[EVM][InlineCost] Set threshold to a small value when BB is unreachable-terminated

For EVM, to return from the contract we are using
different instructions (e.g. return, revert) which
are followed by unreachable. In the Inliner heuristic,
if BB is unreachable-terminated threshold is set to 0
and these callsites are unlikely to be inlined. Instead,
add small threshold and continue to calculate cost model,
since in some cases we benefit from inlining.

Signed-off-by: Vladimir Radosavljevic <[email protected]>

Author: vladimirradosavljevic

llvm/lib/Analysis/InlineCost.cpp

@@ -1911,8 +1911,13 @@ InlineCostCallAnalyzer::getHotCallSiteThreshold(CallBase &Call,
 void InlineCostCallAnalyzer::updateThreshold(CallBase &Call, Function &Callee) {
   // If no size growth is allowed for this inlining, set Threshold to 0.
   if (!allowSizeGrowth(Call)) {
-    Threshold = 0;
-    return;
+    if (Triple(Call.getFunction()->getParent()->getTargetTriple()).isEVM()) {
+      constexpr int UnreachableThreshold = 10;
+      Threshold = std::min(Threshold, UnreachableThreshold);
+    } else {
+      Threshold = 0;
+      return;
+    }
   }
 
   Function *Caller = Call.getCaller();