHIFTRT
 		&& GET_CODE (XEXP (op, 0)) == MULT))
 	return rtl_hooks.gen_lowpart_no_emit (mode, op);