Feature: Platform.PreservedRegisters

Added support for explictly stating which registers are _not_ modified after a procedure call. Added support for extended C keywords for MacOS (may need refinement to match the actual keywords used in MPW C)
gitmesam · Apr 24, 2023 · d838eba · d838eba
1 parent 3c67e6c
commit d838eba
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Showing 15 changed files with 92 additions and 14 deletions.
diff --git a/src/Core/Configuration/PlatformArchitectureDefinition.cs b/src/Core/Configuration/PlatformArchitectureDefinition.cs
@@ -34,12 +34,14 @@ public class PlatformArchitectureDefinition
         public PlatformArchitectureDefinition()
         {
             this.TrashedRegisters = new List<string>();
+            this.PreservedRegisters = new List<string>();
             this.TypeLibraries = new List<TypeLibraryDefinition>();
             this.ProcedurePrologs = new List<MaskedPattern>();
         }
 
         public string? Name { get; set; }
         public List<string> TrashedRegisters { get; set; }
+        public List<string> PreservedRegisters { get; set; }
         public List<TypeLibraryDefinition> TypeLibraries { get; set; }
         public List<MaskedPattern> ProcedurePrologs { get; set; }
     }

diff --git a/src/Core/Configuration/RekoConfigurationService.cs b/src/Core/Configuration/RekoConfigurationService.cs
@@ -208,13 +208,18 @@ private TypeLibraryDefinition LoadTypeLibraryReference(TypeLibraryReference_v1 t
         private PlatformArchitectureDefinition LoadPlatformArchitecture(PlatformArchitecture_v1 spa)
         {
             var sTrashedRegs = spa.TrashedRegisters ?? "";
+            var sPreservedRegs = spa.PreservedRegisters ?? "";
             return new PlatformArchitectureDefinition
             {
                 Name = spa.Name,
                 TrashedRegisters = sTrashedRegs
                     .Split(',')
                     .Select(s => s.Trim())
                     .ToList(),
+                PreservedRegisters = sPreservedRegs
+                    .Split(',')
+                    .Select(s => s.Trim())
+                    .ToList(),
                 TypeLibraries = LoadCollection(spa.TypeLibraries, LoadTypeLibraryReference),
                 ProcedurePrologs = LoadMaskedPatterns(spa.ProcedurePrologs)
             };

diff --git a/src/Core/Configuration/RekoConfiguration_v1.cs b/src/Core/Configuration/RekoConfiguration_v1.cs
@@ -357,6 +357,9 @@ public class PlatformArchitecture_v1
         [XmlElement("TrashedRegisters")]
         public string? TrashedRegisters;
 
+        [XmlElement("PreservedRegisters")]
+        public string? PreservedRegisters;
+
         [XmlArray("TypeLibraries")]
         [XmlArrayItem("TypeLibrary")]
         public TypeLibraryReference_v1[]? TypeLibraries;

diff --git a/src/Core/Platform.cs b/src/Core/Platform.cs
@@ -80,6 +80,8 @@ public interface IPlatform
         /// <returns>A set of registers</returns>
         IReadOnlySet<RegisterStorage> TrashedRegisters { get; }
 
+        IReadOnlySet<RegisterStorage> PreservedRegisters { get; }
+
         /// <summary>
         /// The structure member alignment for this platform, measured in
         /// storage units (e.g. bytes). Objects larger than or equal to this
@@ -356,6 +358,7 @@ protected Platform(IServiceProvider services, IProcessorArchitecture arch, strin
             this.PlatformProcedures = new Dictionary<Address, ExternalProcedure>();
             this.ProcedurePrologs = LoadProcedurePrologs();
             this.TrashedRegisters = new HashSet<RegisterStorage>(LoadTrashedRegisters());
+            this.PreservedRegisters = new HashSet<RegisterStorage>(LoadPreservedRegisters());
         }
 
         public IProcessorArchitecture Architecture { get; }
@@ -390,6 +393,7 @@ protected Platform(IServiceProvider services, IProcessorArchitecture arch, strin
         public abstract string DefaultCallingConvention { get; }
 
         public virtual IReadOnlySet<RegisterStorage> TrashedRegisters { get; protected set; }
+        public virtual IReadOnlySet<RegisterStorage> PreservedRegisters { get; protected set; }
 
 
         /// <summary>
@@ -619,6 +623,18 @@ protected RegisterStorage[] LoadTrashedRegisters()
                 .ToArray()!;
         }
 
+        protected RegisterStorage[] LoadPreservedRegisters()
+        {
+            var cfgSvc = Services?.GetService<IConfigurationService>();
+            var pa = cfgSvc?.GetEnvironment(this.PlatformIdentifier)?.Architectures?.SingleOrDefault(a => a.Name == Architecture.Name);
+            if (pa is null)
+                return Array.Empty<RegisterStorage>();
+            return pa.PreservedRegisters
+                .Select(r => Architecture.GetRegister(r))
+                .Where(r => r is { })
+                .ToArray()!;
+        }
+
         public virtual Address? MakeAddressFromConstant(Constant c, bool codeAlign)
         {
             return Architecture.MakeAddressFromConstant(c, codeAlign);

diff --git a/src/Decompiler/Analysis/SccWorker.cs b/src/Decompiler/Analysis/SccWorker.cs
@@ -256,6 +256,7 @@ public SsaTransform ConvertToSsa(Procedure proc)
         private static bool IsStackStorageOfPreservedRegister(
             SsaState ssa,
             IReadOnlySet<RegisterStorage> trashedRegisters,
+            IReadOnlySet<RegisterStorage> preservedRegisters,
             CallBinding use)
         {
             if (use.Storage is not StackStorage)
@@ -264,7 +265,7 @@ private static bool IsStackStorageOfPreservedRegister(
                 return false;
             if (!(ssa.Identifiers[id].IsOriginal))
                 return false;
-            return IsPreservedRegister(trashedRegisters, id.Storage);
+            return IsPreservedRegister(trashedRegisters, preservedRegisters, id.Storage);
         }
 
         /// <summary>
@@ -274,14 +275,18 @@ private static bool IsStackStorageOfPreservedRegister(
         /// to be modified by the ABI of the processor or platform.
         /// </summary>
         /// <param name="trashedRegisters"></param>
+        /// <param name="preservedRegisters"></param>
         /// <param name="stg"></param>
         /// <returns></returns>
         private static bool IsPreservedRegister(
             IReadOnlySet<RegisterStorage> trashedRegisters,
+            IReadOnlySet<RegisterStorage> preservedRegisters,
             Storage stg)
         {
-            if (stg is not RegisterStorage)
+            if (stg is not RegisterStorage reg)
                 return false;
+            if (preservedRegisters.Any(r => r.Covers(reg)))
+                return true;
             if (trashedRegisters.Count == 0)
                 return false;
             return !trashedRegisters.Where(r => r.OverlapsWith(stg)).Any();
@@ -307,13 +312,15 @@ private void RemoveImplicitRegistersFromHellNode(
                     return;
             }
             var trashedRegisters = program.Platform.TrashedRegisters;
+            var preservedRegisters = program.Platform.PreservedRegisters;
             var platform = program.Platform;
             foreach (var use in ci.Uses.ToList())
             {
-                if (IsPreservedRegister(trashedRegisters, use.Storage) ||
+                if (IsPreservedRegister(trashedRegisters, preservedRegisters, use.Storage) ||
                     IsStackStorageOfPreservedRegister(
                         ssa,
                         trashedRegisters,
+                        preservedRegisters,
                         use) ||
                     (use.Storage is RegisterStorage reg &&
                      platform.IsImplicitArgumentRegister(reg)))

diff --git a/src/Decompiler/Analysis/SsaTransform.cs b/src/Decompiler/Analysis/SsaTransform.cs
@@ -271,6 +271,7 @@ public void AddUsesToExitBlock()
                               sid.Identifier.Storage is not MemoryStorage &&
                               sid.Identifier.Storage is not StackStorage &&
                               sid.Identifier.Storage is not TemporaryStorage &&
+                              !IsPreservedByPlatform(sid.Identifier.Storage) &&
                               !existing.Contains(sid.Identifier))
                 .Select(sid => sid.OriginalIdentifier);
             reachingIds = SeparateSequences(reachingIds);
@@ -295,6 +296,16 @@ sid.Identifier.Storage is not TemporaryStorage &&
             });
         }
 
+        //$TODO: make this a method of platform, as some
+        // platforms require register aliasing (EAX, AX, AL etc)
+        // and others don't.
+        private bool IsPreservedByPlatform(Storage storage)
+        {
+            return storage is RegisterStorage reg &&
+                    program.Platform.PreservedRegisters.
+                    Any(r => r.Covers(reg));
+        }
+
         /// <summary>
         /// Remove SCC's of phi assignments whose arguments are other variables in the SCC
         /// or a single external value.

diff --git a/src/Decompiler/Scanning/RtlProcedure.cs b/src/Decompiler/Scanning/RtlProcedure.cs
@@ -20,6 +20,8 @@
 
 using Reko.Core;
 using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Reko.Scanning
 {
@@ -66,5 +68,14 @@ public override string ToString()
         {
             return $"RtlProcedure(entry: {Address}, blocks: {Blocks.Count})";
         }
+
+        [Conditional("DEBUG")]
+        public void Dump()
+        {
+            Debug.Print("    {0}",
+                string.Join(",\r\n    ", this.Blocks
+                    .OrderBy(b => b.Address.ToLinear())
+                    .Select(b => b.Address)));
+        }
     }
 }
diff --git a/src/Decompiler/Scanning/Scanner.cs b/src/Decompiler/Scanning/Scanner.cs
@@ -1141,10 +1141,7 @@ public void ShingleScanProcedures()
         private void Dump(RtlProcedure rtlProc)
         {
             Debug.Print("== {0} ===============", rtlProc.Address);
-            Debug.Print("    {0}",
-                string.Join(",\r\n    ", rtlProc.Blocks
-                    .OrderBy(b => b.Address.ToLinear())
-                    .Select(b => b.Address)));
+            rtlProc.Dump();
         }
 
 

diff --git a/src/Drivers/reko.config b/src/Drivers/reko.config
@@ -404,6 +404,11 @@
           <!--<TypeLibrary Name="macos_classic.xml" />-->
           <TypeLibrary Loader="MpwPascal" Name="macos/MacOSClassicInterfaces.p" />
         </TypeLibraries>
+		  <Architectures>
+			  <Architecture name="m68k">
+				  <PreservedRegisters>a5</PreservedRegisters>
+			  </Architecture>
+		  </Architectures>
       </Environment>
 
       <Environment Name="macOsPpc"

diff --git a/src/Environments/MacOS/Classic/MacOSClassic.cs b/src/Environments/MacOS/Classic/MacOSClassic.cs
@@ -29,6 +29,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using System.IO;
 
 namespace Reko.Environments.MacOS.Classic
 {
@@ -52,6 +53,16 @@ public override bool IsImplicitArgumentRegister(RegisterStorage reg)
             return reg.Number == Registers.a7.Number || reg.Number == Registers.a5.Number;
         }
 
+        public override CParser CreateCParser(TextReader rdr, ParserState? state)
+        {
+            //$TODO: consider making MacOSKeywords for MacOS-specific
+            // extensions to the C.
+            state ??= new ParserState();
+            var lexer = new CLexer(rdr, CLexer.MsvcKeywords);
+            var parser = new CParser(state, lexer);
+            return parser;
+        }
+
         private HashSet<RegisterStorage> CreateTrashedRegisters()
         {
             return new HashSet<RegisterStorage>
@@ -66,7 +77,7 @@ public override CallingConvention GetCallingConvention(string? ccName)
             switch (ccName)
             {
             case "pascal":
-            case "__pascal":
+            case "__pascal":    
                 return new PascalCallingConvention((M68kArchitecture) this.Architecture);
             default:
                 return new M68kCallingConvention((M68kArchitecture) this.Architecture);
@@ -123,7 +134,9 @@ public override void InjectProcedureEntryStatements(Procedure proc, Address addr
             m.MStore(proc.Frame.FramePointer, proc.Frame.Continuation);
             var ptrA5World = EnsureA5Pointer();
             var a5 = proc.Frame.EnsureRegister(Registers.a5);
-            m.Assign(a5, ptrA5World);
+            //m.Assign(a5, this.A5World.Address);
+            m.Assign(a5, m.Word32((uint)(this.A5World.Address.Offset + this.A5Offset)));
+            //m.Assign(a5, ptrA5World);
         }
 
         private Identifier EnsureA5Pointer()

diff --git a/src/ImageLoaders/Llvm/LLVMPlatform.cs b/src/ImageLoaders/Llvm/LLVMPlatform.cs
@@ -44,6 +44,7 @@ public LLVMPlatform(IServiceProvider services)
             this.Name = "LLVM";
             this.StructureMemberAlignment = 4;  //$BUG: is arch-specific.
             this.TrashedRegisters = new HashSet<RegisterStorage>();
+            this.PreservedRegisters = new HashSet<RegisterStorage>();
         }
 #nullable enable
 
@@ -72,6 +73,7 @@ public LLVMPlatform(IServiceProvider services)
         public int StructureMemberAlignment { get; set; }
 
         public IReadOnlySet<RegisterStorage> TrashedRegisters { get; }
+        public IReadOnlySet<RegisterStorage> PreservedRegisters { get; }
 
 
         public Address AdjustProcedureAddress(Address addrCode)

diff --git a/src/UnitTests/Decompiler/Analysis/AnalysisTestBase.cs b/src/UnitTests/Decompiler/Analysis/AnalysisTestBase.cs
@@ -471,6 +471,8 @@ protected void Given_FakeWin32Platform()
                 .Returns((ulong ul, bool b) => Address.Ptr32((uint) ul));
             platformMock.Setup(p => p.TrashedRegisters)
                 .Returns(new HashSet<RegisterStorage>());
+            platformMock.Setup(p => p.PreservedRegisters)
+                .Returns(new HashSet<RegisterStorage>());
             Given_Platform(platformMock.Object);
         }
 	}

diff --git a/src/UnitTests/Decompiler/Analysis/DataFlowAnalysisTests2.cs b/src/UnitTests/Decompiler/Analysis/DataFlowAnalysisTests2.cs
@@ -256,6 +256,7 @@ public void Dfa2_UserDefinedStackArgs()
                     var lex = new CLexer(r, CLexer.MsvcKeywords);
                     return new CParser(s ?? new ParserState(), lex);
                 }));
+            platform.Setup(p => p.PreservedRegisters).Returns(new HashSet<RegisterStorage>());
 
             var dynamicLinker = new Mock<IDynamicLinker>().Object;
             program.Platform = platform.Object;

diff --git a/src/UnitTests/Decompiler/Analysis/UsedRegisterFinderTests.cs b/src/UnitTests/Decompiler/Analysis/UsedRegisterFinderTests.cs
@@ -99,6 +99,7 @@ private Procedure RunTest(string sExp, IProcessorArchitecture arch, Func<Procedu
             var dynamicLinker = new Mock<IDynamicLinker>();
             var platform = new Mock<IPlatform>();
             platform.Setup(p => p.TrashedRegisters).Returns(new HashSet<RegisterStorage>());
+            platform.Setup(p => p.PreservedRegisters).Returns(new HashSet<RegisterStorage>());
             platform.Setup(p => p.PointerType).Returns(arch.PointerType);
             progBuilder.Program.Platform = platform.Object;
             progBuilder.Program.SegmentMap = segmentMap;

diff --git a/subjects/regression.log b/subjects/regression.log