Changeset 165196 in webkit for trunk/Source/JavaScriptCore/ftl/FTLSlowPathCall.cpp

Timestamp:

Mar 6, 2014, 10:33:18 AM (11 years ago)

Author:

[email protected]

Message:

Clarify how we deal with "special" registers
​https://bugs.webkit.org/show_bug.cgi?id=129806

Reviewed by Michael Saboff.

Previously we had two different places that defined what "stack" registers are, a thing
called "specialRegisters" that had unclear meaning, and a really weird "firstRealRegister"/
"secondRealRegister"/"nextRegister" idiom in MacroAssembler that appeared to only be used by
one place and had a baked-in notion of what it meant for a register to be "real" or not.

It's not cool to use words like "real" and "special" to describe registers, especially if you
fail to qualify what that means. This originally made sense on X86 - "real" registers were
the ones that weren't "stack related" (so "real" was the opposite of "stack"). But on ARM64,
you also have to worry about the LR register, which we'd want to say is "not real" but it's
also not a "stack" register. This got super confusing.

So, this patch removes any mention of "real" registers, consolidates the knowledge of what is
a "stack" register, and uses the word special only in places where it's clearly defined and
where no better word comes to mind.

This cleans up the code and fixes what seems like it was probably a harmless ARM64 bug: the
Reg and RegisterSet data structures would sometimes think that FP was Q0. Somehow this
magically didn't break anything because you never need to save/restore either FP or Q0, but
it was still super weird.

• assembler/ARM64Assembler.h:

(JSC::ARM64Assembler::lastRegister):

• assembler/MacroAssembler.h:

(JSC::MacroAssembler::nextRegister):

• ftl/FTLLocation.cpp:

(JSC::FTL::Location::restoreInto):

• ftl/FTLSaveRestore.cpp:

(JSC::FTL::saveAllRegisters):
(JSC::FTL::restoreAllRegisters):

• ftl/FTLSlowPathCall.cpp:
• jit/RegisterSet.cpp:

(JSC::RegisterSet::reservedHardwareRegisters):
(JSC::RegisterSet::runtimeRegisters):
(JSC::RegisterSet::specialRegisters):
(JSC::RegisterSet::calleeSaveRegisters):

• jit/RegisterSet.h:

File:

• trunk/Source/JavaScriptCore/ftl/FTLSlowPathCall.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ftl/FTLSlowPathCall.cpp

@@ -53 +53 @@
         , m_returnRegister(returnRegister)
     {
-        // We don't care that you're using callee-save or stack registers.
+        // We don't care that you're using callee-save, stack, or hardware registers.
         m_usedRegisters.exclude(RegisterSet::stackRegisters());
+        m_usedRegisters.exclude(RegisterSet::reservedHardwareRegisters());
         m_usedRegisters.exclude(RegisterSet::calleeSaveRegisters());