(significant_bits, num_sign_bit_copies): Handle SUBREGs made for promoted

variables.

From-SVN: r2215

diff --git a/gcc/combine.c b/gcc/combine.c
index 05c7c94aa1d0669ec805a230b55bd39a741e0346..044286000ad11005e176547cd246c1c2fc6ebb69 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6083,6 +6083,14 @@ significant_bits (x, mode)
       break;
 
     case SUBREG:
+      /* If this is a SUBREG formed for a promoted variable that has
+        been zero-extended, we know that at least the high-order bits
+        are zero, though others might be too.  */
+
+      if (SUBREG_PROMOTED_VAR_P (x) && SUBREG_PROMOTED_UNSIGNED_P (x))
+       significant = (GET_MODE_MASK (GET_MODE (x))
+                      & significant_bits (SUBREG_REG (x), GET_MODE (x)));
+
       /* If the inner mode is a single word for both the host and target
         machines, we can compute this from which bits of the inner
         object are known significant.  */
@@ -6220,6 +6228,14 @@ num_sign_bit_copies (x, mode)
       return (sig == 0 ? bitwidth : bitwidth - floor_log2 (sig) - 1);
 
     case SUBREG:
+      /* If this is a SUBREG for a promoted object that is sign-extended
+        and we are looking at it in a wider mode, we know that at least the
+        high-order bits are known to be sign bit copies.  */
+
+      if (SUBREG_PROMOTED_VAR_P (x) && ! SUBREG_PROMOTED_UNSIGNED_P (x))
+       return (GET_MODE_BITSIZE (mode) - GET_MODE_BITSIZE (GET_MODE (x))
+               + num_sign_bit_copies (SUBREG_REG (x), GET_MODE (x)));
+
       /* For a smaller object, just ignore the high bits. */
       if (bitwidth <= GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))))
        {