Changeset 203488 in webkit for trunk/Source/JavaScriptCore/b3/B3ValueRep.cpp

Timestamp:

Jul 20, 2016, 10:24:54 PM (9 years ago)

Author:

[email protected]

Message:

FTL snippet generators should be able to request a different register for output and input
​https://bugs.webkit.org/show_bug.cgi?id=160010
rdar://problem/27439330

Reviewed by Saam Barati.

The BitOr and BitXor snippet generators have problems if the register for the right input is
the same as the register for the result. We could fix those generators, but I'm not convinced
that the other snippet generators don't have this bug. So, the approach that this patch takes
is to teach the FTL to request that B3 to use a different register for the result than for
any input to the snippet patchpoint.

Air already has the ability to let any instruction do an EarlyDef, which means exactly this.
But B3 did not expose this via ValueRep. This patch exposes this in ValueRep as
SomeEarlyRegister. That's most of the change.

This adds a testb3 test for SomeEarlyRegister and a regression test for this particular
problem. The regression test failed on trunk JSC before this.

• b3/B3LowerToAir.cpp:

(JSC::B3::Air::LowerToAir::lower):

• b3/B3PatchpointSpecial.cpp:

(JSC::B3::PatchpointSpecial::forEachArg):
(JSC::B3::PatchpointSpecial::admitsStack):

• b3/B3StackmapSpecial.cpp:

(JSC::B3::StackmapSpecial::forEachArgImpl):
(JSC::B3::StackmapSpecial::isArgValidForRep):

• b3/B3Validate.cpp:
• b3/B3ValueRep.cpp:

(JSC::B3::ValueRep::addUsedRegistersTo):
(JSC::B3::ValueRep::dump):
(WTF::printInternal):

• b3/B3ValueRep.h:

(JSC::B3::ValueRep::ValueRep):
(JSC::B3::ValueRep::reg):
(JSC::B3::ValueRep::isAny):
(JSC::B3::ValueRep::isReg):
(JSC::B3::ValueRep::isSomeRegister): Deleted.

• b3/testb3.cpp:
• ftl/FTLLowerDFGToB3.cpp:

(JSC::FTL::DFG::LowerDFGToB3::emitBinarySnippet):
(JSC::FTL::DFG::LowerDFGToB3::emitBinaryBitOpSnippet):
(JSC::FTL::DFG::LowerDFGToB3::emitRightShiftSnippet):

• tests/stress/ftl-bit-xor-right-result-interference.js: Added.

File:

• trunk/Source/JavaScriptCore/b3/B3ValueRep.cpp (modified) (3 diffs)

trunk/Source/JavaScriptCore/b3/B3ValueRep.cpp

@@ -41 +41 @@
     case LateColdAny:
     case SomeRegister:
+    case SomeEarlyRegister:
     case Constant:
         return;
@@ -71 +72 @@
     case LateColdAny:
     case SomeRegister:
+    case SomeEarlyRegister:
         return;
     case LateRegister:
@@ -174 +176 @@
         out.print("SomeRegister");
         return;
+    case ValueRep::SomeEarlyRegister:
+        out.print("SomeEarlyRegister");
+        return;
     case ValueRep::Register:
         out.print("Register");