[ARM] GlobalISel: Extract helper. NFCI.

Create a helper to deal with the common code for merging incoming values
together after they've been split during call lowering. There's likely
more stuff that can be commoned up here, but we'll leave that for later.

llvm-svn: 304143

1 files changed, 34 insertions, 29 deletions

diff --git a/llvm/lib/Target/ARM/ARMCallLowering.cpp b/llvm/lib/Target/ARM/ARMCallLowering.cpp
index 53087adf973..31a2f499a9a 100644
--- a/llvm/lib/Target/ARM/ARMCallLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMCallLowering.cpp
@@ -336,6 +336,26 @@ struct IncomingValueHandler : public CallLowering::ValueHandler {
     return 1;
   }
 
+  /// Merge the values in \p SrcRegs into \p DstReg at offsets \p SrcOffsets.
+  /// Note that the source registers are not required to have homogeneous types,
+  /// so we use G_INSERT rather than G_MERGE_VALUES.
+  // FIXME: Use G_MERGE_VALUES if the types are homogeneous.
+  void mergeRegisters(unsigned DstReg, ArrayRef<unsigned> SrcRegs,
+                      ArrayRef<uint64_t> SrcOffsets) {
+    LLT Ty = MRI.getType(DstReg);
+
+    unsigned Dst = MRI.createGenericVirtualRegister(Ty);
+    MIRBuilder.buildUndef(Dst);
+
+    for (unsigned i = 0; i < SrcRegs.size(); ++i) {
+      unsigned Tmp = MRI.createGenericVirtualRegister(Ty);
+      MIRBuilder.buildInsert(Tmp, Dst, SrcRegs[i], SrcOffsets[i]);
+      Dst = Tmp;
+    }
+
+    MIRBuilder.buildCopy(DstReg, Dst);
+  }
+
   /// Marking a physical register as used is different between formal
   /// parameters, where it's a basic block live-in, and call returns, where it's
   /// an implicit-def of the call instruction.
@@ -367,7 +387,6 @@ bool ARMCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   auto &MBB = MIRBuilder.getMBB();
   auto DL = MF.getDataLayout();
   auto &TLI = *getTLI<ARMTargetLowering>();
-  auto &MRI = MF.getRegInfo();
 
   auto Subtarget = TLI.getSubtarget();
 
@@ -381,29 +400,27 @@ bool ARMCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   CCAssignFn *AssignFn =
       TLI.CCAssignFnForCall(F.getCallingConv(), F.isVarArg());
 
+  FormalArgHandler ArgHandler(MIRBuilder, MIRBuilder.getMF().getRegInfo(),
+                              AssignFn);
+
   SmallVector<ArgInfo, 8> ArgInfos;
+  SmallVector<unsigned, 4> SplitRegs;
+  SmallVector<uint64_t, 4> RegOffsets;
   unsigned Idx = 0;
   for (auto &Arg : F.args()) {
     ArgInfo AInfo(VRegs[Idx], Arg.getType());
     setArgFlags(AInfo, Idx + AttributeList::FirstArgIndex, DL, F);
 
-    LLT Ty = MRI.getType(VRegs[Idx]);
-    bool Split = false;
-    unsigned Dst = VRegs[Idx];
+    SplitRegs.clear();
+    RegOffsets.clear();
+
     splitToValueTypes(AInfo, ArgInfos, MF, [&](unsigned Reg, uint64_t Offset) {
-      if (!Split) {
-        Split = true;
-        Dst = MRI.createGenericVirtualRegister(Ty);
-        MIRBuilder.buildUndef(Dst);
-      }
-      unsigned Tmp = MRI.createGenericVirtualRegister(Ty);
-      MIRBuilder.buildInsert(Tmp, Dst, Reg, Offset);
-      Dst = Tmp;
+      SplitRegs.push_back(Reg);
+      RegOffsets.push_back(Offset);
     });
-    if (Dst != VRegs[Idx]) {
-      assert(Split && "Destination changed but no split occured?");
-      MIRBuilder.buildCopy(VRegs[Idx], Dst);
-    }
+
+    if (!SplitRegs.empty())
+      ArgHandler.mergeRegisters(VRegs[Idx], SplitRegs, RegOffsets);
 
     Idx++;
   }
@@ -411,8 +428,6 @@ bool ARMCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   if (!MBB.empty())
     MIRBuilder.setInstr(*MBB.begin());
 
-  FormalArgHandler ArgHandler(MIRBuilder, MIRBuilder.getMF().getRegInfo(),
-                              AssignFn);
   return handleAssignments(MIRBuilder, ArgInfos, ArgHandler);
 }
 
@@ -493,17 +508,7 @@ bool ARMCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
     if (!RegOffsets.empty()) {
       // We have split the value and allocated each individual piece, now build
       // it up again.
-      LLT Ty = MRI.getType(OrigRet.Reg);
-      unsigned Dst = MRI.createGenericVirtualRegister(Ty);
-      MIRBuilder.buildUndef(Dst);
-
-      for (unsigned i = 0; i < SplitRegs.size(); ++i) {
-        unsigned Tmp = MRI.createGenericVirtualRegister(Ty);
-        MIRBuilder.buildInsert(Tmp, Dst, SplitRegs[i], RegOffsets[i]);
-        Dst = Tmp;
-      }
-
-      MIRBuilder.buildCopy(OrigRet.Reg, Dst);
+      RetHandler.mergeRegisters(OrigRet.Reg, SplitRegs, RegOffsets);
     }
   }