[EVM][InlineCost] When BB is unreachable-terminated allow inlining

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();