Lower @llvm.experimental.deoptimize as a noreturn call
While preserving the return value for @llvm.experimental.deoptimize at
the IR level is useful during mid-level optimization, doing so at the
machine instruction level requires generating some extra code and a
return that is non-ideal. This change has LLVM lower
```
%val = call @llvm.experimental.deoptimize
ret %val
```
to effectively
```
call @__llvm_deoptimize()
unreachable
```
instead.
llvm-svn: 265502
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 91c0a04..f6b4262 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1377,6 +1377,18 @@
SmallVector<ISD::OutputArg, 8> Outs;
SmallVector<SDValue, 8> OutVals;
+ // Calls to @llvm.experimental.deoptimize don't generate a return value, so
+ // lower
+ //
+ // %val = call <ty> @llvm.experimental.deoptimize()
+ // ret <ty> %val
+ //
+ // differently.
+ if (I.getParent()->getTerminatingDeoptimizeCall()) {
+ LowerDeoptimizingReturn();
+ return;
+ }
+
if (!FuncInfo.CanLowerReturn) {
unsigned DemoteReg = FuncInfo.DemoteRegister;
const Function *F = I.getParent()->getParent();
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 214c510..2d20026 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -779,10 +779,12 @@
const BasicBlock *EHPadBB);
void LowerDeoptimizeCall(const CallInst *CI);
+ void LowerDeoptimizingReturn();
void LowerCallSiteWithDeoptBundleImpl(ImmutableCallSite CS, SDValue Callee,
const BasicBlock *EHPadBB,
- bool VarArgDisallowed);
+ bool VarArgDisallowed,
+ bool ForceVoidReturnTy);
private:
// Terminator instructions.
diff --git a/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
index edec366..f489e3b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
@@ -823,11 +823,13 @@
void SelectionDAGBuilder::LowerCallSiteWithDeoptBundleImpl(
ImmutableCallSite CS, SDValue Callee, const BasicBlock *EHPadBB,
- bool VarArgDisallowed) {
+ bool VarArgDisallowed, bool ForceVoidReturnTy) {
StatepointLoweringInfo SI(DAG);
unsigned ArgBeginIndex = CS.arg_begin() - CS.getInstruction()->op_begin();
- populateCallLoweringInfo(SI.CLI, CS, ArgBeginIndex, CS.getNumArgOperands(),
- Callee, CS.getType(), false);
+ populateCallLoweringInfo(
+ SI.CLI, CS, ArgBeginIndex, CS.getNumArgOperands(), Callee,
+ ForceVoidReturnTy ? Type::getVoidTy(*DAG.getContext()) : CS.getType(),
+ false);
if (!VarArgDisallowed)
SI.CLI.IsVarArg = CS.getFunctionType()->isVarArg();
@@ -856,7 +858,8 @@
void SelectionDAGBuilder::LowerCallSiteWithDeoptBundle(
ImmutableCallSite CS, SDValue Callee, const BasicBlock *EHPadBB) {
LowerCallSiteWithDeoptBundleImpl(CS, Callee, EHPadBB,
- /* VarArgDisallowed = */ false);
+ /* VarArgDisallowed = */ false,
+ /* ForceVoidReturnTy = */ false);
}
void SelectionDAGBuilder::visitGCResult(const CallInst &CI) {
@@ -941,7 +944,18 @@
TLI.getPointerTy(DAG.getDataLayout()));
// We don't lower calls to __llvm_deoptimize as varargs, but as a regular
- // call.
+ // call. We also do not lower the return value to any virtual register, and
+ // change the immediately following return to a trap instruction.
LowerCallSiteWithDeoptBundleImpl(CI, Callee, /* EHPadBB = */ nullptr,
- /* VarArgDisallowed = */ true);
+ /* VarArgDisallowed = */ true,
+ /* ForceVoidReturnTy = */ true);
+}
+
+void SelectionDAGBuilder::LowerDeoptimizingReturn() {
+ // We do not lower the return value from llvm.deoptimize to any virtual
+ // register, and change the immediately following return to a trap
+ // instruction.
+ if (DAG.getTarget().Options.TrapUnreachable)
+ DAG.setRoot(
+ DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
}