* combine.c (make_extraction): Reapply to the argument of an ASHIFT.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@54846 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 15 insertions, 0 deletions

diff --git a/gcc/combine.c b/gcc/combine.c
index 3b298827413..ea12b130922 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -5968,6 +5968,21 @@ make_extraction (mode, inner, pos, pos_rtx, len,
 	is_mode = GET_MODE (SUBREG_REG (inner));
       inner = SUBREG_REG (inner);
     }
+  else if (GET_CODE (inner) == ASHIFT
+	   && GET_CODE (XEXP (inner, 1)) == CONST_INT
+	   && pos_rtx == 0 && pos == 0
+	   && len > INTVAL (XEXP (inner, 1)))
+    {
+      /* We're extracting the least significant bits of an rtx
+	 (ashift X (const_int C)), where LEN > C.  Extract the
+	 least significant (LEN - C) bits of X, giving an rtx
+	 whose mode is MODE, then shift it left C times.  */
+      new = make_extraction (mode, XEXP (inner, 0),
+			     0, 0, len - INTVAL (XEXP (inner, 1)),
+			     unsignedp, in_dest, in_compare);
+      if (new != 0)
+	return gen_rtx_ASHIFT (mode, new, XEXP (inner, 1));
+    }
 
   inner_mode = GET_MODE (inner);