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| author | nemet <nemet@138bc75d-0d04-0410-961f-82ee72b054a4> | 2007-07-06 00:20:46 +0000 |
|---|---|---|
| committer | nemet <nemet@138bc75d-0d04-0410-961f-82ee72b054a4> | 2007-07-06 00:20:46 +0000 |
| commit | c07054e9cb2002971dbefcf713d5dd3ee131bfc4 (patch) | |
| tree | f707059f7c1e3dc69a66829d782c26a55fe2be16 /gcc/rtlanal.c | |
| parent | cfaeedae3635b0dc78d5ffc3b0df8a6f91a1231e (diff) | |
| download | gcc-c07054e9cb2002971dbefcf713d5dd3ee131bfc4.tar.gz | |
* rtlanal.c (num_sign_bit_copies1): Improve cases of ANDing or
IORing with a constant.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@126397 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/rtlanal.c')
| -rw-r--r-- | gcc/rtlanal.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index 3cdb76a16bd..9535104e707 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -4290,6 +4290,25 @@ num_sign_bit_copies1 (rtx x, enum machine_mode mode, rtx known_x, known_x, known_mode, known_ret); num1 = cached_num_sign_bit_copies (XEXP (x, 1), mode, known_x, known_mode, known_ret); + + /* If num1 is clearing some of the top bits then regardless of + the other term, we are guaranteed to have at least that many + high-order zero bits. */ + if (code == AND + && num1 > 1 + && bitwidth <= HOST_BITS_PER_WIDE_INT + && GET_CODE (XEXP (x, 1)) == CONST_INT + && !(INTVAL (XEXP (x, 1)) & ((HOST_WIDE_INT) 1 << (bitwidth - 1)))) + return num1; + + /* Similarly for IOR when setting high-order bits. */ + if (code == IOR + && num1 > 1 + && bitwidth <= HOST_BITS_PER_WIDE_INT + && GET_CODE (XEXP (x, 1)) == CONST_INT + && (INTVAL (XEXP (x, 1)) & ((HOST_WIDE_INT) 1 << (bitwidth - 1)))) + return num1; + return MIN (num0, num1); case PLUS: case MINUS: |