GlobalISel: legalize G_INSERT instructions

We don't handle all cases yet (see arm64-fallback.ll for an example), but this
is enough to cover most common C++ code so it's a good place to start.

llvm-svn: 294247

2 files changed, 91 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 6da02646250..27b6dc755a2 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -119,6 +119,17 @@ LegalizerHelper::libcall(MachineInstr &MI) {
   }
 }
 
+void LegalizerHelper::findInsertionsForRange(
+    int64_t DstStart, int64_t DstEnd, MachineInstr::mop_iterator &CurOp,
+    MachineInstr::mop_iterator &EndOp, MachineInstr &MI) {
+  while (CurOp != MI.operands_end() && std::next(CurOp)->getImm() < DstStart)
+    CurOp += 2;
+
+  EndOp = CurOp;
+  while (EndOp != MI.operands_end() && std::next(EndOp)->getImm() < DstEnd)
+    EndOp += 2;
+}
+
 LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
                                                               unsigned TypeIdx,
                                                               LLT NarrowTy) {
@@ -161,6 +172,65 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_INSERT: {
+    if (TypeIdx != 0)
+      return UnableToLegalize;
+
+    unsigned NarrowSize = NarrowTy.getSizeInBits();
+    int NumParts =
+        MRI.getType(MI.getOperand(0).getReg()).getSizeInBits() / NarrowSize;
+
+    SmallVector<unsigned, 2> SrcRegs, DstRegs;
+    SmallVector<uint64_t, 2> Indexes;
+    extractParts(MI.getOperand(1).getReg(), NarrowTy, NumParts, SrcRegs);
+
+    MachineInstr::mop_iterator CurOp = MI.operands_begin() + 2, EndOp;
+    for (int i = 0; i < NumParts; ++i) {
+      unsigned DstStart = i * NarrowSize;
+      unsigned DstReg = MRI.createGenericVirtualRegister(NarrowTy);
+      Indexes.push_back(DstStart);
+
+      findInsertionsForRange(DstStart, DstStart + NarrowSize, CurOp, EndOp, MI);
+
+      if (CurOp == EndOp) {
+        // No part of the insert affects this subregister, forward the original.
+        DstRegs.push_back(SrcRegs[i]);
+        continue;
+      } else if (MRI.getType(CurOp->getReg()) == NarrowTy &&
+                 std::next(CurOp)->getImm() == DstStart) {
+        // The entire subregister is defined by this insert, forward the new
+        // value.
+        DstRegs.push_back(CurOp->getReg());
+        continue;
+      }
+
+      auto MIB = MIRBuilder.buildInstr(TargetOpcode::G_INSERT)
+        .addDef(DstReg)
+        .addUse(SrcRegs[i]);
+
+      for (; CurOp != EndOp; CurOp += 2) {
+        unsigned Reg = CurOp->getReg();
+        uint64_t Offset = std::next(CurOp)->getImm() - DstStart;
+
+        // Make sure we don't have a cross-register insert.
+        if (Offset + MRI.getType(Reg).getSizeInBits() > NarrowSize) {
+          // FIXME: we should handle this case, though it's unlikely to be
+          // common given ABI-related layout restrictions.
+          return UnableToLegalize;
+        }
+
+        MIB.addUse(Reg);
+        MIB.addImm(Offset);
+      }
+
+      DstRegs.push_back(DstReg);
+    }
+
+    assert(DstRegs.size() == (unsigned)NumParts && "not all parts covered");
+    MIRBuilder.buildSequence(MI.getOperand(0).getReg(), DstRegs, Indexes);
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_LOAD: {
     unsigned NarrowSize = NarrowTy.getSizeInBits();
     int NumParts =
@@ -309,6 +379,26 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_INSERT: {
+    if (TypeIdx != 0)
+      return UnableToLegalize;
+
+    unsigned Src = MI.getOperand(1).getReg();
+    unsigned SrcExt = MRI.createGenericVirtualRegister(WideTy);
+    MIRBuilder.buildAnyExt(SrcExt, Src);
+
+    unsigned DstExt = MRI.createGenericVirtualRegister(WideTy);
+    auto MIB = MIRBuilder.buildInsert(DstExt, SrcExt, MI.getOperand(2).getReg(),
+                                      MI.getOperand(3).getImm());
+    for (unsigned OpNum = 4; OpNum < MI.getNumOperands(); OpNum += 2) {
+      MIB.addReg(MI.getOperand(OpNum).getReg());
+      MIB.addImm(MI.getOperand(OpNum + 1).getImm());
+    }
+
+    MIRBuilder.buildTrunc(MI.getOperand(0).getReg(), DstExt);
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_LOAD: {
     assert(alignTo(MRI.getType(MI.getOperand(0).getReg()).getSizeInBits(), 8) ==
                WideTy.getSizeInBits() &&
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
index e49662075ed..e757f2587ac 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
@@ -41,6 +41,7 @@ LegalizerInfo::LegalizerInfo() : TablesInitialized(false) {
   DefaultActions[TargetOpcode::G_STORE] = NarrowScalar;
 
   DefaultActions[TargetOpcode::G_BRCOND] = WidenScalar;
+  DefaultActions[TargetOpcode::G_INSERT] = NarrowScalar;
 }
 
 void LegalizerInfo::computeTables() {