[Target][RISCV] Add HwMode support to subregister index size/offset. (#86368)

This is needed to provide proper size and offset for the GPRPair subreg
indices on RISC-V. The size of a GPR already uses HwMode. Previously we
said the subreg indices have unknown size and offset, but this stops
DwarfExpression::addMachineReg from being able to find the registers
that make up the pair.

I believe this fixes llvm/llvm-project#85864
but need to verify.

Author: topperc

llvm/include/llvm/Target/Target.td

@@ -83,10 +83,27 @@ class RegInfoByHwMode<list<HwMode> Ms = [], list<RegInfo> Ts = []>
   list<RegInfo> Objects = Ts;
 }
 
+class SubRegRange<int size, int offset = 0> {
+  int Size = size;      // Sub register size in bits.
+  int Offset = offset;  // Offset of the first bit of the sub-reg index.
+}
+
+class SubRegRangeByHwMode<list<HwMode> Ms = [], list<SubRegRange> Ts = []>
+    : HwModeSelect<Ms> {
+  // The length of this list must be the same as the length of Ms.
+  list<SubRegRange> Objects = Ts;
+}
+
 // SubRegIndex - Use instances of SubRegIndex to identify subregisters.
 class SubRegIndex<int size, int offset = 0> {
   string Namespace = "";
 
+  // The size/offset information, parameterized by a HW mode.
+  // If the HwModes provided for SubRegRanges does not include the DefaultMode,
+  // the/ Size and Offset fields below will be used for the default. Otherwise,
+  // the Size and Offset fields are ignored.
+  SubRegRangeByHwMode SubRegRanges;
+
   // Size - Size (in bits) of the sub-registers represented by this index.
   int Size = size;
 

llvm/lib/CodeGen/TargetRegisterInfo.cpp

@@ -595,13 +595,13 @@ bool TargetRegisterInfo::getCoveringSubRegIndexes(
 unsigned TargetRegisterInfo::getSubRegIdxSize(unsigned Idx) const {
   assert(Idx && Idx < getNumSubRegIndices() &&
          "This is not a subregister index");
-  return SubRegIdxRanges[Idx].Size;
+  return SubRegIdxRanges[HwMode * getNumSubRegIndices() + Idx].Size;
 }
 
 unsigned TargetRegisterInfo::getSubRegIdxOffset(unsigned Idx) const {
   assert(Idx && Idx < getNumSubRegIndices() &&
          "This is not a subregister index");
-  return SubRegIdxRanges[Idx].Offset;
+  return SubRegIdxRanges[HwMode * getNumSubRegIndices() + Idx].Offset;
 }
 
 Register

llvm/lib/Target/RISCV/RISCVRegisterInfo.td

@@ -64,9 +64,14 @@ def sub_vrm1_6 : ComposedSubRegIndex<sub_vrm2_3, sub_vrm1_0>;
 def sub_vrm1_7 : ComposedSubRegIndex<sub_vrm2_3, sub_vrm1_1>;
 
 // GPR sizes change with HwMode.
-// FIXME: Support HwMode in SubRegIndex?
-def sub_gpr_even : SubRegIndex<-1>;
-def sub_gpr_odd  : SubRegIndex<-1, -1>;
+def sub_gpr_even : SubRegIndex<32> {
+  let SubRegRanges = SubRegRangeByHwMode<[RV32, RV64],
+                                         [SubRegRange<32>, SubRegRange<64>]>;
+}
+def sub_gpr_odd  : SubRegIndex<32, 32> {
+  let SubRegRanges = SubRegRangeByHwMode<[RV32, RV64],
+                                         [SubRegRange<32, 32>, SubRegRange<64, 64>]>;
+}
 } // Namespace = "RISCV"
 
 // Integer registers

llvm/test/TableGen/ConcatenatedSubregs.td

@@ -90,16 +90,19 @@ def TestTarget : Target;
 // CHECK-LABEL: RegisterClass DRegs:
 
 // CHECK-LABEL: SubRegIndex ssub1:
-// CHECK:        Offset, Size: 16, 16
+// CHECK:        Offset: { Default:16 }
+// CHECK:        Size: { Default:16 }
 // CHECK-LABEL: SubRegIndex sub0:
 // CHECK-LABEL: SubRegIndex sub1:
 // CHECK-LABEL: SubRegIndex sub2:
 // Check inferred indexes:
 // CHECK-LABEL: SubRegIndex ssub1_ssub2:
-// CHECK:         Offset, Size: 16, 65535
+// CHECK:         Offset: { Default:16 }
+// CHECK:         Size: { Default:65535 }
 // CHECK-LABEL: SubRegIndex ssub3_ssub4:
 // CHECK-LABEL: SubRegIndex ssub0_ssub1_ssub2_ssub3:
-// CHECK:         Offset, Size: 65535, 65535
+// CHECK:         Offset: { Default:65535 }
+// CHECK:         Size: { Default:65535 }
 // CHECK-LABEL: SubRegIndex ssub1_ssub2_ssub3_ssub4:
 
 // Check that all subregs are generated on some examples

llvm/test/TableGen/HwModeSubRegs.td

@@ -0,0 +1,75 @@
+// RUN: llvm-tblgen -gen-register-info -register-info-debug -I %p/../../include %s -o /dev/null 2>&1 | FileCheck %s
+include "llvm/Target/Target.td"
+
+def HasFeat : Predicate<"Subtarget->hasFeat()">;
+
+def TestMode : HwMode<"+feat1", [HasFeat]>;
+
+class MyReg<string n>
+  : Register<n> {
+  let Namespace = "Test";
+}
+class MyClass<int size, list<ValueType> types, dag registers>
+  : RegisterClass<"Test", types, size, registers> {
+  let Size = size;
+}
+
+def X0 : MyReg<"x0">;
+def X1 : MyReg<"x1">;
+def X2 : MyReg<"x2">;
+def X3 : MyReg<"x3">;
+def X4 : MyReg<"x4">;
+def X5 : MyReg<"x5">;
+def X6 : MyReg<"x6">;
+def X7 : MyReg<"x7">;
+def X8 : MyReg<"x8">;
+def X9 : MyReg<"x9">;
+def X10 : MyReg<"x10">;
+def X11 : MyReg<"x11">;
+def X12 : MyReg<"x12">;
+def X13 : MyReg<"x13">;
+def X14 : MyReg<"x14">;
+def X15 : MyReg<"x15">;
+
+def ModeVT : ValueTypeByHwMode<[DefaultMode, TestMode],
+                               [i32,  i64]>;
+let RegInfos = RegInfoByHwMode<[DefaultMode, TestMode],
+                               [RegInfo<32,32,32>, RegInfo<64,64,64>]> in
+def XRegs : MyClass<32, [ModeVT], (sequence "X%u", 0, 15)>;
+
+def sub_even : SubRegIndex<32> {
+  let SubRegRanges = SubRegRangeByHwMode<[DefaultMode, TestMode],
+                                         [SubRegRange<32>, SubRegRange<64>]>;
+}
+def sub_odd  : SubRegIndex<32, 32> {
+  let SubRegRanges = SubRegRangeByHwMode<[DefaultMode, TestMode],
+                                         [SubRegRange<32, 32>, SubRegRange<64, 64>]>;
+}
+
+def XPairs : RegisterTuples<[sub_even, sub_odd],
+                            [(decimate (rotl XRegs, 0), 2),
+                             (decimate (rotl XRegs, 1), 2)]>;
+
+let RegInfos = RegInfoByHwMode<[DefaultMode, TestMode],
+                               [RegInfo<64,64,32>, RegInfo<128,128,64>]> in
+def XPairsClass : MyClass<64, [untyped], (add XPairs)>;
+
+def TestTarget : Target;
+
+// CHECK-LABEL: RegisterClass XRegs:
+// CHECK: SpillSize: { Default:32 TestMode:64 }
+// CHECK: SpillAlignment: { Default:32 TestMode:64 }
+// CHECK: Regs: X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15
+
+// CHECK-LABEL: RegisterClass XPairsClass:
+// CHECK: SpillSize: { Default:64 TestMode:128 }
+// CHECK: SpillAlignment: { Default:32 TestMode:64 }
+// CHECK: CoveredBySubRegs: 1
+// CHECK: Regs: X0_X1 X2_X3 X4_X5 X6_X7 X8_X9 X10_X11 X12_X13 X14_X15
+
+// CHECK-LABEL: SubRegIndex sub_even:
+// CHECK: Offset: { Default:0 TestMode:0 }
+// CHECK: Size: { Default:32 TestMode:64 }
+// CHECK-LABEL: SubRegIndex sub_odd:
+// CHECK: Offset: { Default:32 TestMode:64 }
+// CHECK: Size: { Default:32 TestMode:64 }

llvm/utils/TableGen/Common/CodeGenRegisters.cpp

@@ -47,19 +47,24 @@ using namespace llvm;
 //                             CodeGenSubRegIndex
 //===----------------------------------------------------------------------===//
 
-CodeGenSubRegIndex::CodeGenSubRegIndex(Record *R, unsigned Enum)
+CodeGenSubRegIndex::CodeGenSubRegIndex(Record *R, unsigned Enum,
+                                       const CodeGenHwModes &CGH)
     : TheDef(R), EnumValue(Enum), AllSuperRegsCovered(true), Artificial(true) {
   Name = std::string(R->getName());
   if (R->getValue("Namespace"))
     Namespace = std::string(R->getValueAsString("Namespace"));
-  Size = R->getValueAsInt("Size");
-  Offset = R->getValueAsInt("Offset");
+
+  if (const RecordVal *RV = R->getValue("SubRegRanges"))
+    if (auto *DI = dyn_cast_or_null<DefInit>(RV->getValue()))
+      Range = SubRegRangeByHwMode(DI->getDef(), CGH);
+  if (!Range.hasDefault())
+    Range.insertSubRegRangeForMode(DefaultMode, SubRegRange(R));
 }
 
 CodeGenSubRegIndex::CodeGenSubRegIndex(StringRef N, StringRef Nspace,
                                        unsigned Enum)
     : TheDef(nullptr), Name(std::string(N)), Namespace(std::string(Nspace)),
-      Size(-1), Offset(-1), EnumValue(Enum), AllSuperRegsCovered(true),
+      Range(SubRegRange(-1, -1)), EnumValue(Enum), AllSuperRegsCovered(true),
       Artificial(true) {}
 
 std::string CodeGenSubRegIndex::getQualifiedName() const {
@@ -81,7 +86,7 @@ void CodeGenSubRegIndex::updateComponents(CodeGenRegBank &RegBank) {
                       "ComposedOf must have exactly two entries");
     CodeGenSubRegIndex *A = RegBank.getSubRegIdx(Comps[0]);
     CodeGenSubRegIndex *B = RegBank.getSubRegIdx(Comps[1]);
-    CodeGenSubRegIndex *X = A->addComposite(B, this);
+    CodeGenSubRegIndex *X = A->addComposite(B, this, RegBank.getHwModes());
     if (X)
       PrintFatalError(TheDef->getLoc(), "Ambiguous ComposedOf entries");
   }
@@ -518,7 +523,8 @@ void CodeGenRegister::computeSecondarySubRegs(CodeGenRegBank &RegBank) {
 
       // Each part of Cand is a sub-register of this. Make the full Cand also
       // a sub-register with a concatenated sub-register index.
-      CodeGenSubRegIndex *Concat = RegBank.getConcatSubRegIndex(Parts);
+      CodeGenSubRegIndex *Concat =
+          RegBank.getConcatSubRegIndex(Parts, RegBank.getHwModes());
       std::pair<CodeGenSubRegIndex *, CodeGenRegister *> NewSubReg =
           std::pair(Concat, Cand);
 
@@ -542,7 +548,7 @@ void CodeGenRegister::computeSecondarySubRegs(CodeGenRegBank &RegBank) {
         PrintFatalError(TheDef->getLoc(), "No SubRegIndex for " +
                                               SubReg.second->getName() +
                                               " in " + getName());
-      NewIdx->addComposite(SubReg.first, SubIdx);
+      NewIdx->addComposite(SubReg.first, SubIdx, RegBank.getHwModes());
     }
   }
 }
@@ -1315,7 +1321,7 @@ CodeGenSubRegIndex *CodeGenRegBank::getSubRegIdx(Record *Def) {
   CodeGenSubRegIndex *&Idx = Def2SubRegIdx[Def];
   if (Idx)
     return Idx;
-  SubRegIndices.emplace_back(Def, SubRegIndices.size() + 1);
+  SubRegIndices.emplace_back(Def, SubRegIndices.size() + 1, getHwModes());
   Idx = &SubRegIndices.back();
   return Idx;
 }
@@ -1379,12 +1385,13 @@ CodeGenRegBank::getCompositeSubRegIndex(CodeGenSubRegIndex *A,
   // None exists, synthesize one.
   std::string Name = A->getName() + "_then_" + B->getName();
   Comp = createSubRegIndex(Name, A->getNamespace());
-  A->addComposite(B, Comp);
+  A->addComposite(B, Comp, getHwModes());
   return Comp;
 }
 
 CodeGenSubRegIndex *CodeGenRegBank::getConcatSubRegIndex(
-    const SmallVector<CodeGenSubRegIndex *, 8> &Parts) {
+    const SmallVector<CodeGenSubRegIndex *, 8> &Parts,
+    const CodeGenHwModes &CGH) {
   assert(Parts.size() > 1 && "Need two parts to concatenate");
 #ifndef NDEBUG
   for (CodeGenSubRegIndex *Idx : Parts) {
@@ -1399,28 +1406,47 @@ CodeGenSubRegIndex *CodeGenRegBank::getConcatSubRegIndex(
 
   // None exists, synthesize one.
   std::string Name = Parts.front()->getName();
-  // Determine whether all parts are contiguous.
-  bool IsContinuous = true;
-  unsigned Size = Parts.front()->Size;
-  unsigned LastOffset = Parts.front()->Offset;
-  unsigned LastSize = Parts.front()->Size;
   const unsigned UnknownSize = (uint16_t)-1;
+
   for (unsigned i = 1, e = Parts.size(); i != e; ++i) {
     Name += '_';
     Name += Parts[i]->getName();
-    if (Size == UnknownSize || Parts[i]->Size == UnknownSize)
-      Size = UnknownSize;
-    else
-      Size += Parts[i]->Size;
-    if (LastSize == UnknownSize || Parts[i]->Offset != (LastOffset + LastSize))
-      IsContinuous = false;
-    LastOffset = Parts[i]->Offset;
-    LastSize = Parts[i]->Size;
   }
+
   Idx = createSubRegIndex(Name, Parts.front()->getNamespace());
-  Idx->Size = Size;
-  Idx->Offset = IsContinuous ? Parts.front()->Offset : -1;
   Idx->ConcatenationOf.assign(Parts.begin(), Parts.end());
+
+  unsigned NumModes = CGH.getNumModeIds();
+  for (unsigned M = 0; M < NumModes; ++M) {
+    const CodeGenSubRegIndex *Part = Parts.front();
+
+    // Determine whether all parts are contiguous.
+    bool IsContinuous = true;
+    const SubRegRange &FirstPartRange = Part->Range.get(M);
+    unsigned Size = FirstPartRange.Size;
+    unsigned LastOffset = FirstPartRange.Offset;
+    unsigned LastSize = FirstPartRange.Size;
+
+    for (unsigned i = 1, e = Parts.size(); i != e; ++i) {
+      Part = Parts[i];
+      Name += '_';
+      Name += Part->getName();
+
+      const SubRegRange &PartRange = Part->Range.get(M);
+      if (Size == UnknownSize || PartRange.Size == UnknownSize)
+        Size = UnknownSize;
+      else
+        Size += PartRange.Size;
+      if (LastSize == UnknownSize ||
+          PartRange.Offset != (LastOffset + LastSize))
+        IsContinuous = false;
+      LastOffset = PartRange.Offset;
+      LastSize = PartRange.Size;
+    }
+    unsigned Offset = IsContinuous ? FirstPartRange.Offset : -1;
+    Idx->Range.get(M) = SubRegRange(Size, Offset);
+  }
+
   return Idx;
 }
 
@@ -1504,7 +1530,8 @@ void CodeGenRegBank::computeComposites() {
         assert(Idx3 && "Sub-register doesn't have an index");
 
         // Conflicting composition? Emit a warning but allow it.
-        if (CodeGenSubRegIndex *Prev = Idx1->addComposite(Idx2, Idx3)) {
+        if (CodeGenSubRegIndex *Prev =
+                Idx1->addComposite(Idx2, Idx3, getHwModes())) {
           // If the composition was not user-defined, always emit a warning.
           if (!UserDefined.count({Idx1, Idx2}) ||
               agree(compose(Idx1, Idx2), SubRegAction.at(Idx3)))

llvm/utils/TableGen/Common/CodeGenRegisters.h

@@ -68,8 +68,7 @@ class CodeGenSubRegIndex {
   std::string Namespace;
 
 public:
-  uint16_t Size;
-  uint16_t Offset;
+  SubRegRangeByHwMode Range;
   const unsigned EnumValue;
   mutable LaneBitmask LaneMask;
   mutable SmallVector<MaskRolPair, 1> CompositionLaneMaskTransform;
@@ -86,7 +85,7 @@ class CodeGenSubRegIndex {
   // indexes are not used to create new register classes.
   bool Artificial;
 
-  CodeGenSubRegIndex(Record *R, unsigned Enum);
+  CodeGenSubRegIndex(Record *R, unsigned Enum, const CodeGenHwModes &CGH);
   CodeGenSubRegIndex(StringRef N, StringRef Nspace, unsigned Enum);
   CodeGenSubRegIndex(CodeGenSubRegIndex &) = delete;
 
@@ -108,19 +107,42 @@ class CodeGenSubRegIndex {
 
   // Add a composite subreg index: this+A = B.
   // Return a conflicting composite, or NULL
-  CodeGenSubRegIndex *addComposite(CodeGenSubRegIndex *A,
-                                   CodeGenSubRegIndex *B) {
+  CodeGenSubRegIndex *addComposite(CodeGenSubRegIndex *A, CodeGenSubRegIndex *B,
+                                   const CodeGenHwModes &CGH) {
     assert(A && B);
     std::pair<CompMap::iterator, bool> Ins = Composed.insert(std::pair(A, B));
+
     // Synthetic subreg indices that aren't contiguous (for instance ARM
     // register tuples) don't have a bit range, so it's OK to let
     // B->Offset == -1. For the other cases, accumulate the offset and set
     // the size here. Only do so if there is no offset yet though.
-    if ((Offset != (uint16_t)-1 && A->Offset != (uint16_t)-1) &&
-        (B->Offset == (uint16_t)-1)) {
-      B->Offset = Offset + A->Offset;
-      B->Size = A->Size;
+    unsigned NumModes = CGH.getNumModeIds();
+    // Skip default mode.
+    for (unsigned M = 0; M < NumModes; ++M) {
+      // Handle DefaultMode last.
+      if (M == DefaultMode)
+        continue;
+      SubRegRange &Range = this->Range.get(M);
+      SubRegRange &ARange = A->Range.get(M);
+      SubRegRange &BRange = B->Range.get(M);
+
+      if (Range.Offset != (uint16_t)-1 && ARange.Offset != (uint16_t)-1 &&
+          BRange.Offset == (uint16_t)-1) {
+        BRange.Offset = Range.Offset + ARange.Offset;
+        BRange.Size = ARange.Size;
+      }
+    }
+
+    // Now handle default.
+    SubRegRange &Range = this->Range.get(DefaultMode);
+    SubRegRange &ARange = A->Range.get(DefaultMode);
+    SubRegRange &BRange = B->Range.get(DefaultMode);
+    if (Range.Offset != (uint16_t)-1 && ARange.Offset != (uint16_t)-1 &&
+        BRange.Offset == (uint16_t)-1) {
+      BRange.Offset = Range.Offset + ARange.Offset;
+      BRange.Size = ARange.Size;
     }
+
     return (Ins.second || Ins.first->second == B) ? nullptr : Ins.first->second;
   }
 
@@ -681,7 +703,8 @@ class CodeGenRegBank {
   // Find or create a sub-register index representing the concatenation of
   // non-overlapping sibling indices.
   CodeGenSubRegIndex *
-  getConcatSubRegIndex(const SmallVector<CodeGenSubRegIndex *, 8> &);
+  getConcatSubRegIndex(const SmallVector<CodeGenSubRegIndex *, 8> &,
+                       const CodeGenHwModes &CGH);
 
   const std::deque<CodeGenRegister> &getRegisters() const { return Registers; }