[globalisel][tablegen] Add support for EXTRACT_SUBREG.

Summary:
After this patch, we finally have test cases that require multiple
instruction emission.

Depends on D33590

Reviewers: ab, qcolombet, t.p.northover, rovka, kristof.beyls

Subscribers: javed.absar, llvm-commits, igorb

Differential Revision: https://reviews.llvm.org/D33596

llvm-svn: 306388

1 files changed, 142 insertions, 9 deletions

diff --git a/llvm/utils/TableGen/GlobalISelEmitter.cpp b/llvm/utils/TableGen/GlobalISelEmitter.cpp
index 03d231a153d..50da9085c21 100644
--- a/llvm/utils/TableGen/GlobalISelEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelEmitter.cpp
@@ -832,7 +832,13 @@ public:
 //===- Actions ------------------------------------------------------------===//
 class OperandRenderer {
 public:
-  enum RendererKind { OR_Copy, OR_Imm, OR_Register, OR_ComplexPattern };
+  enum RendererKind {
+    OR_Copy,
+    OR_CopySubReg,
+    OR_Imm,
+    OR_Register,
+    OR_ComplexPattern
+  };
 
 protected:
   RendererKind Kind;
@@ -877,6 +883,42 @@ public:
   }
 };
 
+/// A CopySubRegRenderer emits code to copy a single register operand from an
+/// existing instruction to the one being built and indicate that only a
+/// subregister should be copied.
+class CopySubRegRenderer : public OperandRenderer {
+protected:
+  /// The matcher for the instruction that this operand is copied from.
+  /// This provides the facility for looking up an a operand by it's name so
+  /// that it can be used as a source for the instruction being built.
+  const InstructionMatcher &Matched;
+  /// The name of the operand.
+  const StringRef SymbolicName;
+  /// The subregister to extract.
+  const CodeGenSubRegIndex *SubReg;
+
+public:
+  CopySubRegRenderer(const InstructionMatcher &Matched, StringRef SymbolicName,
+                     const CodeGenSubRegIndex *SubReg)
+      : OperandRenderer(OR_CopySubReg), Matched(Matched),
+        SymbolicName(SymbolicName), SubReg(SubReg) {}
+
+  static bool classof(const OperandRenderer *R) {
+    return R->getKind() == OR_CopySubReg;
+  }
+
+  const StringRef getSymbolicName() const { return SymbolicName; }
+
+  void emitCxxRenderStmts(raw_ostream &OS, RuleMatcher &Rule) const override {
+    const OperandMatcher &Operand = Matched.getOperand(SymbolicName);
+    StringRef InsnVarName =
+        Rule.getInsnVarName(Operand.getInstructionMatcher());
+    std::string OperandExpr = Operand.getOperandExpr(InsnVarName);
+    OS << "    MIB.addReg(" << OperandExpr << ".getReg() /*" << SymbolicName
+       << "*/, 0, " << SubReg->EnumValue << ");\n";
+  }
+};
+
 /// Adds a specific physical register to the instruction being built.
 /// This is typically useful for WZR/XZR on AArch64.
 class AddRegisterRenderer : public OperandRenderer {
@@ -1292,6 +1334,7 @@ private:
   const RecordKeeper &RK;
   const CodeGenDAGPatterns CGP;
   const CodeGenTarget &Target;
+  CodeGenRegBank CGRegs;
 
   /// Keep track of the equivalence between SDNodes and Instruction.
   /// This is defined using 'GINodeEquiv' in the target description.
@@ -1315,9 +1358,9 @@ private:
   Error importChildMatcher(InstructionMatcher &InsnMatcher,
                            const TreePatternNode *SrcChild, unsigned OpIdx,
                            unsigned &TempOpIdx) const;
-  Expected<BuildMIAction &> createAndImportInstructionRenderer(
-      RuleMatcher &M, const TreePatternNode *Dst,
-      const InstructionMatcher &InsnMatcher) const;
+  Expected<BuildMIAction &>
+  createAndImportInstructionRenderer(RuleMatcher &M, const TreePatternNode *Dst,
+                                     const InstructionMatcher &InsnMatcher);
   Error importExplicitUseRenderer(BuildMIAction &DstMIBuilder,
                                   TreePatternNode *DstChild,
                                   const InstructionMatcher &InsnMatcher) const;
@@ -1354,7 +1397,7 @@ const CodeGenInstruction *GlobalISelEmitter::findNodeEquiv(Record *N) const {
 }
 
 GlobalISelEmitter::GlobalISelEmitter(RecordKeeper &RK)
-    : RK(RK), CGP(RK), Target(CGP.getTargetInfo()) {}
+    : RK(RK), CGP(RK), Target(CGP.getTargetInfo()), CGRegs(RK) {}
 
 //===- Emitter ------------------------------------------------------------===//
 
@@ -1585,7 +1628,7 @@ Error GlobalISelEmitter::importExplicitUseRenderer(
 
 Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
     RuleMatcher &M, const TreePatternNode *Dst,
-    const InstructionMatcher &InsnMatcher) const {
+    const InstructionMatcher &InsnMatcher) {
   Record *DstOp = Dst->getOperator();
   if (!DstOp->isSubClassOf("Instruction")) {
     if (DstOp->isSubClassOf("ValueType"))
@@ -1597,13 +1640,17 @@ Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
 
   unsigned DstINumUses = DstI->Operands.size() - DstI->Operands.NumDefs;
   unsigned ExpectedDstINumUses = Dst->getNumChildren();
+  bool IsExtractSubReg = false;
 
   // COPY_TO_REGCLASS is just a copy with a ConstrainOperandToRegClassAction
-  // attached.
+  // attached. Similarly for EXTRACT_SUBREG except that's a subregister copy.
   if (DstI->TheDef->getName() == "COPY_TO_REGCLASS") {
     DstI = &Target.getInstruction(RK.getDef("COPY"));
     DstINumUses--; // Ignore the class constraint.
     ExpectedDstINumUses--;
+  } else if (DstI->TheDef->getName() == "EXTRACT_SUBREG") {
+    DstI = &Target.getInstruction(RK.getDef("COPY"));
+    IsExtractSubReg = true;
   }
 
   auto &DstMIBuilder = M.addAction<BuildMIAction>("NewI", DstI, InsnMatcher);
@@ -1614,6 +1661,32 @@ Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
     DstMIBuilder.addRenderer<CopyRenderer>(InsnMatcher, DstIOperand.Name);
   }
 
+  // EXTRACT_SUBREG needs to use a subregister COPY.
+  if (IsExtractSubReg) {
+    if (!Dst->getChild(0)->isLeaf())
+      return failedImport("EXTRACT_SUBREG child #1 is not a leaf");
+
+    if (DefInit *SubRegInit = dyn_cast<DefInit>(Dst->getChild(1)->getLeafValue())) {
+      CodeGenRegisterClass *RC = CGRegs.getRegClass(
+          getInitValueAsRegClass(Dst->getChild(0)->getLeafValue()));
+      CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
+
+      const auto &SrcRCDstRCPair =
+          RC->getMatchingSubClassWithSubRegs(CGRegs, SubIdx);
+      if (SrcRCDstRCPair.hasValue()) {
+        assert(SrcRCDstRCPair->second && "Couldn't find a matching subclass");
+        if (SrcRCDstRCPair->first != RC)
+          return failedImport("EXTRACT_SUBREG requires an additional COPY");
+      }
+
+      DstMIBuilder.addRenderer<CopySubRegRenderer>(
+          InsnMatcher, Dst->getChild(0)->getName(), SubIdx);
+      return DstMIBuilder;
+    }
+
+    return failedImport("EXTRACT_SUBREG child #1 is not a subreg index");
+  }
+
   // Render the explicit uses.
   unsigned Child = 0;
   unsigned NumDefaultOps = 0;
@@ -1740,6 +1813,16 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
       if (DstIOpRec == nullptr)
         return failedImport(
             "COPY_TO_REGCLASS operand #1 isn't a register class");
+    } else if (DstI.TheDef->getName() == "EXTRACT_SUBREG") {
+      if (!Dst->getChild(0)->isLeaf())
+        return failedImport("EXTRACT_SUBREG operand #0 isn't a leaf");
+
+      // We can assume that a subregister is in the same bank as it's super register.
+      DstIOpRec = getInitValueAsRegClass(Dst->getChild(0)->getLeafValue());
+
+      if (DstIOpRec == nullptr)
+        return failedImport(
+            "EXTRACT_SUBREG operand #0 isn't a register class");
     } else if (DstIOpRec->isSubClassOf("RegisterOperand"))
       DstIOpRec = DstIOpRec->getValueAsDef("RegClass");
     else if (!DstIOpRec->isSubClassOf("RegisterClass"))
@@ -1776,8 +1859,58 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
 
     M.addAction<ConstrainOperandToRegClassAction>(
         "NewI", 0, Target.getRegisterClass(DstIOpRec));
-  } else
-    M.addAction<ConstrainOperandsToDefinitionAction>("NewI");
+
+    // We're done with this pattern!  It's eligible for GISel emission; return
+    // it.
+    ++NumPatternImported;
+    return std::move(M);
+  }
+
+  if (DstI.TheDef->getName() == "EXTRACT_SUBREG") {
+    // EXTRACT_SUBREG selects into a subregister COPY but unlike most
+    // instructions, the result register class is controlled by the
+    // subregisters of the operand. As a result, we must constrain the result
+    // class rather than check that it's already the right one.
+    if (!Dst->getChild(0)->isLeaf())
+      return failedImport("EXTRACT_SUBREG child #1 is not a leaf");
+
+    if (DefInit *SubRegInit =
+            dyn_cast<DefInit>(Dst->getChild(1)->getLeafValue())) {
+      // Constrain the result to the same register bank as the operand.
+      Record *DstIOpRec =
+          getInitValueAsRegClass(Dst->getChild(0)->getLeafValue());
+
+      if (DstIOpRec == nullptr)
+        return failedImport("EXTRACT_SUBREG operand #1 isn't a register class");
+
+      CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
+      CodeGenRegisterClass *SrcRC = CGRegs.getRegClass(
+          getInitValueAsRegClass(Dst->getChild(0)->getLeafValue()));
+
+      // It would be nice to leave this constraint implicit but we're required
+      // to pick a register class so constrain the result to a register class
+      // that can hold the correct MVT.
+      //
+      // FIXME: This may introduce an extra copy if the chosen class doesn't
+      //        actually contain the subregisters.
+      assert(Src->getExtTypes().size() == 1);
+
+      const auto &SrcRCDstRCPair =
+          SrcRC->getMatchingSubClassWithSubRegs(CGRegs, SubIdx);
+      assert(SrcRCDstRCPair->second && "Couldn't find a matching subclass");
+      M.addAction<ConstrainOperandToRegClassAction>("NewI", 0, *SrcRCDstRCPair->second);
+      M.addAction<ConstrainOperandToRegClassAction>("NewI", 1, *SrcRCDstRCPair->first);
+
+      // We're done with this pattern!  It's eligible for GISel emission; return
+      // it.
+      ++NumPatternImported;
+      return std::move(M);
+    }
+
+    return failedImport("EXTRACT_SUBREG child #1 is not a subreg index");
+  }
+
+  M.addAction<ConstrainOperandsToDefinitionAction>("NewI");
 
   // We're done with this pattern!  It's eligible for GISel emission; return it.
   ++NumPatternImported;