Add signed access enforcement to begin_access

This will be used for supporting imported c function pointers with custom __ptrauth qualifier.

Author: meg-gupta

docs/SIL.rst

@@ -4522,6 +4522,7 @@ begin_access
   sil-enforcement ::= static
   sil-enforcement ::= dynamic
   sil-enforcement ::= unsafe
+  sil-enforcement ::= signed
   %1 = begin_access [read] [unknown] %0 : $*T
   // %0 must be of $*T type.
 
@@ -4564,6 +4565,9 @@ runtime for the duration of its scope. This access may still conflict with an
 outer access scope; therefore may still require dynamic enforcement at a single
 point.
 
+A ``signed`` access is for pointers that are signed in architectures that support
+pointer signing.
+
 A ``builtin`` access was emitted for a user-controlled Builtin (e.g. the
 standard library's KeyPath access). Non-builtin accesses are auto-generated by
 the compiler to enforce formal access that derives from the language. A

include/swift/SIL/SILInstruction.h

@@ -4418,8 +4418,13 @@ enum class SILAccessEnforcement : uint8_t {
   /// behavior.
   Unsafe,
 
+  /// Access to pointers that are signed via pointer authentication mechanishm.
+  /// Such pointers should be authenticated before read and signed before a
+  /// write. Optimizer should avoid promoting such accesses to values.
+  Signed,
+
   // This enum is encoded.
-  Last = Unsafe
+  Last = Signed
 };
 StringRef getSILAccessEnforcementName(SILAccessEnforcement enforcement);
 
@@ -4492,9 +4497,9 @@ class BeginAccessInst
       : BeginAccessBase(loc, accessKind, enforcement, noNestedConflict,
         fromBuiltin, lvalue, lvalue->getType()) {
 
-    static_assert(unsigned(SILAccessKind::Last) < (1 << 2),
+    static_assert(unsigned(SILAccessKind::Last) < (1 << 3),
                   "reserve sufficient bits for serialized SIL");
-    static_assert(unsigned(SILAccessEnforcement::Last) < (1 << 2),
+    static_assert(unsigned(SILAccessEnforcement::Last) < (1 << 3),
                   "reserve sufficient bits for serialized SIL");
 
     static_assert(unsigned(SILAccessKind::Last) <

include/swift/SIL/SILNode.h

@@ -122,7 +122,7 @@ class alignas(8) SILNode :
   enum { NumAssignOwnershipQualifierBits = 2 };
   enum { NumAssignByWrapperModeBits = 2 };
   enum { NumSILAccessKindBits = 2 };
-  enum { NumSILAccessEnforcementBits = 2 };
+  enum { NumSILAccessEnforcementBits = 3 };
   enum { NumAllocRefTailTypesBits = 4 };
 
 protected:

lib/IRGen/IRGenSIL.cpp

@@ -5750,6 +5750,7 @@ void IRGenSILFunction::visitBeginAccessInst(BeginAccessInst *access) {
 
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     // nothing to do
     setLoweredAddress(access, addr);
     return;
@@ -5790,6 +5791,7 @@ void IRGenSILFunction::visitBeginUnpairedAccessInst(
 
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     // nothing to do
     return;
 
@@ -5835,6 +5837,7 @@ void IRGenSILFunction::visitEndAccessInst(EndAccessInst *i) {
 
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     // nothing to do
     return;
 
@@ -5862,6 +5865,7 @@ void IRGenSILFunction::visitEndUnpairedAccessInst(EndUnpairedAccessInst *i) {
 
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     // nothing to do
     return;
 

lib/SIL/IR/SILInstructions.cpp

@@ -1206,6 +1206,8 @@ StringRef swift::getSILAccessEnforcementName(SILAccessEnforcement enforcement) {
   case SILAccessEnforcement::Static: return "static";
   case SILAccessEnforcement::Dynamic: return "dynamic";
   case SILAccessEnforcement::Unsafe: return "unsafe";
+  case SILAccessEnforcement::Signed:
+    return "signed";
   }
   llvm_unreachable("bad access enforcement");
 }

lib/SIL/Parser/ParseSIL.cpp

@@ -4326,6 +4326,8 @@ bool SILParser::parseSpecificSILInstruction(SILBuilder &B,
         setEnforcement(SILAccessEnforcement::Dynamic);
       } else if (attr == "unsafe") {
         setEnforcement(SILAccessEnforcement::Unsafe);
+      } else if (attr == "signed") {
+        setEnforcement(SILAccessEnforcement::Signed);
       } else if (attr == "init") {
         setKind(SILAccessKind::Init);
       } else if (attr == "read") {

lib/SILOptimizer/Mandatory/AccessMarkerElimination.cpp

@@ -77,6 +77,7 @@ bool AccessMarkerElimination::shouldPreserveAccess(
   switch (enforcement) {
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     return false;
   case SILAccessEnforcement::Unknown:
   case SILAccessEnforcement::Dynamic:

lib/SILOptimizer/Utils/SILInliner.cpp

@@ -770,6 +770,7 @@ static InlineCost getEnforcementCost(SILAccessEnforcement enforcement) {
     return InlineCost::Expensive;
   case SILAccessEnforcement::Static:
   case SILAccessEnforcement::Unsafe:
+  case SILAccessEnforcement::Signed:
     return InlineCost::Free;
   }
   llvm_unreachable("bad enforcement");