Only pass 'returned' to target-specific lowering code when the value of entire register is guaranteed to be preserved.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180825 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 42 insertions, 24 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 6e613d606f..5eeac5b11f 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -6398,6 +6398,28 @@ void SelectionDAGBuilder::visitVACopy(const CallInst &I) {
 /// migrated to using LowerCall, this hook should be integrated into SDISel.
 std::pair<SDValue, SDValue>
 TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
+  // Handle the incoming return values from the call.
+  CLI.Ins.clear();
+  SmallVector<EVT, 4> RetTys;
+  ComputeValueVTs(*this, CLI.RetTy, RetTys);
+  for (unsigned I = 0, E = RetTys.size(); I != E; ++I) {
+    EVT VT = RetTys[I];
+    MVT RegisterVT = getRegisterType(CLI.RetTy->getContext(), VT);
+    unsigned NumRegs = getNumRegisters(CLI.RetTy->getContext(), VT);
+    for (unsigned i = 0; i != NumRegs; ++i) {
+      ISD::InputArg MyFlags;
+      MyFlags.VT = RegisterVT;
+      MyFlags.Used = CLI.IsReturnValueUsed;
+      if (CLI.RetSExt)
+        MyFlags.Flags.setSExt();
+      if (CLI.RetZExt)
+        MyFlags.Flags.setZExt();
+      if (CLI.IsInReg)
+        MyFlags.Flags.setInReg();
+      CLI.Ins.push_back(MyFlags);
+    }
+  }
+
   // Handle all of the outgoing arguments.
   CLI.Outs.clear();
   CLI.OutVals.clear();
@@ -6439,8 +6461,6 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
       }
       if (Args[i].isNest)
         Flags.setNest();
-      if (Args[i].isReturned)
-        Flags.setReturned();
       Flags.setOrigAlign(OriginalAlignment);
 
       MVT PartVT = getRegisterType(CLI.RetTy->getContext(), VT);
@@ -6453,6 +6473,26 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
       else if (Args[i].isZExt)
         ExtendKind = ISD::ZERO_EXTEND;
 
+      // Conservatively only handle 'returned' on non-vectors for now
+      if (Args[i].isReturned && !Op.getValueType().isVector()) {
+        assert(CLI.RetTy == Args[i].Ty && RetTys.size() == NumValues &&
+               "unexpected use of 'returned'");
+        // Before passing 'returned' to the target lowering code, ensure that
+        // either the register MVT and the actual EVT are the same size or that
+        // the return value and argument are extended in the same way; in these
+        // cases it's safe to pass the argument register value unchanged as the
+        // return register value (although it's at the target's option whether
+        // to do so)
+        // TODO: allow code generation to take advantage of partially preserved
+        // registers rather than clobbering the entire register when the
+        // parameter extension method is not compatible with the return
+        // extension method
+        if ((NumParts * PartVT.getSizeInBits() == VT.getSizeInBits()) ||
+            (ExtendKind != ISD::ANY_EXTEND &&
+             CLI.RetSExt == Args[i].isSExt && CLI.RetZExt == Args[i].isZExt))
+        Flags.setReturned();
+      }
+
       getCopyToParts(CLI.DAG, CLI.DL, Op, &Parts[0], NumParts,
                      PartVT, CLI.CS ? CLI.CS->getInstruction() : 0, ExtendKind);
 
@@ -6472,28 +6512,6 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
     }
   }
 
-  // Handle the incoming return values from the call.
-  CLI.Ins.clear();
-  SmallVector<EVT, 4> RetTys;
-  ComputeValueVTs(*this, CLI.RetTy, RetTys);
-  for (unsigned I = 0, E = RetTys.size(); I != E; ++I) {
-    EVT VT = RetTys[I];
-    MVT RegisterVT = getRegisterType(CLI.RetTy->getContext(), VT);
-    unsigned NumRegs = getNumRegisters(CLI.RetTy->getContext(), VT);
-    for (unsigned i = 0; i != NumRegs; ++i) {
-      ISD::InputArg MyFlags;
-      MyFlags.VT = RegisterVT;
-      MyFlags.Used = CLI.IsReturnValueUsed;
-      if (CLI.RetSExt)
-        MyFlags.Flags.setSExt();
-      if (CLI.RetZExt)
-        MyFlags.Flags.setZExt();
-      if (CLI.IsInReg)
-        MyFlags.Flags.setInReg();
-      CLI.Ins.push_back(MyFlags);
-    }
-  }
-
   SmallVector<SDValue, 4> InVals;
   CLI.Chain = LowerCall(CLI, InVals);