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| author | Adam Nemet <anemet@caviumnetworks.com> | 2007-07-06 00:20:46 +0000 |
|---|---|---|
| committer | Adam Nemet <nemet@gcc.gnu.org> | 2007-07-06 00:20:46 +0000 |
| commit | 22761ec3b9b4688e515019b6b97025fda5be6a44 (patch) | |
| tree | f707059f7c1e3dc69a66829d782c26a55fe2be16 /gcc/rtlanal.c | |
| parent | 4f0a96f532a86eb4b81e932af2208a81ba169b33 (diff) | |
| download | gcc-22761ec3b9b4688e515019b6b97025fda5be6a44.zip gcc-22761ec3b9b4688e515019b6b97025fda5be6a44.tar.gz gcc-22761ec3b9b4688e515019b6b97025fda5be6a44.tar.bz2 | |
rtlanal.c (num_sign_bit_copies1): Improve cases of ANDing or IORing with a constant.
* rtlanal.c (num_sign_bit_copies1): Improve cases of ANDing or
IORing with a constant.
From-SVN: r126397
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 3cdb76a..9535104 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: |