cse.c (cse_insn): Calculate src_eqv for ZERO_EXTRACT.

gcc/ChangeLog:

2015-07-12  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* cse.c (cse_insn): Calculate src_eqv for ZERO_EXTRACT.
	* emit-rtl.c (set_for_reg_notes): Allow ZERO_EXTRACT to set
	REG_EQUAL note.

From-SVN: r225721

1 files changed, 42 insertions, 7 deletions

diff --git a/gcc/cse.c b/gcc/cse.c
index 255c4db..b06c669 100644
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -4524,14 +4524,49 @@ cse_insn (rtx_insn *insn)
   canonicalize_insn (insn, &sets, n_sets);
 
   /* If this insn has a REG_EQUAL note, store the equivalent value in SRC_EQV,
-     if different, or if the DEST is a STRICT_LOW_PART.  The latter condition
-     is necessary because SRC_EQV is handled specially for this case, and if
-     it isn't set, then there will be no equivalence for the destination.  */
+     if different, or if the DEST is a STRICT_LOW_PART/ZERO_EXTRACT.  The
+     latter condition is necessary because SRC_EQV is handled specially for
+     this case, and if it isn't set, then there will be no equivalence
+     for the destination.  */
   if (n_sets == 1 && REG_NOTES (insn) != 0
-      && (tem = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0
-      && (! rtx_equal_p (XEXP (tem, 0), SET_SRC (sets[0].rtl))
-	  || GET_CODE (SET_DEST (sets[0].rtl)) == STRICT_LOW_PART))
-    src_eqv = copy_rtx (XEXP (tem, 0));
+      && (tem = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0)
+    {
+      if ((! rtx_equal_p (XEXP (tem, 0), SET_SRC (sets[0].rtl)))
+	  || GET_CODE (SET_DEST (sets[0].rtl)) == STRICT_LOW_PART)
+	src_eqv = copy_rtx (XEXP (tem, 0));
+
+      /* If DEST is of the form ZERO_EXTACT, as in:
+	 (set (zero_extract:SI (reg:SI 119)
+		  (const_int 16 [0x10])
+		  (const_int 16 [0x10]))
+	      (const_int 51154 [0xc7d2]))
+	 REG_EQUAL note will specify the value of register (reg:SI 119) at this
+	 point.  Note that this is different from SRC_EQV. We can however
+	 calculate SRC_EQV with the position and width of ZERO_EXTRACT.  */
+      else if (GET_CODE (SET_DEST (sets[0].rtl)) == ZERO_EXTRACT
+	       && CONST_INT_P (src_eqv)
+	       && CONST_INT_P (XEXP (SET_DEST (sets[0].rtl), 1))
+	       && CONST_INT_P (XEXP (SET_DEST (sets[0].rtl), 2)))
+	{
+	  rtx dest_reg = XEXP (SET_DEST (sets[0].rtl), 0);
+	  rtx width = XEXP (SET_DEST (sets[0].rtl), 1);
+	  rtx pos = XEXP (SET_DEST (sets[0].rtl), 2);
+	  HOST_WIDE_INT val = INTVAL (src_eqv);
+	  HOST_WIDE_INT mask;
+	  unsigned int shift;
+	  if (BITS_BIG_ENDIAN)
+	    shift = GET_MODE_PRECISION (GET_MODE (dest_reg))
+	      - INTVAL (pos) - INTVAL (width);
+	  else
+	    shift = INTVAL (pos);
+	  if (INTVAL (width) == HOST_BITS_PER_WIDE_INT)
+	    mask = ~(HOST_WIDE_INT) 0;
+	  else
+	    mask = ((HOST_WIDE_INT) 1 << INTVAL (width)) - 1;
+	  val = (val >> shift) & mask;
+	  src_eqv = GEN_INT (val);
+	}
+    }
 
   /* Set sets[i].src_elt to the class each source belongs to.
      Detect assignments from or to volatile things