diff options
Diffstat (limited to 'gcc/combine.c')
| -rw-r--r-- | gcc/combine.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index de3afcc..7eaaf47 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -9674,6 +9674,31 @@ reg_num_sign_bit_copies_for_combine (const_rtx x, enum machine_mode mode, 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 |