[TableGen, CodeGen, CHERI] Add support for the cPTR wildcard value type. (#158426)

cPTR is a wildcard CHERI capability value type, used analogously to iPTR. This allows TableGen patterns to abstract over CHERI capability widths.

Co-authored-by: Jessica Clarke <jrtc27@jrtc27.com>

Author: resistor

llvm/include/llvm/CodeGen/ValueTypes.td

@@ -367,6 +367,10 @@ def aarch64mfp8 : ValueType<8,  253>;  // 8-bit value in FPR (AArch64)
 def c64 : VTCheriCapability<64, 254>;   // 64-bit CHERI capability value
 def c128 : VTCheriCapability<128, 255>; // 128-bit CHERI capability value
 
+// Pseudo valuetype mapped to the current CHERI capability pointer size.
+// Should only be used in TableGen.
+def cPTR : VTAny<503>;
+
 let isNormalValueType = false in {
 def token      : ValueType<0, 504>;  // TokenTy
 def MetadataVT : ValueType<0, 505> { // Metadata

llvm/include/llvm/CodeGenTypes/MachineValueType.h

@@ -582,6 +582,12 @@ namespace llvm {
                                 MVT::LAST_FP_SCALABLE_VECTOR_VALUETYPE,
                                 force_iteration_on_noniterable_enum);
     }
+
+    static auto cheri_capability_valuetypes() {
+      return enum_seq_inclusive(MVT::FIRST_CHERI_CAPABILITY_VALUETYPE,
+                                MVT::LAST_CHERI_CAPABILITY_VALUETYPE,
+                                force_iteration_on_noniterable_enum);
+    }
     /// @}
   };
 

llvm/test/TableGen/CPtrWildcard.td

@@ -0,0 +1,74 @@
+// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include %s -o - | FileCheck %s
+
+// Create an intrinsic that uses cPTR to overload on capability pointer types,
+// and verify that we can match it correct in SelectionDAG.
+
+// CHECK:        static const unsigned char MatcherTable[] = {
+// CHECK-NEXT: /*     0*/ OPC_CheckOpcode, TARGET_VAL(ISD::INTRINSIC_WO_CHAIN),
+// CHECK-NEXT:/*     3*/ OPC_CheckChild0Integer, 42,
+// CHECK-NEXT:/*     5*/ OPC_RecordChild1, // #0 = $src
+// CHECK-NEXT:/*     6*/ OPC_Scope, 9, /*->17*/ // 2 children in Scope
+// CHECK-NEXT:/*     8*/  OPC_CheckChild1Type, /*MVT::c64*/126|128,1/*254*/,
+// CHECK-NEXT:/*    11*/  OPC_MorphNodeTo1None, TARGET_VAL(MyTarget::C64_TO_I64),
+// CHECK-NEXT:                /*MVT::i64*/8, 1/*#Ops*/, 0,
+// CHECK-NEXT:            // Src: (intrinsic_wo_chain:{ *:[i64] } 21:{ *:[iPTR] }, c64:{ *:[c64] }:$src) - Complexity = 8
+// CHECK-NEXT:            // Dst: (C64_TO_I64:{ *:[i64] } ?:{ *:[c64] }:$src)
+// CHECK-NEXT:/*    17*/ /*Scope*/ 9, /*->27*/
+// CHECK-NEXT:/*    18*/  OPC_CheckChild1Type, /*MVT::c128*/127|128,1/*255*/,
+// CHECK-NEXT:/*    21*/  OPC_MorphNodeTo1None, TARGET_VAL(MyTarget::C128_TO_I64),
+// CHECK-NEXT:                /*MVT::i64*/8, 1/*#Ops*/, 0,
+// CHECK-NEXT:            // Src: (intrinsic_wo_chain:{ *:[i64] } 21:{ *:[iPTR] }, c128:{ *:[c128] }:$src) - Complexity = 8
+// CHECK-NEXT:            // Dst: (C128_TO_I64:{ *:[i64] } ?:{ *:[c128] }:$src)
+// CHECK-NEXT:/*    27*/ 0, /*End of Scope*/
+// CHECK-NEXT:    0
+// CHECK-NEXT:  }; // Total Array size is 29 bytes
+
+include "llvm/Target/Target.td"
+
+def my_cap_ty : LLVMQualPointerType<200> {
+  let VT = cPTR;
+}
+
+def int_cap_get_length :
+  Intrinsic<[llvm_i64_ty],
+            [my_cap_ty],
+            [IntrNoMem, IntrWillReturn]>;
+
+class CapReg<string n> : Register<n> {
+    let Namespace = "MyTarget";
+}
+
+def C64  : CapReg<"c0">;
+def C64s
+    : RegisterClass<"MyTarget", [i64, c64], 64,
+                    (add C64)>;
+
+def C128  : CapReg<"c0">;
+def C128s
+    : RegisterClass<"MyTarget", [c128], 64,
+                    (add C128)>;
+
+def C64_TO_I64 : Instruction {
+  let Namespace = "MyTarget";
+  let OutOperandList = (outs C64s:$dst);
+  let InOperandList = (ins C64s:$src);
+}
+
+def C128_TO_I64 : Instruction {
+  let Namespace = "MyTarget";
+  let OutOperandList = (outs C64s:$dst);
+  let InOperandList = (ins C128s:$src);
+}
+
+def : Pat<
+  (int_cap_get_length c64:$src),
+  (C64_TO_I64 $src)
+>;
+
+def : Pat<
+  (int_cap_get_length c128:$src),
+  (C128_TO_I64 $src)
+>;
+
+def MyTargetISA : InstrInfo;
+def MyTarget : Target { let InstructionSet = MyTargetISA; }

llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp

@@ -335,6 +335,8 @@ bool TypeSetByHwMode::intersect(SetType &Out, const SetType &In) {
   using WildPartT = std::pair<MVT, std::function<bool(MVT)>>;
   static const WildPartT WildParts[] = {
       {MVT::iPTR, [](MVT T) { return T.isScalarInteger() || T == MVT::iPTR; }},
+      {MVT::cPTR,
+       [](MVT T) { return T.isCheriCapability() || T == MVT::cPTR; }},
   };
 
   bool Changed = false;
@@ -816,6 +818,10 @@ void TypeInfer::expandOverloads(TypeSetByHwMode::SetType &Out,
   if (Out.count(MVT::pAny)) {
     Out.erase(MVT::pAny);
     Out.insert(MVT::iPTR);
+    for (MVT T : MVT::cheri_capability_valuetypes()) {
+      if (Legal.count(T))
+        Out.insert(MVT::cPTR);
+    }
   } else if (Out.count(MVT::iAny)) {
     Out.erase(MVT::iAny);
     for (MVT T : MVT::integer_valuetypes())
@@ -1647,9 +1653,11 @@ bool SDTypeConstraint::ApplyTypeConstraint(TreePatternNode &N,
   case SDTCisVT:
     // Operand must be a particular type.
     return NodeToApply.UpdateNodeType(ResNo, VVT, TP);
-  case SDTCisPtrTy:
-    // Operand must be same as target pointer type.
-    return NodeToApply.UpdateNodeType(ResNo, MVT::iPTR, TP);
+  case SDTCisPtrTy: {
+    // Operand must be a legal pointer (iPTR, or possibly cPTR) type.
+    const TypeSetByHwMode &PtrTys = TP.getDAGPatterns().getLegalPtrTypes();
+    return NodeToApply.UpdateNodeType(ResNo, PtrTys, TP);
+  }
   case SDTCisInt:
     // Require it to be one of the legal integer VTs.
     return TI.EnforceInteger(NodeToApply.getExtType(ResNo));
@@ -3293,6 +3301,7 @@ CodeGenDAGPatterns::CodeGenDAGPatterns(const RecordKeeper &R,
                                        PatternRewriterFn PatternRewriter)
     : Records(R), Target(R), Intrinsics(R),
       LegalVTS(Target.getLegalValueTypes()),
+      LegalPtrVTS(ComputeLegalPtrTypes()),
       PatternRewriter(std::move(PatternRewriter)) {
   ParseNodeInfo();
   ParseNodeTransforms();
@@ -3328,6 +3337,36 @@ const Record *CodeGenDAGPatterns::getSDNodeNamed(StringRef Name) const {
   return N;
 }
 
+// Compute the subset of iPTR and cPTR legal for each mode, coalescing into the
+// default mode where possible to avoid predicate explosion.
+TypeSetByHwMode CodeGenDAGPatterns::ComputeLegalPtrTypes() const {
+  auto LegalPtrsForSet = [](const MachineValueTypeSet &In) {
+    MachineValueTypeSet Out;
+    Out.insert(MVT::iPTR);
+    for (MVT T : MVT::cheri_capability_valuetypes()) {
+      if (In.count(T)) {
+        Out.insert(MVT::cPTR);
+        break;
+      }
+    }
+    return Out;
+  };
+
+  const TypeSetByHwMode &LegalTypes = getLegalTypes();
+  MachineValueTypeSet LegalPtrsDefault =
+      LegalPtrsForSet(LegalTypes.get(DefaultMode));
+
+  TypeSetByHwMode LegalPtrTypes;
+  for (const auto &I : LegalTypes) {
+    MachineValueTypeSet S = LegalPtrsForSet(I.second);
+    if (I.first != DefaultMode && S == LegalPtrsDefault)
+      continue;
+    LegalPtrTypes.getOrCreate(I.first).insert(S);
+  }
+
+  return LegalPtrTypes;
+}
+
 // Parse all of the SDNode definitions for the target, populating SDNodes.
 void CodeGenDAGPatterns::ParseNodeInfo() {
   const CodeGenHwModes &CGH = getTargetInfo().getHwModes();

llvm/utils/TableGen/Common/CodeGenDAGPatterns.h

@@ -1135,6 +1135,7 @@ class CodeGenDAGPatterns {
   std::vector<PatternToMatch> PatternsToMatch;
 
   TypeSetByHwMode LegalVTS;
+  TypeSetByHwMode LegalPtrVTS;
 
   using PatternRewriterFn = std::function<void(TreePattern *)>;
   PatternRewriterFn PatternRewriter;
@@ -1148,6 +1149,7 @@ class CodeGenDAGPatterns {
   CodeGenTarget &getTargetInfo() { return Target; }
   const CodeGenTarget &getTargetInfo() const { return Target; }
   const TypeSetByHwMode &getLegalTypes() const { return LegalVTS; }
+  const TypeSetByHwMode &getLegalPtrTypes() const { return LegalPtrVTS; }
 
   const Record *getSDNodeNamed(StringRef Name) const;
 
@@ -1249,6 +1251,7 @@ class CodeGenDAGPatterns {
   }
 
 private:
+  TypeSetByHwMode ComputeLegalPtrTypes() const;
   void ParseNodeInfo();
   void ParseNodeTransforms();
   void ParseComplexPatterns();

llvm/utils/TableGen/Common/DAGISelMatcher.cpp

@@ -328,6 +328,14 @@ static bool TypesAreContradictory(MVT::SimpleValueType T1,
   if (T1 == T2)
     return false;
 
+  if (T1 == MVT::pAny)
+    return TypesAreContradictory(MVT::iPTR, T2) &&
+           TypesAreContradictory(MVT::cPTR, T2);
+
+  if (T2 == MVT::pAny)
+    return TypesAreContradictory(T1, MVT::iPTR) &&
+           TypesAreContradictory(T1, MVT::cPTR);
+
   // If either type is about iPtr, then they don't conflict unless the other
   // one is not a scalar integer type.
   if (T1 == MVT::iPTR)
@@ -336,7 +344,13 @@ static bool TypesAreContradictory(MVT::SimpleValueType T1,
   if (T2 == MVT::iPTR)
     return !MVT(T1).isInteger() || MVT(T1).isVector();
 
-  // Otherwise, they are two different non-iPTR types, they conflict.
+  if (T1 == MVT::cPTR)
+    return !MVT(T2).isCheriCapability() || MVT(T2).isVector();
+
+  if (T2 == MVT::cPTR)
+    return !MVT(T1).isCheriCapability() || MVT(T1).isVector();
+
+  // Otherwise, they are two different non-iPTR/cPTR types, they conflict.
   return true;
 }
 

llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.cpp

@@ -1467,7 +1467,9 @@ Error OperandMatcher::addTypeCheckPredicate(const TypeSetByHwMode &VTy,
   if (!VTy.isMachineValueType())
     return failUnsupported("unsupported typeset");
 
-  if (VTy.getMachineValueType() == MVT::iPTR && OperandIsAPointer) {
+  if ((VTy.getMachineValueType() == MVT::iPTR ||
+       VTy.getMachineValueType() == MVT::cPTR) &&
+      OperandIsAPointer) {
     addPredicate<PointerToAnyOperandMatcher>(0);
     return Error::success();
   }

llvm/utils/TableGen/DAGISelMatcherOpt.cpp

@@ -519,9 +519,9 @@ static void FactorScope(std::unique_ptr<Matcher> &MatcherPtr) {
       CheckTypeMatcher *CTM = cast_or_null<CheckTypeMatcher>(
           FindNodeWithKind(Optn, Matcher::CheckType));
       if (!CTM ||
-          // iPTR checks could alias any other case without us knowing, don't
-          // bother with them.
-          CTM->getType() == MVT::iPTR ||
+          // iPTR/cPTR checks could alias any other case without us knowing,
+          // don't bother with them.
+          CTM->getType() == MVT::iPTR || CTM->getType() == MVT::cPTR ||
           // SwitchType only works for result #0.
           CTM->getResNo() != 0 ||
           // If the CheckType isn't at the start of the list, see if we can move