Get the right COST for a SUBREG when truncating

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@13549 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/cse.c b/gcc/cse.c
index e6c7e9f..cc9c142 100644 (file)
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -1,5 +1,5 @@
 /* Common subexpression elimination for GNU compiler.
-   Copyright (C) 1987, 88, 89, 92-5, 1996 Free Software Foundation, Inc.
+   Copyright (C) 1987, 88, 89, 92-6, 1997 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -478,12 +478,24 @@ struct table_elt
   ((REG_USERVAR_P (N) && REGNO (N) < FIRST_PSEUDO_REGISTER)    \
    || CHEAP_REGNO (REGNO (N)))
 
-#define COST(X)                                                \
-  (GET_CODE (X) == REG                                 \
-   ? (CHEAP_REG (X) ? 0                                        \
-      : REGNO (X) >= FIRST_PSEUDO_REGISTER ? 1         \
-      : 2)                                             \
-   : rtx_cost (X, SET) * 2)
+#define COST(X)                                                                \
+  (GET_CODE (X) == REG                                                 \
+   ? (CHEAP_REG (X) ? 0                                                        \
+      : REGNO (X) >= FIRST_PSEUDO_REGISTER ? 1                         \
+      : 2)                                                             \
+   : ((GET_CODE (X) == SUBREG                                          \
+       && GET_CODE (SUBREG_REG (X)) == REG                             \
+       && GET_MODE_CLASS (GET_MODE (X)) == MODE_INT                    \
+       && GET_MODE_CLASS (GET_MODE (SUBREG_REG (X))) == MODE_INT       \
+       && (GET_MODE_SIZE (GET_MODE (X))                                        \
+          < GET_MODE_SIZE (GET_MODE (SUBREG_REG (X))))                 \
+       && subreg_lowpart_p (X)                                         \
+       && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (GET_MODE (X)),      \
+                                GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (X))))) \
+      ? (CHEAP_REG (SUBREG_REG (X)) ? 0                                        \
+        : REGNO (SUBREG_REG (X)) >= FIRST_PSEUDO_REGISTER ? 1          \
+        : 2)                                                           \
+      : rtx_cost (X, SET) * 2))
 
 /* Determine if the quantity number for register X represents a valid index
    into the `qty_...' variables.  */