Handle CLOBBER in reg_overlap_mentioned_p (PR86882)

Combine will put CLOBBER (with a non-void mode) anywhere in a pattern
to poison it.  reg_overlap_mentioned_p did not handle this.  This patch
fixes that.

	PR rtl-optimization/86882
	* rtlanal.c (reg_overlap_mentioned_p): Handle CLOBBER.

From-SVN: r264400

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a0e9093ff323a012c1548477618df03b9e0f3383..6f4e131384eeda85d075b1bda2381ec2a355bd36 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-18  Segher Boessenkool  <segher@kernel.crashing.org>
+
+       PR rtl-optimization/86882
+       * rtlanal.c (reg_overlap_mentioned_p): Handle CLOBBER.
+
 2018-09-18  Uros Bizjak  <ubizjak@gmail.com>
 
        * config/i386/i386.md (*<code>extend<mode>xf2): Macroize insn from

diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index 6c620a4a3e50017a72ebab51710f32727500941d..366df7c9b3fa23a9750941884cc1116498b8399c 100644 (file)
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -1815,6 +1815,7 @@ reg_overlap_mentioned_p (const_rtx x, const_rtx in)
  recurse:
   switch (GET_CODE (x))
     {
+    case CLOBBER:
     case STRICT_LOW_PART:
     case ZERO_EXTRACT:
     case SIGN_EXTRACT:
@@ -4757,17 +4758,17 @@ nonzero_bits1 (const_rtx x, scalar_int_mode mode, const_rtx known_x,
          nonzero &= cached_nonzero_bits (SUBREG_REG (x), mode,
                                          known_x, known_mode, known_ret);
 
-          /* On many CISC machines, accessing an object in a wider mode
+         /* On many CISC machines, accessing an object in a wider mode
             causes the high-order bits to become undefined.  So they are
             not known to be zero.  */
          rtx_code extend_op;
          if ((!WORD_REGISTER_OPERATIONS
               /* If this is a typical RISC machine, we only have to worry
                  about the way loads are extended.  */
+              || !MEM_P (SUBREG_REG (x))
               || ((extend_op = load_extend_op (inner_mode)) == SIGN_EXTEND
                   ? val_signbit_known_set_p (inner_mode, nonzero)
-                  : extend_op != ZERO_EXTEND)
-              || (!MEM_P (SUBREG_REG (x)) && !REG_P (SUBREG_REG (x))))
+                  : extend_op != ZERO_EXTEND))
              && xmode_width > inner_width)
            nonzero
              |= (GET_MODE_MASK (GET_MODE (x)) & ~GET_MODE_MASK (inner_mode));