gcse.c (hash_scan_set): Look through REG_EQUAL or REG_EQUIV notes also when doing...

2005-11-24  Paolo Bonzini  <bonzini@gnu.org>

	* gcse.c (hash_scan_set): Look through REG_EQUAL or REG_EQUIV notes
	also when doing PRE, rather than only for global CPROP.

From-SVN: r107456

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 67e050a72e632b8c0ca6e7cc701d87a4c9387533..361250db81231c01644f9411093dfaa9af4ae6fb 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2005-11-24  Paolo Bonzini  <bonzini@gnu.org>
+
+       * gcse.c (hash_scan_set): Look through REG_EQUAL or REG_EQUIV notes
+       also when doing PRE, rather than only for global CPROP.
+
 2005-11-24  Ben Elliston  <bje@au.ibm.com>
 
        * machmode.h (CLASS_HAS_WIDER_MODES_P): New macro.

diff --git a/gcc/gcse.c b/gcc/gcse.c
index 2c74574b4493536535667322d580487f1d19306d..3a53d9e4d26cbc55af2c2b1b61d448a0b4389394 100644 (file)
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -1700,10 +1700,15 @@ hash_scan_set (rtx pat, rtx insn, struct hash_table *table)
       unsigned int regno = REGNO (dest);
       rtx tmp;
 
-      /* If this is a single set and we are doing constant propagation,
-        see if a REG_NOTE shows this equivalent to a constant.  */
-      if (table->set_p && (note = find_reg_equal_equiv_note (insn)) != 0
-         && gcse_constant_p (XEXP (note, 0)))
+      /* See if a REG_NOTE shows this equivalent to a simpler expression.
+        This allows us to do a single GCSE pass and still eliminate
+        redundant constants, addresses or other expressions that are
+        constructed with multiple instructions.  */
+      note = find_reg_equal_equiv_note (insn);
+      if (note != 0
+         && (table->set_p
+             ? gcse_constant_p (XEXP (note, 0))
+             : want_to_gcse_p (XEXP (note, 0))))
        src = XEXP (note, 0), pat = gen_rtx_SET (VOIDmode, dest, src);
 
       /* Only record sets of pseudo-regs in the hash table.  */
@@ -1724,8 +1729,7 @@ hash_scan_set (rtx pat, rtx insn, struct hash_table *table)
             REG_EQUIV notes and if the argument slot is used somewhere
             explicitly, it means address of parameter has been taken,
             so we should not extend the lifetime of the pseudo.  */
-         && ((note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) == 0
-             || ! MEM_P (XEXP (note, 0))))
+         && (note == NULL_RTX || ! MEM_P (XEXP (note, 0))))
        {
          /* An expression is not anticipatable if its operands are
             modified before this insn or if this is not the only SET in