Add Concrete Syntax for Unstructured Programs in Strata Core

Examples/CFGNondet.core.st

@@ -0,0 +1,23 @@
+program Core;
+
+// Nondeterministic CFG: y is set to either 1 or 2.
+procedure NondetChoice(out y : int)
+spec {
+  ensures (y == 1 || y == 2);
+}
+cfg entry {
+  entry: {
+    goto left, right;
+  }
+  left: {
+    y := 1;
+    goto done;
+  }
+  right: {
+    y := 2;
+    goto done;
+  }
+  done: {
+    return;
+  }
+};

Examples/CFGSimple.core.st

@@ -0,0 +1,48 @@
+program Core;
+
+// A simple deterministic CFG: compute max of two integers.
+procedure Max(x : int, y : int, out m : int)
+spec {
+  ensures (m >= x);
+  ensures (m >= y);
+  ensures (m == x || m == y);
+}
+cfg entry {
+  entry: {
+    branch (x >= y) goto then_branch else else_branch;
+  }
+  then_branch: {
+    m := x;
+    goto done;
+  }
+  else_branch: {
+    m := y;
+    goto done;
+  }
+  done: {
+    return;
+  }
+};
+
+// A CFG with a simple loop: increment y until it reaches n.
+procedure CountUp(n : int, out y : int)
+spec {
+  requires (n >= 0);
+  ensures (y == n);
+}
+cfg entry {
+  entry: {
+    y := 0;
+    goto loop;
+  }
+  loop: {
+    branch (y < n) goto body else done;
+  }
+  body: {
+    y := y + 1;
+    goto loop;
+  }
+  done: {
+    return;
+  }
+};

Strata/Backends/CBMC/CoreToCBMC.lean

@@ -346,7 +346,8 @@ def createImplementationSymbolFromAST (func : Core.Procedure) : Except String CB
 
   -- For now, keep the hardcoded implementation but use function name from AST
   let loc : SourceLoc := { functionName := (func.header.name.toPretty), lineNum := "1" }
-  let stmtJsons ← (func.body.mapM (stmtToJson (I:=CoreLParams) · loc))
+  let bodyStmts ← func.body.getStructured
+  let stmtJsons ← (bodyStmts.mapM (stmtToJson (I:=CoreLParams) · loc))
 
   let implValue := Json.mkObj [
     ("id", "code"),

Strata/Backends/CBMC/GOTO.lean

@@ -5,6 +5,7 @@
 -/
 module
 
+import Strata.Backends.CBMC.GOTO.CoreCFGToGOTOPipeline
 import Strata.Backends.CBMC.GOTO.CoreToCProverGOTO
 import Strata.Backends.CBMC.GOTO.CoreToGOTOPipeline
 import Strata.Backends.CBMC.GOTO.DefaultSymbols

Strata/Backends/CBMC/GOTO/CoreCFGToGOTOPipeline.lean

@@ -0,0 +1,304 @@
+/-
+  Copyright Strata Contributors
+
+  SPDX-License-Identifier: Apache-2.0 OR MIT
+-/
+module
+
+public import Strata.Backends.CBMC.CollectSymbols
+public import Strata.Backends.CBMC.GOTO.CoreToCProverGOTO
+import Strata.Backends.CBMC.GOTO.CoreToGOTOPipeline
+import Strata.Transform.StructuredToUnstructured
+
+/-! ## Core-to-GOTO translation via CFG
+
+Alternative pipeline that translates Core procedures to CProver GOTO by going
+through the CFG representation:
+
+- **Structured body** → `stmtsToCFG` → `coreCFGToGotoTransform`
+- **CFG body** → `coreCFGToGotoTransform`
+
+This coexists with the direct path in `CoreToGOTOPipeline.lean`.
+-/
+
+namespace Strata
+
+public section
+
+/-! ### Rename helpers for Core commands (CmdExt) -/
+
+private def renameCoreCallArg
+    (rn : Std.HashMap String String)
+    : Core.CallArg Core.Expression → Core.CallArg Core.Expression
+  | .inArg e => .inArg (renameExpr rn e)
+  | .inoutArg id => .inoutArg (renameIdent rn id)
+  | .outArg id => .outArg (renameIdent rn id)
+
+private def renameCoreCommand
+    (rn : Std.HashMap String String)
+    : Core.Command → Core.Command
+  | .cmd c => .cmd (renameCmd rn c)
+  | .call procName callArgs md =>
+    .call procName (callArgs.map (renameCoreCallArg rn)) md
+
+private partial def renameCoreStmt
+    (rn : Std.HashMap String String)
+    : Core.Statement → Core.Statement
+  | .cmd c => .cmd (renameCoreCommand rn c)
+  | .block l stmts md =>
+    .block l (stmts.map (renameCoreStmt rn)) md
+  | .ite c t e md =>
+    .ite (c.map (renameExpr rn)) (t.map (renameCoreStmt rn)) (e.map (renameCoreStmt rn)) md
+  | .loop g m i body md =>
+    .loop (g.map (renameExpr rn)) (m.map (renameExpr rn))
+      (i.map (fun (l, e) => (l, renameExpr rn e)))
+      (body.map (renameCoreStmt rn)) md
+  | .exit l md => .exit l md
+  | .funcDecl d md => .funcDecl d md
+  | .typeDecl tc md => .typeDecl tc md
+
+private def renameCoreDetCFG
+    (rn : Std.HashMap String String)
+    (cfg : Core.DetCFG) : Core.DetCFG :=
+  { cfg with blocks := cfg.blocks.map fun (label, block) =>
+    (label, { cmds := block.cmds.map (renameCoreCommand rn),
+              transfer := match block.transfer with
+                | .condGoto cond lt lf md =>
+                  .condGoto (renameExpr rn cond) lt lf md
+                | .finish md => .finish md }) }
+
+/-! ### Core-specific CFG-to-GOTO translation -/
+
+/--
+Translate a Core `DetCFG` to CProver GOTO instructions.
+
+Like `detCFGToGotoTransform` but handles `Core.Command` (which includes
+`CmdExt.call`). The CFG should already have identifiers renamed via
+`renameCoreDetCFG`.
+-/
+def coreCFGToGotoTransform
+    (_Env : Core.Expression.TyEnv) (functionName : String)
+    (cfg : Core.DetCFG)
+    (trans : Imperative.GotoTransform Core.Expression.TyEnv)
+    : Except Std.Format (Imperative.GotoTransform Core.Expression.TyEnv) := do
+  let toExpr := Lambda.LExpr.toGotoExprCtx
+    (TBase := ⟨Core.ExpressionMetadata, Unit⟩) []
+  -- Verify entry block is first
+  match cfg.blocks with
+  | (firstLabel, _) :: _ =>
+    if firstLabel != cfg.entry then
+      throw f!"[coreCFGToGotoTransform] Entry label '{cfg.entry}' does not match \
+               first block label '{firstLabel}'."
+  | [] => pure ()
+  let mut trans := trans
+  let mut pendingPatches : Array (Nat × String) := #[]
+  let mut labelMap : Std.HashMap String Nat := {}
+  let mut loopContracts : Std.HashMap String (Imperative.MetaData Core.Expression) := {}
+  for (label, block) in cfg.blocks do
+    labelMap := labelMap.insert label trans.nextLoc
+    let srcLoc : CProverGOTO.SourceLocation :=
+      { CProverGOTO.SourceLocation.nil with function := functionName }
+    trans := Imperative.emitLabel label srcLoc trans
+    -- Translate each command
+    for cmd in block.cmds do
+      match cmd with
+      | .cmd c =>
+        trans ← Imperative.Cmd.toGotoInstructions trans.T functionName c trans
+      | .call procName callArgs _md =>
+        let lhs := Core.CallArg.getLhs callArgs
+        let args := Core.CallArg.getInputExprs callArgs
+        let argExprs ← args.mapM toExpr
+        let lhsExpr := match lhs with
+          | id :: _ =>
+            let name := Core.CoreIdent.toPretty id
+            let ty := match trans.T.context.types.find? id with
+              | some lty =>
+                match lty.toMonoTypeUnsafe.toGotoType with
+                | .ok gty => gty
+                | .error _ =>
+                  dbg_trace s!"warning: type conversion failed for {name}, defaulting to Integer"
+                  .Integer
+              | none =>
+                dbg_trace s!"warning: no type found for {name}, defaulting to Integer"
+                .Integer
+            CProverGOTO.Expr.symbol name ty
+          | [] => CProverGOTO.Expr.symbol "" .Empty
+        let calleeExpr := CProverGOTO.Expr.symbol procName
+          (CProverGOTO.Ty.mkCode (argExprs.map (·.type)) lhsExpr.type)
+        let callCode := CProverGOTO.Code.functionCall lhsExpr calleeExpr argExprs
+        let inst : CProverGOTO.Instruction :=
+          { type := .FUNCTION_CALL, code := callCode, locationNum := trans.nextLoc }
+        trans := { trans with
+          instructions := trans.instructions.push inst
+          nextLoc := trans.nextLoc + 1 }
+    -- Translate the transfer command
+    match block.transfer with
+    | .condGoto cond lt lf md =>
+      let transferSrcLoc := Imperative.metadataToSourceLoc md functionName trans.sourceText
+      let cond_expr ← toExpr cond
+      let hasLoopContract := md.any fun elem =>
+        elem.fld == Imperative.MetaData.specLoopInvariant ||
+        elem.fld == Imperative.MetaData.specDecreases
+      if hasLoopContract then
+        loopContracts := loopContracts.insert label md
+      let (trans', falseIdx) :=
+        Imperative.emitCondGoto (CProverGOTO.Expr.not cond_expr) transferSrcLoc trans
+      trans := trans'
+      pendingPatches := pendingPatches.push (falseIdx, lf)
+      let (trans', trueIdx) := Imperative.emitUncondGoto transferSrcLoc trans
+      trans := trans'
+      pendingPatches := pendingPatches.push (trueIdx, lt)
+    | .finish _md =>
+      pure ()
+  -- Second pass: resolve labels and annotate backward-edge GOTOs with loop contracts
+  let mut resolvedPatches : List (Nat × Nat) := []
+  for (idx, label) in pendingPatches do
+    match labelMap[label]? with
+    | some targetLoc =>
+      resolvedPatches := (idx, targetLoc) :: resolvedPatches
+      if let some md := loopContracts[label]? then
+        let instLoc := trans.instructions[idx]!.locationNum
+        if targetLoc ≤ instLoc then
+          let mut guard := trans.instructions[idx]!.guard
+          for elem in md do
+            if elem.fld == Imperative.MetaData.specLoopInvariant then
+              if let .expr e := elem.value then
+                let gotoExpr ← toExpr e
+                guard := guard.setNamedField "#spec_loop_invariant" gotoExpr
+            if elem.fld == Imperative.MetaData.specDecreases then
+              if let .expr e := elem.value then
+                let gotoExpr ← toExpr e
+                guard := guard.setNamedField "#spec_decreases" gotoExpr
+          trans := { trans with
+            instructions := trans.instructions.set! idx
+              { trans.instructions[idx]! with guard := guard } }
+    | none =>
+      throw f!"[coreCFGToGotoTransform] Unresolved label '{label}' referenced \
+               by GOTO at instruction index {idx}."
+  return Imperative.patchGotoTargets trans resolvedPatches
+
+/-! ### Pipeline wrapper -/
+
+/--
+Translate a Core procedure to CProver GOTO via the CFG representation.
+
+Mirrors `procedureToGotoCtx` but routes through `stmtsToCFG` +
+`coreCFGToGotoTransform` instead of the direct Stmt-to-GOTO path.
+-/
+def procedureToGotoCtxViaCFG
+    (Env : Core.Expression.TyEnv) (p : Core.Procedure)
+    (sourceText : Option String := none)
+    (axioms : List Core.Axiom := [])
+    (distincts :
+      List (Core.Expression.Ident × List Core.Expression.Expr) := [])
+    : Except Std.Format
+        (CoreToGOTO.CProverGOTO.Context × List Core.Function) := do
+  let pname := Core.CoreIdent.toPretty p.header.name
+  if !p.header.typeArgs.isEmpty then
+    .error f!"[procedureToGotoCtxViaCFG] Polymorphic procedures unsupported."
+  let ret_ty := CProverGOTO.Ty.Empty
+  let formals := p.header.inputs.keys.map Core.CoreIdent.toPretty
+  let formals_tys ← p.header.inputs.values.mapM Lambda.LMonoTy.toGotoType
+  let new_formals := formals.map (CProverGOTO.mkFormalSymbol pname ·)
+  let formals_tys : Map String CProverGOTO.Ty := formals.zip formals_tys
+  let outputs := p.header.outputs.keys.map Core.CoreIdent.toPretty
+  let new_outputs := outputs.map (CProverGOTO.mkLocalSymbol pname ·)
+  let locals_from_body := match p.body with
+    | .structured ss => (Imperative.Block.definedVars ss).map Core.CoreIdent.toPretty
+    | .cfg c => c.blocks.flatMap (fun (_, blk) =>
+        blk.cmds.flatMap Core.Command.definedVars)
+      |>.map Core.CoreIdent.toPretty
+  let new_locals := locals_from_body.map (CProverGOTO.mkLocalSymbol pname ·)
+  let rn : Std.HashMap String String :=
+    (formals.zip new_formals ++ outputs.zip new_outputs ++ locals_from_body.zip new_locals).foldl
+      (init := {}) fun m (k, v) => m.insert k v
+  -- Seed the type environment with renamed input and output parameter types
+  let inputEntries : Map Core.Expression.Ident Core.Expression.Ty :=
+    (new_formals.zip p.header.inputs.values).map fun (n, ty) =>
+      (((n : Core.CoreIdent)), .forAll [] ty)
+  let outputEntries : Map Core.Expression.Ident Core.Expression.Ty :=
+    (new_outputs.zip p.header.outputs.values).map fun (n, ty) =>
+      (((n : Core.CoreIdent)), .forAll [] ty)
+  let Env' : Core.Expression.TyEnv :=
+    Lambda.TEnv.addInNewestContext (T := ⟨Core.ExpressionMetadata, Unit⟩)
+      Env (inputEntries ++ outputEntries)
+  -- Emit axioms as ASSUME instructions
+  let mut axiomInsts : Array CProverGOTO.Instruction := #[]
+  let mut axiomLoc : Nat := 0
+  for ax in axioms do
+    let gotoExpr ← Lambda.LExpr.toGotoExprCtx
+      (TBase := ⟨Core.ExpressionMetadata, Unit⟩) [] ax.e
+    if gotoExpr.hasUnsupportedQuantifierTypes then continue
+    axiomInsts := axiomInsts.push
+      { type := .ASSUME, locationNum := axiomLoc,
+        guard := gotoExpr,
+        sourceLoc := { CProverGOTO.SourceLocation.nil with
+          function := pname, comment := s!"axiom {ax.name}" } }
+    axiomLoc := axiomLoc + 1
+  -- Emit distinct declarations as pairwise != ASSUME instructions
+  for (dname, exprs) in distincts do
+    let gotoExprs ← exprs.mapM
+      (Lambda.LExpr.toGotoExprCtx (TBase := ⟨Core.ExpressionMetadata, Unit⟩) [])
+    for i in List.range gotoExprs.length do
+      for j in List.range gotoExprs.length do
+        if i < j then
+          let ei := gotoExprs[i]!
+          let ej := gotoExprs[j]!
+          let neqExpr : CProverGOTO.Expr :=
+            { id := .binary .NotEqual, type := .Boolean, operands := [ei, ej] }
+          let srcLoc : CProverGOTO.SourceLocation :=
+            { CProverGOTO.SourceLocation.nil with
+                function := pname
+                comment := s!"distinct {Core.CoreIdent.toPretty dname}" }
+          axiomInsts := axiomInsts.push
+            { type := .ASSUME, locationNum := axiomLoc, guard := neqExpr, sourceLoc := srcLoc }
+          axiomLoc := axiomLoc + 1
+  -- Build the CFG (from structured body or use existing CFG)
+  let (cfg, liftedFuncs) ← match p.body with
+    | .structured ss => do
+      let (liftedFuncs, body) ← collectFuncDecls ss
+      let renamedBody := body.map (renameCoreStmt rn)
+      let cfg := Imperative.stmtsToCFG renamedBody
+      pure (cfg, liftedFuncs)
+    | .cfg c => do
+      let cfg := renameCoreDetCFG rn c
+      pure (cfg, [])
+  -- Translate CFG to GOTO
+  let ans ← coreCFGToGotoTransform Env' pname cfg
+    { instructions := axiomInsts, nextLoc := axiomLoc, T := Env', sourceText := sourceText }
+  let ending_insts : Array CProverGOTO.Instruction :=
+    #[{ type := .END_FUNCTION, locationNum := ans.nextLoc + 1 }]
+  let pgm := { name := pname,
+               parameterIdentifiers := new_formals.toArray,
+               instructions := ans.instructions ++ ending_insts }
+  -- Translate procedure contracts
+  let mut contracts : List (String × Lean.Json) := []
+  let preExprs := p.spec.preconditions.values.filter (fun c => c.attr == .Default)
+    |>.map (fun c => renameExpr rn c.expr)
+  let postExprs := p.spec.postconditions.values.filter (fun c => c.attr == .Default)
+    |>.map (fun c => renameExpr rn c.expr)
+  let toGotoExpr := Lambda.LExpr.toGotoExprCtx
+    (TBase := ⟨Core.ExpressionMetadata, Unit⟩) []
+  if !preExprs.isEmpty then
+    let preGoto ← preExprs.mapM toGotoExpr
+    let preJson ← (preGoto.mapM CProverGOTO.exprToJson).mapError (fun e => f!"{e}")
+    contracts := contracts ++ [("#spec_requires",
+      Lean.Json.mkObj [("id", ""), ("sub", Lean.Json.arr preJson.toArray)])]
+  if !postExprs.isEmpty then
+    let postGoto ← postExprs.mapM toGotoExpr
+    let postJson ← (postGoto.mapM CProverGOTO.exprToJson).mapError (fun e => f!"{e}")
+    contracts := contracts ++ [("#spec_ensures",
+      Lean.Json.mkObj [("id", ""), ("sub", Lean.Json.arr postJson.toArray)])]
+  -- Build localTypes map for output parameters
+  let output_tys ← p.header.outputs.values.mapM Lambda.LMonoTy.toGotoType
+  let localTypes : Std.HashMap String CProverGOTO.Ty :=
+    (outputs.zip output_tys).foldl (init := {}) fun m (k, v) => m.insert k v
+  let ctx : CoreToGOTO.CProverGOTO.Context :=
+    { program := pgm, formals := formals_tys, ret := ret_ty,
+      locals := outputs ++ locals_from_body, contracts := contracts,
+      localTypes := localTypes }
+  return (ctx, liftedFuncs)
+
+end -- public section
+
+end Strata