Bug 89752

Summary:

DFG tier-up should happen in prologues, not epilogues

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED FIXED

Severity:

Normal

Priority:

Version:

528+ (Nightly build)

Hardware:

All

OS:

All

Attachments:

Description	Flags
the patch	webkit-ews: commit-queue-
the patch	ggaren: review+

Filip Pizlo

Reported 2012-06-22 02:22:58 PDT

This change has two outcomes: 1) Slightly reduces the likelihood that a function will be optimized both standalone and via inlining. Previously, if you had a call sequence like foo() calls bar() exactly once, and nobody else calls bar(), then bar() would get optimized first (because it returns first) and then foo() gets optimized. If foo() can inline bar() then that means that bar() gets optimized twice. But now, if we optimize in prologues, then foo() will be optimized first. If it inlines bar(), that means that there will no longer be any calls to bar(). 2) It lets us kill some code in JITStubs. Epilogue tier-up was very different from loop tier-up, since epilogue tier-up should not attempt OSR. But prologue tier-up requires OSR (albeit really easy OSR since it's the top of the compilation unit), so it becomes just like loop tier-up. As a result, we now have one optimizatio hook (cti_optimize) instead of two (cti_optimize_from_loop and cti_optimize_from_ret).

Attachments
the patch (21.71 KB, patch) 2012-06-22 02:29 PDT, Filip Pizlo	webkit-ews: commit-queue-	Details Formatted Diff Diff
the patch (23.29 KB, patch) 2012-06-22 15:10 PDT, Filip Pizlo	ggaren: review+	Details Formatted Diff Diff
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