Index: combine.c
===================================================================
--- combine.c (revision 186039)
+++ combine.c (working copy)
@@ -9674,6 +9674,31 @@
return NULL;
}
+/* Return the number of "extended" bits there are in X, when interpreted
+ as a quantity in MODE whose signedness is indicated by UNSIGNEDP. For
+ unsigned quantities, this is the number of high-order zero bits.
+ For signed quantities, this is the number of copies of the sign bit
+ minus 1. In both case, this function returns the number of "spare"
+ bits. For example, if two quantities for which this function returns
+ at least 1 are added, the addition is known not to overflow.
+
+ This function will always return 0 unless called during combine, which
+ implies that it must be called from a define_split. */
+
+unsigned int
+extended_count (const_rtx x, enum machine_mode mode, int unsignedp)
+{
+ if (nonzero_sign_valid == 0)
+ return 0;
+
+ return (unsignedp
+ ? (HWI_COMPUTABLE_MODE_P (mode)
+ ? (unsigned int) (GET_MODE_PRECISION (mode) - 1
+ - floor_log2 (nonzero_bits (x, mode)))
+ : 0)
+ : num_sign_bit_copies (x, mode) - 1);
+}
+
/* This function is called from `simplify_shift_const' to merge two
outer operations. Specifically, we have already found that we need
to perform operation *POP0 with constant *PCONST0 at the outermost
Index: rtl.h
===================================================================
--- rtl.h (revision 186039)
+++ rtl.h (working copy)
@@ -2455,6 +2455,7 @@
const_rtx, unsigned int);
/* In combine.c */
+extern unsigned int extended_count (const_rtx, enum machine_mode, int);
extern rtx remove_death (unsigned int, rtx);
extern void dump_combine_stats (FILE *);
extern void dump_combine_total_stats (FILE *);