Attachment 361691 Details for Bug 194475 – Patch

[patch] Patch

bug-194475-20190211102347.patch (text/plain), 2.35 KB, created by Robin Morisset on 2019-02-11 10:23:48 PST

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Creator: Robin Morisset

Created: 2019-02-11 10:23:48 PST

Size: 2.35 KB

patch

obsolete

>Index: Source/JavaScriptCore/ChangeLog
>===================================================================
>--- Source/JavaScriptCore/ChangeLog	(revision 241267)
>+++ Source/JavaScriptCore/ChangeLog	(working copy)
>@@ -1,3 +1,26 @@
>+2019-02-11  Robin Morisset  <rmorisset@apple.com>
>+
>+        B3ReduceStrength::simplifyCFG() could do a lot more on each iteration
>+        https://bugs.webkit.org/show_bug.cgi?id=194475
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        B3ReduceStrength::simplifyCFG() does three optimizations (which I will call A, B and C):
>+        - A makes any terminal that points to a block that is empty except for a jump point to that jump's target instead.
>+        - B transforms any branch or switch that points to a single block into a jump
>+        - C finds blocks ending with jumps, whose successor has a single predecessor, and inline that successor block in place of the jump
>+
>+        It currently is limited in the following way:
>+        - A and C can only fire once per block per iteration
>+        - B can create jumps that would trigger A, but they may not be seen until the next iteration
>+
>+        Both problems are mitigated by going through the blocks in post-order, so that when a block is optimized most of its successors have already been optimized.
>+        In a sense it is the symmetric of the peephole optimizer that goes in pre-order so that when an instruction is optimized most of its children have already been optimized.
>+
>+        On JetStream2 it reduces the average number of iterations from 3.35 to 3.24.
>+
>+        * b3/B3ReduceStrength.cpp:
>+
> 2019-02-10  Mark Lam  <mark.lam@apple.com>
> 
>         Remove the RELEASE_ASSERT check for duplicate cases in the BinarySwitch constructor.
>Index: Source/JavaScriptCore/b3/B3ReduceStrength.cpp
>===================================================================
>--- Source/JavaScriptCore/b3/B3ReduceStrength.cpp	(revision 241267)
>+++ Source/JavaScriptCore/b3/B3ReduceStrength.cpp	(working copy)
>@@ -2376,7 +2376,7 @@ private:
>         // predecessors during strength reduction since that minimizes the total number of fixpoint
>         // iterations needed to kill a lot of code.
> 
>-        for (BasicBlock* block : m_proc) {
>+        for (BasicBlock* block : m_proc.blocksInPostOrder()) {
>             if (B3ReduceStrengthInternal::verbose)
>                 dataLog("Considering block ", *block, ":\n");
>

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