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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-11-23 13:54:17 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-11-23 13:54:17 +0000 |
| commit | f238f50aaf8a68f16dcc43a017aa32cbb73e938e (patch) | |
| tree | f2f2a0dd61a14d7ee11ff864268fbc0fc96406c0 /docs/HistoricalNotes | |
| parent | e4513b1fc5eb44885a3a21e83664289e30542cdf (diff) | |
| download | external_llvm-f238f50aaf8a68f16dcc43a017aa32cbb73e938e.zip external_llvm-f238f50aaf8a68f16dcc43a017aa32cbb73e938e.tar.gz external_llvm-f238f50aaf8a68f16dcc43a017aa32cbb73e938e.tar.bz2 | |
X86: Use btq for bit tests if the immediate can't be encoded in 32 bits.
Before:
movabsq $4294967296, %rax ## encoding: [0x48,0xb8,0x00,0x00,0x00,0x00,0x01,0x00,0x00,0x00]
testq %rax, %rdi ## encoding: [0x48,0x85,0xf8]
jne LBB0_2 ## encoding: [0x75,A]
After:
btq $32, %rdi ## encoding: [0x48,0x0f,0xba,0xe7,0x20]
jb LBB0_2 ## encoding: [0x72,A]
btq is usually slower than testq because it doesn't fuse with the jump, but here we're better off
saving one register and a giant movabsq.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145103 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/HistoricalNotes')
0 files changed, 0 insertions, 0 deletions