[PATCH] D80229: [Inlining] Set inline-deferral-scale to 2.

[Kazu Hirata via Phabricator via llvm-commits]

kazu created this revision.
kazu added a reviewer: davidxl.
Herald added subscribers: dexonsmith, hiraditya.
Herald added a project: LLVM.

This patch sets inline-deferral-scale to 2.

Both internal and SPEC benchmarking show that 2 is the best number
among -1, 2, 3, and 4.

inline-deferral-scale  SPECint2006
----------------------------------

  -1  38.0 (the default without this patch)
   2  38.5
   3  38.1
   4  38.1

With the new default number, shouldBeDeferred returns true if:

  TotalCost < IC.getCost() * 2

where

  TotalCost is TotalSecondaryCost + IC.getCost() * NumCallerUsers.

If TotalCost >= 0 and NumCallerUsers >= 2, then
TotalCost >= IC.getCost() * 2, so shouldBeDeferred returns true only
when NumCallerUsers is 1.

Now, if TotalSecondaryCost < 0, which can happen if
InlineConstants::LastCallToStaticBonus, a huge number, has been
subtracted from TotalSecondaryCost, then TotalCost may be negative.
In this case, shouldBeDeferred may return true even when
NumCallerUsers >= 2.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80229

Files:
  llvm/lib/Analysis/InlineAdvisor.cpp


Index: llvm/lib/Analysis/InlineAdvisor.cpp
===================================================================
--- llvm/lib/Analysis/InlineAdvisor.cpp
+++ llvm/lib/Analysis/InlineAdvisor.cpp
@@ -45,7 +45,7 @@
 static cl::opt<int>
     InlineDeferralScale("inline-deferral-scale",
                         cl::desc("Scale to limit the cost of inline deferral"),
-                        cl::init(-1), cl::Hidden);
+                        cl::init(2), cl::Hidden);
 
 namespace {
 class DefaultInlineAdvice : public InlineAdvice {


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