Attachment 361614 Details for Bug 194475 – Patch

[patch] Patch

bug-194475-20190209153137.patch (text/plain), 2.44 KB, created by Robin Morisset on 2019-02-09 15:31:38 PST

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Creator: Robin Morisset

Created: 2019-02-09 15:31:38 PST

Size: 2.44 KB

patch

obsolete

>Subversion Revision: 241245
>diff --git a/Source/JavaScriptCore/ChangeLog b/Source/JavaScriptCore/ChangeLog
>index c6fe0ea3d9f95608c27b23704db6f9eed2c124ae..90b81103f32e46a7ef0afe97f7b0e4ff9b94acf5 100644
>--- a/Source/JavaScriptCore/ChangeLog
>+++ b/Source/JavaScriptCore/ChangeLog
>@@ -1,3 +1,26 @@
>+2019-02-09  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 CFGa, CFGb and CFGc):
>+        - CFGa makes any terminal that points to a block empty except for a jump point to that jump instead.
>+        - CFGb transforms any branch or switch that point to a single block into a jump
>+        - CFGc inlines any block with a single predecessor that ends in a jump into the end of that predecessor.
>+
>+        It currently is limited in the following way:
>+        - CFGa and CFGc can only fire once per block per iteration
>+        - CFGb can create jumps that would trigger CFGa, 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:
>+
> 2019-02-09  Darin Adler  <darin@apple.com>
> 
>         Eliminate unnecessary String temporaries by using StringConcatenateNumbers
>diff --git a/Source/JavaScriptCore/b3/B3ReduceStrength.cpp b/Source/JavaScriptCore/b3/B3ReduceStrength.cpp
>index 7690b53de8d9f557f7118afdb0cad2e1a6a2ccbb..cea51443beb7c39b9eda727b5ba612728db0837c 100644
>--- a/Source/JavaScriptCore/b3/B3ReduceStrength.cpp
>+++ b/Source/JavaScriptCore/b3/B3ReduceStrength.cpp
>@@ -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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