(nonzero_bits): Ifdef out calls to num_sign_bit_copies.

Add dummy define/undef for num_sign_bit_copies.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@13314 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/combine.c b/gcc/combine.c
index f4e0b97..57100b9 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7072,6 +7072,13 @@ simplify_and_const_int (x, mode, varop, constop)
   return x;
 }
 \f
+/* We let num_sign_bit_copies recur into nonzero_bits as that is useful.
+   We don't let nonzero_bits recur into num_sign_bit_copies, because that
+   is less useful.  We can't allow both, because that results in exponential
+   run time recusion.  There is a nullstone testcase that triggered
+   this.  This macro avoids accidental uses of num_sign_bit_copies.  */
+#define num_sign_bit_copies()
+
 /* Given an expression, X, compute which bits in X can be non-zero.
    We don't care about bits outside of those defined in MODE.
 
@@ -7246,18 +7253,26 @@ nonzero_bits (x, mode)
       break;
 
     case NEG:
+#if 0
+      /* Disabled to avoid exponential mutual recursion between nonzero_bits
+        and num_sign_bit_copies.  */
       if (num_sign_bit_copies (XEXP (x, 0), GET_MODE (x))
          == GET_MODE_BITSIZE (GET_MODE (x)))
        nonzero = 1;
+#endif
 
       if (GET_MODE_SIZE (GET_MODE (x)) < mode_width)
        nonzero |= (GET_MODE_MASK (mode) & ~ GET_MODE_MASK (GET_MODE (x)));
       break;
 
     case ABS:
+#if 0
+      /* Disabled to avoid exponential mutual recursion between nonzero_bits
+        and num_sign_bit_copies.  */
       if (num_sign_bit_copies (XEXP (x, 0), GET_MODE (x))
          == GET_MODE_BITSIZE (GET_MODE (x)))
        nonzero = 1;
+#endif
       break;
 
     case TRUNCATE:
@@ -7456,6 +7471,9 @@ nonzero_bits (x, mode)
 
   return nonzero;
 }
+
+/* See the macro definition above.  */
+#undef num_sign_bit_copies
 \f
 /* Return the number of bits at the high-order end of X that are known to
    be equal to the sign bit.  X will be used in mode MODE; if MODE is