[llvm] cec20db - [Inlining] Set inline-deferral-scale to 2.

[Kazu Hirata via llvm-commits]

Author: Kazu Hirata
Date: 2020-05-25T15:44:20-07:00
New Revision: cec20db588254289dc2953517310b9886f6dc243

URL: https://github.com/llvm/llvm-project/commit/cec20db588254289dc2953517310b9886f6dc243
DIFF: https://github.com/llvm/llvm-project/commit/cec20db588254289dc2953517310b9886f6dc243.diff

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

Summary:
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.

Reviewers: davidxl, nikic

Reviewed By: davidxl

Subscribers: xbolva00, hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80229

Added: 
    

Modified: 
    llvm/lib/Analysis/InlineAdvisor.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/InlineAdvisor.cpp b/llvm/lib/Analysis/InlineAdvisor.cpp
index dcaf9d0fea74..ac3ba451aa3f 100644
--- a/llvm/lib/Analysis/InlineAdvisor.cpp
+++ b/llvm/lib/Analysis/InlineAdvisor.cpp
@@ -45,7 +45,7 @@ static cl::opt<bool>
 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 {