[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 +1911,15 @@ 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;
+    // EVM local change begin
+    if (Triple(Call.getFunction()->getParent()->getTargetTriple()).isEVM()) {
+      constexpr int UnreachableThreshold = 10;
+      Threshold = std::min(Threshold, UnreachableThreshold);
+    } else {
+      Threshold = 0;
+      return;
+    }
+    // EVM local change end
   }
 
   Function *Caller = Call.getCaller();

llvm/test/CodeGen/EVM/inline-in-bb-unreachable-terminated.ll

@@ -3,7 +3,7 @@
 target datalayout = "E-p:256:256-i256:256:256-S256-a:256:256"
 target triple = "evm"
 
-; CHECK-LABEL: define private void @callee_inline
+; CHECK-NOT: define private void @callee_inline
 define private void @callee_inline(i256 %arg) {
 entry:
   %itptr = inttoptr i256 %arg to ptr addrspace(5)
@@ -24,7 +24,7 @@ bb2:
 ; CHECK-LABEL: define void @caller_inline1
 define void @caller_inline1(i256 %arg) {
 entry:
-; CHECK: call void @callee_inline(i256 %arg)
+; CHECK-NOT: call void @callee_inline(i256 %arg)
   call void @callee_inline(i256 %arg)
   %itptr = inttoptr i256 %arg to ptr addrspace(5)
   %load = load i256, ptr addrspace(5) %itptr, align 1
@@ -36,7 +36,7 @@ entry:
 ; CHECK-LABEL: define void @caller_inline2
 define void @caller_inline2(i256 %arg1, i256 %arg2) {
 entry:
-; CHECK: call void @callee_inline(i256 %arg2)
+; CHECK-NOT: call void @callee_inline(i256 %arg2)
   call void @callee_inline(i256 %arg2)
   %itptr = inttoptr i256 %arg2 to ptr addrspace(5)
   %load = load i256, ptr addrspace(5) %itptr, align 1