| commit | 8918e1db432c884ebab491f9a96226acfe68fb8c | |
| author | Steve Walk <steve.walk@cavium.com> | |
| Wed, 24 May 2017 00:14:08 +0000 (23 17:14 -0700) | ||
| committer | Hhvm Bot <hhvm-bot@users.noreply.github.com> | |
| Wed, 24 May 2017 00:23:45 +0000 (23 17:23 -0700) | ||
| tree | f89bbbf2515c240aa86ac8001bb8a95ddec7fbd0 | treesnapshot (tar.gz zip) |
| parent | 3880b958237d0eaa259c6b6da3c7db6b33d0babf | commitdiff |
Aarch64 peephole using csinc
Summary:
This change introduces an Aarch64 specific pseudo instruction which
is a variation of the conditional move. One pattern seen in the OOPSLA'14
benchmark tests involved the expression like this in C
(cond) ? exp : 1;
The hard-coded zero register can be used with the csinc instruction to
create the 1.
Before
======
0x146010d0 39c0e361 ldrsb w1, [x27, #56]
0x146010d4 72001c3f tst w1, #0xff
0x146010d8 52800022 movz w2, #0x1 //<<---
0x146010dc 1a810041 csel w1, w2, w1, eq
After
=====
0x362011d0 38e16b61 ldrsb w1, [x27, x1]
0x362011d4 72001c3f tst w1, #0xff
0x362011d8 1a9f1421 csinc w1, w1, wzr, ne
This saves 1 instruction per instance.
The standard regression suite was run with 6 option sets. No new regressions
were introduced.
Closes https://github.com/facebook/hhvm/pull/7823
Differential Revision: D5112346
Pulled By: mxw
fbshipit-source-id: 44cebfb34868523c1bda9615cd4605beb34f06ed
Summary:
This change introduces an Aarch64 specific pseudo instruction which
is a variation of the conditional move. One pattern seen in the OOPSLA'14
benchmark tests involved the expression like this in C
(cond) ? exp : 1;
The hard-coded zero register can be used with the csinc instruction to
create the 1.
Before
======
0x146010d0 39c0e361 ldrsb w1, [x27, #56]
0x146010d4 72001c3f tst w1, #0xff
0x146010d8 52800022 movz w2, #0x1 //<<---
0x146010dc 1a810041 csel w1, w2, w1, eq
After
=====
0x362011d0 38e16b61 ldrsb w1, [x27, x1]
0x362011d4 72001c3f tst w1, #0xff
0x362011d8 1a9f1421 csinc w1, w1, wzr, ne
This saves 1 instruction per instance.
The standard regression suite was run with 6 option sets. No new regressions
were introduced.
Closes https://github.com/facebook/hhvm/pull/7823
Differential Revision: D5112346
Pulled By: mxw
fbshipit-source-id: 44cebfb34868523c1bda9615cd4605beb34f06ed