* combine.c (apply_distributive_law <SUBREG>): Check

	TRULY_NOOP_TRUNCATION.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@109261 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index cac2479..1be3f95 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2006-01-02  Adam Nemet  <anemet@caviumnetworks.com>
+
+       * combine.c (apply_distributive_law <SUBREG>): Check
+       TRULY_NOOP_TRUNCATION.
+
 2006-01-02  Geoffrey Keating  <geoffk@apple.com>
 
        * dwarf2out.c (have_switched_text_section): Delete.

diff --git a/gcc/combine.c b/gcc/combine.c
index 1361b10..e9bd667 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7798,7 +7798,12 @@ apply_distributive_law (rtx x)
          || (GET_MODE_SIZE (GET_MODE (lhs))
              > GET_MODE_SIZE (GET_MODE (SUBREG_REG (lhs))))
          || VECTOR_MODE_P (GET_MODE (lhs))
-         || GET_MODE_SIZE (GET_MODE (SUBREG_REG (lhs))) > UNITS_PER_WORD)
+         || GET_MODE_SIZE (GET_MODE (SUBREG_REG (lhs))) > UNITS_PER_WORD
+         /* Result might need to be truncated.  Don't change mode if
+            explicit truncation is needed.  */
+         || !TRULY_NOOP_TRUNCATION
+              (GET_MODE_BITSIZE (GET_MODE (x)),
+               GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (lhs)))))
        return x;
 
       tem = simplify_gen_binary (code, GET_MODE (SUBREG_REG (lhs)),