diff options
| author | Richard Kenner <kenner@gcc.gnu.org> | 1993-08-08 17:31:39 -0400 |
|---|---|---|
| committer | Richard Kenner <kenner@gcc.gnu.org> | 1993-08-08 17:31:39 -0400 |
| commit | 312def2eda47dd591c50f9bf9959fc3129e275e0 (patch) | |
| tree | 183cc19aba5df130a788a5bd88d0675d808837a5 | |
| parent | 00aae7b152f77c0aa1e0bd9ac2001635ca9c7c95 (diff) | |
| download | gcc-312def2eda47dd591c50f9bf9959fc3129e275e0.zip gcc-312def2eda47dd591c50f9bf9959fc3129e275e0.tar.gz gcc-312def2eda47dd591c50f9bf9959fc3129e275e0.tar.bz2 | |
(num_sign_bit_copies): Properly handle case when MODE is narrower than that of X.
(num_sign_bit_copies): Properly handle case when MODE is narrower than that
of X.
(simplify_shift_const): Remove change of July 26.
From-SVN: r5110
| -rw-r--r-- | gcc/combine.c | 43 |
1 files changed, 21 insertions, 22 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index 1362dbc..ffc92f8 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -6687,6 +6687,11 @@ num_sign_bit_copies (x, mode) bitwidth = GET_MODE_BITSIZE (mode); + /* For a smaller object, just ignore the high bits. */ + if (bitwidth < GET_MODE_BITSIZE (GET_MODE (x))) + return MAX (1, (num_sign_bit_copies (x, GET_MODE (x)) + - (GET_MODE_BITSIZE (GET_MODE (x)) - bitwidth))); + switch (code) { case REG: @@ -7181,31 +7186,25 @@ simplify_shift_const (x, code, result_mode, varop, count) else if (count < 0) abort (); - /* If we have replaced VAROP with something wider - (such as, the SUBREG_REG), then this won't work; - num_sign_bit_copies will give the wrong answer in that case. */ - if (shift_mode == GET_MODE (varop)) + /* An arithmetic right shift of a quantity known to be -1 or 0 + is a no-op. */ + if (code == ASHIFTRT + && (num_sign_bit_copies (varop, shift_mode) + == GET_MODE_BITSIZE (shift_mode))) { - /* An arithmetic right shift of a quantity known to be -1 or 0 - is a no-op. */ - if (code == ASHIFTRT - && (num_sign_bit_copies (varop, shift_mode) - == GET_MODE_BITSIZE (shift_mode))) - { - count = 0; - break; - } + count = 0; + break; + } - /* If we are doing an arithmetic right shift and discarding all but - the sign bit copies, this is equivalent to doing a shift by the - bitsize minus one. Convert it into that shift because it will often - allow other simplifications. */ + /* If we are doing an arithmetic right shift and discarding all but + the sign bit copies, this is equivalent to doing a shift by the + bitsize minus one. Convert it into that shift because it will often + allow other simplifications. */ - if (code == ASHIFTRT - && (count + num_sign_bit_copies (varop, shift_mode) - >= GET_MODE_BITSIZE (shift_mode))) - count = GET_MODE_BITSIZE (shift_mode) - 1; - } + if (code == ASHIFTRT + && (count + num_sign_bit_copies (varop, shift_mode) + >= GET_MODE_BITSIZE (shift_mode))) + count = GET_MODE_BITSIZE (shift_mode) - 1; /* We simplify the tests below and elsewhere by converting ASHIFTRT to LSHIFTRT if we know the sign bit is clear. |