Air should expose API for pinning registers
https://bugs.webkit.org/show_bug.cgi?id=163175
Reviewed by Keith Miller.
You can now call Procedure::pinRegister(), or Code::pinRegister(), and it will make this
register behave as follows:
- B3 and Air will emit no code that modifies the value in this register, except if that
happens via a Patchpoint or stackmap constraint (i.e. the user explicitly asked for it).
- B3 and Air will allow others to modify the register. For example, if the register is not
callee-save, then the compiler knows that the register's value will be trashed by any
C-style call.
- Air will be happy to emit code that reads from this register, including coalescing tmps
with it, so longer as there is no interference (i.e. no chance of the register's value
changing). For example, if we went back to having pinned tag registers, we would tell B3
to use them by (1) excluding them from any clobber set (easy, since they're callee save)
and (2) emitting ArgumentReg to grab their value. There's a test that does this.
This is accomplished by taking regsInPriorityOrder() and making it a method of Code. Air
already used this API when choosing registers in register allocation. Code now also vends a
mutableRegs() set, which is derived from regsInPriorityOrder(), that can quickly tell you if
a register can be mutated. Doing it this way means that most of this is a purely mechanical
change. The calls to mutableRegs() are the places where we had to change logic:
- The register allocators needs to know that coalescing with a precolored pinned tmp is free.
- The callee-save handler needs to know that we're not supposed to save/restore pinned
registers.
Note that in this scheme, pinned registers are simply registers that do not appear in
regsInPriorityOrder(). This means, for example, that we will now say that FP is pinned. So,
this means that you can also pin registers by calling setRegsInPriorityOrder() and passing a
vector that excludes some registers. More generally, this means that clients can now tweak
the register allocator's register preferences, since the ordering in that list reflects the
order in which the allocator will try registers.
* CMakeLists.txt:
* JavaScriptCore.xcodeproj/project.pbxproj:
* b3/B3Procedure.cpp:
(JSC::B3::Procedure::pinRegister):
* b3/B3Procedure.h:
* b3/air/AirCode.cpp:
(JSC::B3::Air::Code::Code):
(JSC::B3::Air::Code::setRegsInPriorityOrder):
(JSC::B3::Air::Code::pinRegister):
* b3/air/AirCode.h:
(JSC::B3::Air::Code::regsInPriorityOrder):
(JSC::B3::Air::Code::mutableRegs):
(JSC::B3::Air::Code::isPinned):
(JSC::B3::Air::Code::regsInPriorityOrderImpl):
(JSC::B3::Air::Code::proc): Deleted.
* b3/air/AirEmitShuffle.cpp:
(JSC::B3::Air::emitShuffle):
* b3/air/AirEmitShuffle.h:
* b3/air/AirHandleCalleeSaves.cpp:
(JSC::B3::Air::handleCalleeSaves):
* b3/air/AirIteratedRegisterCoalescing.cpp:
* b3/air/AirLowerAfterRegAlloc.cpp:
(JSC::B3::Air::lowerAfterRegAlloc):
* b3/air/AirRegisterPriority.cpp: Removed.
* b3/air/AirRegisterPriority.h: Removed.
* b3/air/AirSpillEverything.cpp:
(JSC::B3::Air::spillEverything):
* b3/air/testair.cpp:
(JSC::B3::Air::testShuffleBroadcastAllRegs):
(JSC::B3::Air::testShuffleShiftAllRegs):
(JSC::B3::Air::testShuffleRotateAllRegs):
(JSC::B3::Air::testShuffleShiftMemoryAllRegs):
(JSC::B3::Air::testShuffleShiftMemoryAllRegs64):
(JSC::B3::Air::testShuffleShiftMemoryAllRegsMixedWidth):
(JSC::B3::Air::testShuffleRotateMemoryAllRegs64):
(JSC::B3::Air::testShuffleRotateMemoryAllRegsMixedWidth):
* b3/testb3.cpp:
(JSC::B3::testPinRegisters):
(JSC::B3::run):
* jit/RegisterSet.h:
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@207004 268f45cc-cd09-0410-ab3c-d52691b4dbfc
18 files changed
