[PAC][AArch64] Lower ptrauth constants in code

This re-applies #94241 after fixing buildbot failure, see
https://lab.llvm.org/buildbot/#/builders/51/builds/570

According to standard, `constexpr` variables can be used in lambdas w/o
capturing - see https://en.cppreference.com/w/cpp/language/lambda.
However, MSVC used on buildkite seems to ignore that rule and does not
allow using uncaptured `constexpr` variables in lambdas: we have
"error C3493: 'Mask16' cannot be implicitly captured because no default
capture mode has been specified" - see
https://buildkite.com/llvm-project/github-pull-requests/builds/73238

Explicitly capturing a `constexpr` variable, however, makes buildbot
fail with "error: lambda capture 'Mask16' is not required to be captured
for this use [-Werror,-Wunused-lambda-capture]" - see
https://lab.llvm.org/buildbot/#/builders/51/builds/570.

Fix both cases by using `const` instead of `constexpr` and explicitly
capturing the variable.

Original PR description below.

Depends on #94240.

Define the following pseudos for lowering ptrauth constants in code:

- non-`extern_weak`:
  - no GOT load needed: `MOVaddrPAC` - similar to `MOVaddr`, with added
    PAC;
  - GOT load needed: `LOADgotPAC` - similar to `LOADgot`, with added PAC;
- `extern_weak`: `LOADauthptrstatic` - similar to `LOADgot`, but use a
  special stub slot named `sym$auth_ptr$key$disc` filled by dynamic linker
  during relocation resolving instead of a GOT slot.

---------

Co-authored-by: Ahmed Bougacha <[email protected]>

Author: kovdan01

llvm/docs/GlobalISel/GenericOpcode.rst

@@ -60,6 +60,17 @@ The address of a global value.
 
   %0(p0) = G_GLOBAL_VALUE @var_local
 
+G_PTRAUTH_GLOBAL_VALUE
+^^^^^^^^^^^^^^^^^^^^^^
+
+The signed address of a global value. Operands: address to be signed (pointer),
+key (32-bit imm), address for address discrimination (zero if not needed) and
+an extra discriminator (64-bit imm).
+
+.. code-block:: none
+
+  %0:_(p0) = G_PTRAUTH_GLOBAL_VALUE %1:_(p0), s32, %2:_(p0), s64
+
 G_BLOCK_ADDR
 ^^^^^^^^^^^^
 

llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h

@@ -886,6 +886,13 @@ class MachineIRBuilder {
   MachineInstrBuilder buildFConstant(const DstOp &Res, double Val);
   MachineInstrBuilder buildFConstant(const DstOp &Res, const APFloat &Val);
 
+  /// Build and insert G_PTRAUTH_GLOBAL_VALUE
+  ///
+  /// \return a MachineInstrBuilder for the newly created instruction.
+  MachineInstrBuilder buildConstantPtrAuth(const DstOp &Res,
+                                           const ConstantPtrAuth *CPA,
+                                           Register Addr, Register AddrDisc);
+
   /// Build and insert \p Res = COPY Op
   ///
   /// Register-to-register COPY sets \p Res to \p Op.

llvm/include/llvm/CodeGen/ISDOpcodes.h

@@ -83,6 +83,12 @@ enum NodeType {
   ExternalSymbol,
   BlockAddress,
 
+  /// A ptrauth constant.
+  /// ptr, key, addr-disc, disc
+  /// Note that the addr-disc can be a non-constant value, to allow representing
+  /// a constant global address signed using address-diversification, in code.
+  PtrAuthGlobalAddress,
+
   /// The address of the GOT
   GLOBAL_OFFSET_TABLE,
 

llvm/include/llvm/CodeGen/MachineModuleInfoImpls.h

@@ -61,10 +61,20 @@ class MachineModuleInfoMachO : public MachineModuleInfoImpl {
 /// MachineModuleInfoELF - This is a MachineModuleInfoImpl implementation
 /// for ELF targets.
 class MachineModuleInfoELF : public MachineModuleInfoImpl {
+public:
+  struct AuthStubInfo {
+    const MCExpr *AuthPtrRef;
+  };
+
+private:
   /// GVStubs - These stubs are used to materialize global addresses in PIC
   /// mode.
   DenseMap<MCSymbol *, StubValueTy> GVStubs;
 
+  /// AuthPtrStubs - These stubs are used to materialize signed addresses for
+  /// extern_weak symbols.
+  DenseMap<MCSymbol *, AuthStubInfo> AuthPtrStubs;
+
   virtual void anchor(); // Out of line virtual method.
 
 public:
@@ -75,9 +85,19 @@ class MachineModuleInfoELF : public MachineModuleInfoImpl {
     return GVStubs[Sym];
   }
 
+  AuthStubInfo &getAuthPtrStubEntry(MCSymbol *Sym) {
+    assert(Sym && "Key cannot be null");
+    return AuthPtrStubs[Sym];
+  }
+
   /// Accessor methods to return the set of stubs in sorted order.
 
   SymbolListTy GetGVStubList() { return getSortedStubs(GVStubs); }
+
+  using AuthStubPairTy = std::pair<MCSymbol *, AuthStubInfo>;
+  typedef std::vector<AuthStubPairTy> AuthStubListTy;
+
+  AuthStubListTy getAuthGVStubList();
 };
 
 /// MachineModuleInfoCOFF - This is a MachineModuleInfoImpl implementation

llvm/include/llvm/Support/TargetOpcodes.def

@@ -294,6 +294,9 @@ HANDLE_TARGET_OPCODE(G_FRAME_INDEX)
 /// Generic reference to global value.
 HANDLE_TARGET_OPCODE(G_GLOBAL_VALUE)
 
+/// Generic ptrauth-signed reference to global value.
+HANDLE_TARGET_OPCODE(G_PTRAUTH_GLOBAL_VALUE)
+
 /// Generic instruction to materialize the address of an object in the constant
 /// pool.
 HANDLE_TARGET_OPCODE(G_CONSTANT_POOL)

llvm/include/llvm/Target/GenericOpcodes.td

@@ -110,6 +110,12 @@ def G_GLOBAL_VALUE : GenericInstruction {
   let hasSideEffects = false;
 }
 
+def G_PTRAUTH_GLOBAL_VALUE : GenericInstruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins unknown:$addr, i32imm:$key, type1:$addrdisc, i64imm:$disc);
+  let hasSideEffects = 0;
+}
+
 def G_CONSTANT_POOL : GenericInstruction {
   let OutOperandList = (outs type0:$dst);
   let InOperandList = (ins unknown:$src);

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -3494,7 +3494,11 @@ bool IRTranslator::translate(const Constant &C, Register Reg) {
     EntryBuilder->buildConstant(Reg, 0);
   else if (auto GV = dyn_cast<GlobalValue>(&C))
     EntryBuilder->buildGlobalValue(Reg, GV);
-  else if (auto CAZ = dyn_cast<ConstantAggregateZero>(&C)) {
+  else if (auto CPA = dyn_cast<ConstantPtrAuth>(&C)) {
+    Register Addr = getOrCreateVReg(*CPA->getPointer());
+    Register AddrDisc = getOrCreateVReg(*CPA->getAddrDiscriminator());
+    EntryBuilder->buildConstantPtrAuth(Reg, CPA, Addr, AddrDisc);
+  } else if (auto CAZ = dyn_cast<ConstantAggregateZero>(&C)) {
     if (!isa<FixedVectorType>(CAZ->getType()))
       return false;
     // Return the scalar if it is a <1 x Ty> vector.

llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

@@ -397,6 +397,19 @@ MachineInstrBuilder MachineIRBuilder::buildFConstant(const DstOp &Res,
   return buildFConstant(Res, *CFP);
 }
 
+MachineInstrBuilder
+MachineIRBuilder::buildConstantPtrAuth(const DstOp &Res,
+                                       const ConstantPtrAuth *CPA,
+                                       Register Addr, Register AddrDisc) {
+  auto MIB = buildInstr(TargetOpcode::G_PTRAUTH_GLOBAL_VALUE);
+  Res.addDefToMIB(*getMRI(), MIB);
+  MIB.addUse(Addr);
+  MIB.addImm(CPA->getKey()->getZExtValue());
+  MIB.addUse(AddrDisc);
+  MIB.addImm(CPA->getDiscriminator()->getZExtValue());
+  return MIB;
+}
+
 MachineInstrBuilder MachineIRBuilder::buildBrCond(const SrcOp &Tst,
                                                   MachineBasicBlock &Dest) {
   assert(Tst.getLLTTy(*getMRI()).isScalar() && "invalid operand type");

llvm/lib/CodeGen/MachineModuleInfoImpls.cpp

@@ -13,6 +13,7 @@
 
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/MC/MCSymbol.h"
 
 using namespace llvm;
@@ -41,3 +42,25 @@ MachineModuleInfoImpl::SymbolListTy MachineModuleInfoImpl::getSortedStubs(
   Map.clear();
   return List;
 }
+
+template <typename MachineModuleInfoTarget>
+static typename MachineModuleInfoTarget::AuthStubListTy getAuthGVStubListHelper(
+    DenseMap<MCSymbol *, typename MachineModuleInfoTarget::AuthStubInfo>
+        &AuthPtrStubs) {
+  typename MachineModuleInfoTarget::AuthStubListTy List(AuthPtrStubs.begin(),
+                                                        AuthPtrStubs.end());
+
+  if (!List.empty())
+    llvm::sort(List.begin(), List.end(),
+               [](const typename MachineModuleInfoTarget::AuthStubPairTy &LHS,
+                  const typename MachineModuleInfoTarget::AuthStubPairTy &RHS) {
+                 return LHS.first->getName() < RHS.first->getName();
+               });
+
+  AuthPtrStubs.clear();
+  return List;
+}
+
+MachineModuleInfoELF::AuthStubListTy MachineModuleInfoELF::getAuthGVStubList() {
+  return getAuthGVStubListHelper<MachineModuleInfoELF>(AuthPtrStubs);
+}

llvm/lib/CodeGen/MachineVerifier.cpp

@@ -2066,6 +2066,12 @@ void MachineVerifier::verifyPreISelGenericInstruction(const MachineInstr *MI) {
       report("Dst operand 0 must be a pointer", MI);
     break;
   }
+  case TargetOpcode::G_PTRAUTH_GLOBAL_VALUE: {
+    const MachineOperand &AddrOp = MI->getOperand(1);
+    if (!AddrOp.isReg() || !MRI->getType(AddrOp.getReg()).isPointer())
+      report("addr operand must be a pointer", &AddrOp, 1);
+    break;
+  }
   default:
     break;
   }