[InlineCost] Add flag to allow changing the default inline cost

Summary:
It can be useful to tune the default inline threshold without overriding other inlining thresholds (e.g. in code compiled for size).

The existing `-inline-threshold` flag overrides other thresholds, so it is insufficient in codebases where there is a mix of code compiled for size and speed.

Patch by Michael Holman <michael.holman@microsoft.com>

Reviewers: eraman, tejohnson

Reviewed By: tejohnson

Subscribers: tejohnson, mtrofin, davidxl, hiraditya, haicheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73217

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index 49014e8..98ece45 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -46,6 +46,11 @@ using namespace llvm;
 
 STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed");
 
+static cl::opt<int>
+    DefaultThreshold("inlinedefault-threshold", cl::Hidden, cl::init(225),
+                     cl::ZeroOrMore,
+                     cl::desc("Default amount of inlining to perform"));
+
 static cl::opt<int> InlineThreshold(
     "inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
     cl::desc("Control the amount of inlining to perform (default = 225)"));
@@ -2303,7 +2308,7 @@ InlineParams llvm::getInlineParams(int Threshold) {
 }
 
 InlineParams llvm::getInlineParams() {
-  return getInlineParams(InlineThreshold);
+  return getInlineParams(DefaultThreshold);
 }
 
 // Compute the default threshold for inlining based on the opt level and the
@@ -2316,7 +2321,7 @@ static int computeThresholdFromOptLevels(unsigned OptLevel,
     return InlineConstants::OptSizeThreshold;
   if (SizeOptLevel == 2) // -Oz
     return InlineConstants::OptMinSizeThreshold;
-  return InlineThreshold;
+  return DefaultThreshold;
 }
 
 InlineParams llvm::getInlineParams(unsigned OptLevel, unsigned SizeOptLevel) {