Bug 171079

Summary: virtualThunkFor() needs to materialize its of tagMaskRegister for tail calls.
Product: WebKit Reporter: Mark Lam <mark.lam>
Component: JavaScriptCoreAssignee: Mark Lam <mark.lam>
Status: RESOLVED FIXED    
Severity: Normal CC: fpizlo, jfbastien, keith_miller, msaboff, saam, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
proposed patch.
saam: review+
patch for landing. none

Mark Lam
Reported 2017-04-20 15:05:31 PDT
This is because tail calls would restore callee saved registers (and therefore, potentially clobber the tag registers) before jumping to the thunk. <rdar://problem/31684756>
Attachments
proposed patch. (4.30 KB, patch)
2017-04-20 15:52 PDT, Mark Lam 		saam: review+
DetailsFormatted DiffDiff
patch for landing. (3.61 KB, patch)
2017-04-20 16:32 PDT, Mark Lam 		no flags
DetailsFormatted DiffDiff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.
Mark Lam
Comment 1 2017-04-20 15:52:03 PDT
Created attachment 307654 [details] proposed patch.
Saam Barati
Comment 2 2017-04-20 16:01:02 PDT
Comment on attachment 307654 [details] proposed patch. View in context: https://bugs.webkit.org/attachment.cgi?id=307654&action=review r=me > Source/JavaScriptCore/jit/AssemblyHelpers.h:429 > + void emitMaterializeTagMaskInRegister(GPRReg reg) > + { > + move(MacroAssembler::TrustedImm64(TagTypeNumber), reg); > + orPtr(MacroAssembler::TrustedImm32(TagBitTypeOther), reg, reg); > + } Please verify this is less code on X86_64 and ARM64, otherwise, please specialize to those platforms what you do such that we emit less code.
Mark Lam
Comment 3 2017-04-20 16:07:48 PDT
(In reply to Saam Barati from comment #2) > Comment on attachment 307654 [details] > proposed patch. > > View in context: > https://bugs.webkit.org/attachment.cgi?id=307654&action=review > > r=me > > > Source/JavaScriptCore/jit/AssemblyHelpers.h:429 > > + void emitMaterializeTagMaskInRegister(GPRReg reg) > > + { > > + move(MacroAssembler::TrustedImm64(TagTypeNumber), reg); > > + orPtr(MacroAssembler::TrustedImm32(TagBitTypeOther), reg, reg); > > + } > > Please verify this is less code on X86_64 and ARM64, otherwise, please > specialize to those platforms what you do such that we emit less code. I think it's better to use a single instruction. I'll switch to doing that.
Mark Lam
Comment 4 2017-04-20 16:32:40 PDT
Created attachment 307658 [details] patch for landing.
Mark Lam
Comment 5 2017-04-20 17:31:43 PDT
Thanks for the review. Landed in r215596: <http://trac.webkit.org/r215596>.
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