* gcse.c (local_cprop_find_used_regs): New.

        (local_cprop_pass): Use it.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@62555 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 50 insertions, 2 deletions

diff --git a/gcc/gcse.c b/gcc/gcse.c
index 3adaf5ca0ac..2cc7f0b1c67 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -706,6 +706,7 @@ static void free_insn_expr_list_list	PARAMS ((rtx *));
 static void clear_modify_mem_tables	PARAMS ((void));
 static void free_modify_mem_tables	PARAMS ((void));
 static rtx gcse_emit_move_after		PARAMS ((rtx, rtx, rtx));
+static void local_cprop_find_used_regs	PARAMS ((rtx *, void *));
 static bool do_local_cprop		PARAMS ((rtx, rtx, int, rtx*));
 static bool adjust_libcall_notes	PARAMS ((rtx, rtx, rtx, rtx*));
 static void local_cprop_pass		PARAMS ((int));
@@ -4258,6 +4259,53 @@ cprop_insn (insn, alter_jumps)
   return changed;
 }
 
+/* Like find_used_regs, but avoid recording uses that appear in
+   input-output contexts such as zero_extract or pre_dec.  This
+   restricts the cases we consider to those for which local cprop
+   can legitimately make replacements.  */
+
+static void
+local_cprop_find_used_regs (xptr, data)
+     rtx *xptr;
+     void *data;
+{
+  rtx x = *xptr;
+
+  if (x == 0)
+    return;
+
+  switch (GET_CODE (x))
+    {
+    case ZERO_EXTRACT:
+    case SIGN_EXTRACT:
+    case STRICT_LOW_PART:
+      return;
+
+    case PRE_DEC:
+    case PRE_INC:
+    case POST_DEC:
+    case POST_INC:
+    case PRE_MODIFY:
+    case POST_MODIFY:
+      /* Can only legitimately appear this early in the context of
+	 stack pushes for function arguments, but handle all of the
+	 codes nonetheless.  */
+      return;
+
+    case SUBREG:
+      /* Setting a subreg of a register larger than word_mode leaves
+	 the non-written words unchanged.  */
+      if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) > BITS_PER_WORD)
+	return;
+      break;
+
+    default:
+      break;
+    }
+
+  find_used_regs (xptr, data);
+}
+  
 /* LIBCALL_SP is a zero-terminated array of insns at the end of a libcall;
    their REG_EQUAL notes need updating.  */
 
@@ -4413,9 +4461,9 @@ local_cprop_pass (alter_jumps)
 	  do
 	    {
 	      reg_use_count = 0;
-	      note_uses (&PATTERN (insn), find_used_regs, NULL);
+	      note_uses (&PATTERN (insn), local_cprop_find_used_regs, NULL);
 	      if (note)
-		find_used_regs (&XEXP (note, 0), NULL);
+		local_cprop_find_used_regs (&XEXP (note, 0), NULL);
 
 	      for (reg_used = &reg_use_table[0]; reg_use_count > 0;
 		   reg_used++, reg_use_count--)