JIT/AArch64: Use 'tbnz/tbz' to check the signedness #7123
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'tbnz/tbz' instruction can be used to check whether a given W or X
register value is negative or positive.
For example,
```
tst x0, x0
blt >1
```
can be optimized as `tbnz x0, php#63, >1`
It's important to note that the jump range of 'tbnz/tbz' is limited, and
it's better NOT to use 'tbnz/tbz' if the target of 'b.cond' is a label
in section .cold_code or a global label, such as the instruction
sequence `tst RETVALw, RETVALw; blt ->trace_halt` at function
zend_jit_trace_exit_stub(), and the instruction sequence `tst REG0,
REG0; blt >7` at function zend_jit_incdec_obj().
Minor updates:
Use macros BW_OP_32_WITH_CONST and GC_ADDREF at function
zend_jit_push_call_frame().
Change-Id: I1597609bdabf55ea2f9d24528e7a037bc3e5c3a1
dstogov
approved these changes
Jun 9, 2021
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'tbnz/tbz' instruction can be used to check whether a given W or X
register value is negative or positive.
For example,
tst x0, x0; blt >1can be optimized as
tbnz x0, #63, >1It's important to note that the jump range of 'tbnz/tbz' is limited, and
it's better NOT to use 'tbnz/tbz' if the target of 'b.cond' is a label
in section .cold_code or a global label, such as the instruction
sequence
tst RETVALw, RETVALw; blt ->trace_haltat functionzend_jit_trace_exit_stub(), and the instruction sequence
tst REG0, REG0; blt >7at function zend_jit_incdec_obj().Minor updates:
Use macros BW_OP_32_WITH_CONST and GC_ADDREF at function
zend_jit_push_call_frame().
Test: all ~4k .phpt test cases under
tests/ Zend/tests/ ext/opcache/tests/jit/can pass for Linux JIT/arm64.Note that in total 8 JIT variants are tested, covering ZTS/nonZTS, HYBRID/VM, and functional/tracing JIT.
Change-Id: I1597609bdabf55ea2f9d24528e7a037bc3e5c3a1