Fix for PR 3783.

	* alias.c (clear_reg_alias_info): New.
	* flow.c (attempt_auto_inc): Call clear_reg_alias_info.
	* rtl.h (clear_reg_alias_info): Declare.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@45482 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 14 insertions, 0 deletions

diff --git a/gcc/alias.c b/gcc/alias.c
index d8e9d42e3b3..8c6ad5f0eb3 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -960,6 +960,20 @@ record_base_value (regno, val, invariant)
   reg_base_value[regno] = find_base_value (val);
 }
 
+/* Clear alias info for a register.  This is used if an RTL transformation
+   changes the value of a register.  This is used in flow by AUTO_INC_DEC
+   optimizations.  We don't need to clear reg_base_value, since flow only
+   changes the offset.  */
+
+void
+clear_reg_alias_info (rtx reg)
+{
+  int regno = REGNO (reg);
+
+  if (regno < reg_known_value_size)
+    reg_known_value[regno] = reg;
+}
+
 /* Returns a canonical version of X, from the point of view alias
    analysis.  (For example, if X is a MEM whose address is a register,
    and the register has a known value (say a SYMBOL_REF), then a MEM