bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
// We model unconditional switches as free, see the comments on handling
// branches.
- return isa<ConstantInt>(SI.getCondition()) ||
- dyn_cast_or_null<ConstantInt>(
- SimplifiedValues.lookup(SI.getCondition()));
+ if (isa<ConstantInt>(SI.getCondition()))
+ return true;
+ if (Value *V = SimplifiedValues.lookup(SI.getCondition()))
+ if (isa<ConstantInt>(V))
+ return true;
+
+ // Otherwise, we need to accumulate a cost proportional to the number of
+ // distinct successor blocks. This fan-out in the CFG cannot be represented
+ // for free even if we can represent the core switch as a jumptable that
+ // takes a single instruction.
+ //
+ // NB: We convert large switches which are just used to initialize large phi
+ // nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent
+ // inlining those. It will prevent inlining in cases where the optimization
+ // does not (yet) fire.
+ SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
+ SuccessorBlocks.insert(SI.getDefaultDest());
+ for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
+ SuccessorBlocks.insert(I.getCaseSuccessor());
+ // Add cost corresponding to the number of distinct destinations. The first
+ // we model as free because of fallthrough.
+ Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
+ return false;
}
bool CallAnalyzer::visitIndirectBrInst(IndirectBrInst &IBI) {
--- /dev/null
+; RUN: opt < %s -inline -inline-threshold=20 -S | FileCheck %s
+
+define i32 @callee(i32 %a) {
+ switch i32 %a, label %sw.default [
+ i32 0, label %sw.bb0
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ i32 3, label %sw.bb3
+ i32 4, label %sw.bb4
+ i32 5, label %sw.bb5
+ i32 6, label %sw.bb6
+ i32 7, label %sw.bb7
+ i32 8, label %sw.bb8
+ i32 9, label %sw.bb9
+ ]
+
+sw.default:
+ br label %return
+
+sw.bb0:
+ br label %return
+
+sw.bb1:
+ br label %return
+
+sw.bb2:
+ br label %return
+
+sw.bb3:
+ br label %return
+
+sw.bb4:
+ br label %return
+
+sw.bb5:
+ br label %return
+
+sw.bb6:
+ br label %return
+
+sw.bb7:
+ br label %return
+
+sw.bb8:
+ br label %return
+
+sw.bb9:
+ br label %return
+
+return:
+ ret i32 42
+}
+
+define i32 @caller(i32 %a) {
+; CHECK-LABEL: @caller(
+; CHECK: call i32 @callee(
+
+ %result = call i32 @callee(i32 %a)
+ ret i32 %result
+}