Modified: trunk/Source/_javascript_Core/ChangeLog (147510 => 147511)
--- trunk/Source/_javascript_Core/ChangeLog 2013-04-03 00:28:58 UTC (rev 147510)
+++ trunk/Source/_javascript_Core/ChangeLog 2013-04-03 00:34:31 UTC (rev 147511)
@@ -1,3 +1,31 @@
+2013-04-02 Geoffrey Garen <[email protected]>
+
+ DFG should compile a little sooner
+ https://bugs.webkit.org/show_bug.cgi?id=113835
+
+ Reviewed by Michael Saboff.
+
+ 2% speedup on SunSpider.
+
+ 2% speedup on JSRegress.
+
+ Neutral on Octane, v8, and Kraken.
+
+ The worst-hit single sub-test is kraken-stanford-crypto-ccm.js, which gets
+ 18% slower. Since Kraken is neutral overall in its preferred mean, I
+ think that's OK for now.
+
+ (Our array indexing speculation fails pathologically on
+ kraken-stanford-crypto-ccm.js. Compiling sooner is a regression because
+ it triggers those failures sooner. I'm going to file some follow-up bugs
+ explaining how to fix our speculations on this sub-test, at which point
+ compiling earlier should become a slight speedup on Kraken overall.)
+
+ * bytecode/CodeBlock.cpp:
+ (JSC::CodeBlock::optimizationThresholdScalingFactor): I experimented
+ with a few different options, including reducing the coefficient 'a'.
+ A simple linear reduction on instruction count worked best.
+
2013-04-01 Benjamin Poulain <[email protected]>
Use Vector::reserveInitialCapacity and Vector::uncheckedAppend for JSC's APIs
Modified: trunk/Source/_javascript_Core/bytecode/CodeBlock.cpp (147510 => 147511)
--- trunk/Source/_javascript_Core/bytecode/CodeBlock.cpp 2013-04-03 00:28:58 UTC (rev 147510)
+++ trunk/Source/_javascript_Core/bytecode/CodeBlock.cpp 2013-04-03 00:34:31 UTC (rev 147511)
@@ -2937,7 +2937,7 @@
double CodeBlock::optimizationThresholdScalingFactor()
{
- // This _expression_ arises from doing a least-squares fit of
+ // This _expression_ originally arose from doing a least-squares fit of
//
// F[x_] =: a * Sqrt[x + b] + Abs[c * x] + d
//
@@ -2951,8 +2951,13 @@
// 4000 5.5 (random large size, used to cause the function to converge to a shallow curve of some sort)
// 10000 6.0 (similar to above)
//
- // I achieve the minimization using the following Mathematica code:
+ // Since then, as compile times have gone down and optimization value has gone up, we've
+ // tweaked the function to favor earlier compilation.
//
+ // What follows is a complete description of how to reproduce the original coefficients:
+ //
+ // I achieved the minimization using the following Mathematica code:
+ //
// MyFunctionTemplate[x_, a_, b_, c_, d_] := a*Sqrt[x + b] + Abs[c*x] + d
//
// samples = {{10, 0.9}, {200, 1}, {320, 1.2}, {1268, 5}, {4000, 5.5}, {10000, 6}}
@@ -2991,21 +2996,23 @@
// the function turning over and going negative for large x) and I threw in a Sqrt
// term because Sqrt represents my intution that the function should be more sensitive
// to small changes in small values of x, but less sensitive when x gets large.
-
+ //
// Note that the current fit essentially eliminates the linear portion of the
// _expression_ (c == 0.0).
+
const double a = 0.061504;
const double b = 1.02406;
const double c = 0.0;
const double d = 0.825914;
+ const double instructionRatio = 0.8;
- double instructionCount = this->instructionCount();
+ double x = instructionCount() * instructionRatio;
- ASSERT(instructionCount); // Make sure this is called only after we have an instruction stream; otherwise it'll just return the value of d, which makes no sense.
+ ASSERT(x); // Make sure this is called only after we have an instruction stream; otherwise it'll just return the value of d, which makes no sense.
- double result = d + a * sqrt(instructionCount + b) + c * instructionCount;
+ double result = d + a * sqrt(x + b) + c * x;
#if ENABLE(JIT_VERBOSE_OSR)
- dataLog(*this, ": instruction count is ", instructionCount, ", scaling execution counter by ", result, " * ", codeTypeThresholdMultiplier(), "\n");
+ dataLog(*this, ": instruction count is ", instructionCount(), ", scaling execution counter by ", result, " * ", codeTypeThresholdMultiplier(), "\n");
#endif
return result * codeTypeThresholdMultiplier();
}
