[NewPM][Inliner] Make inlined calls to functions in same SCC as callee exponentially expensive

Introduce a new attribute "function-inline-cost-multiplier" which
multiplies the inline cost of a call site (or all calls to a callee) by
the multiplier.

When processing the list of calls created by inlining, check each call
to see if the new call's callee is in the same SCC as the original
callee. If so, set the "function-inline-cost-multiplier" attribute of
the new call site to double the original call site's attribute value.
This does not happen when the original call site is intra-SCC.

This is an alternative to D120584, which marks the call sites as
noinline.

Hopefully fixes PR45253.

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D121084

1 files changed, 11 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index e21f2e2..b0fae1b 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -133,8 +133,6 @@ static cl::opt<bool> DisableGEPConstOperand(
     cl::desc("Disables evaluation of GetElementPtr with constant operands"));
 
 namespace {
-class InlineCostCallAnalyzer;
-
 /// This function behaves more like CallBase::hasFnAttr: when it looks for the
 /// requested attribute, it check both the call instruction and the called
 /// function (if it's available and operand bundles don't prohibit that).
@@ -151,7 +149,9 @@ Attribute getFnAttr(CallBase &CB, StringRef AttrKind) {
 
   return {};
 }
+} // namespace
 
+namespace llvm {
 Optional<int> getStringFnAttrAsInt(CallBase &CB, StringRef AttrKind) {
   Attribute Attr = getFnAttr(CB, AttrKind);
   int AttrValue;
@@ -159,6 +159,10 @@ Optional<int> getStringFnAttrAsInt(CallBase &CB, StringRef AttrKind) {
     return None;
   return AttrValue;
 }
+} // namespace llvm
+
+namespace {
+class InlineCostCallAnalyzer;
 
 // This struct is used to store information about inline cost of a
 // particular instruction
@@ -904,6 +908,11 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
             getStringFnAttrAsInt(CandidateCall, "function-inline-cost"))
       Cost = *AttrCost;
 
+    if (Optional<int> AttrCostMult = getStringFnAttrAsInt(
+            CandidateCall,
+            InlineConstants::FunctionInlineCostMultiplierAttributeName))
+      Cost *= *AttrCostMult;
+
     if (Optional<int> AttrThreshold =
             getStringFnAttrAsInt(CandidateCall, "function-inline-threshold"))
       Threshold = *AttrThreshold;