Imclin: Reorder basic blocks

Lenart12 · Apr 12, 2023 · 7cb4de5 · 7cb4de5
1 parent a3eb49b
commit 7cb4de5
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Showing 3 changed files with 109 additions and 7 deletions.
diff --git a/prev23/src/prev23/phase/imcgen/CodeGenerator.java b/prev23/src/prev23/phase/imcgen/CodeGenerator.java
@@ -283,22 +283,28 @@ public ImcInstr visit(AstExprStmt exprStmt, Boolean is_return) {
 
     @Override
     public ImcInstr visit(AstIfStmt ifStmt, Boolean is_return) {
+        var start_label = new MemLabel();
         var positive_label = new MemLabel();
+        var negative_label =  new MemLabel();
         var end_label = new MemLabel();
-        var negative_label = (ifStmt.elseStmt != null) ? new MemLabel() : end_label;
 
         var stmts = new Vector<>(List.of(
+            new ImcJUMP(start_label),
+            new ImcLABEL(start_label),
             new ImcCJUMP(accept_expr(ifStmt.cond), positive_label, negative_label),
             new ImcLABEL(positive_label),
             accept_stmt(ifStmt.thenStmt, false),
             new ImcJUMP(end_label),
             new ImcLABEL(negative_label)
         ));
 
-        if (ifStmt.elseStmt != null) stmts.addAll(List.of(
-           accept_stmt(ifStmt.elseStmt, false),
-           new ImcJUMP(end_label),
-           new ImcLABEL(end_label)
+        if (ifStmt.elseStmt != null) stmts.add(
+           accept_stmt(ifStmt.elseStmt, false)
+        );
+
+        stmts.addAll(List.of(
+            new ImcJUMP(end_label),
+            new ImcLABEL(end_label)
         ));
 
         return declare_stmt(ifStmt, new ImcSTMTS(stmts), is_return);
@@ -316,10 +322,15 @@ public ImcInstr visit(AstStmts stmts, Boolean is_return) {
 
     @Override
     public ImcInstr visit(AstWhileStmt whileStmt, Boolean is_return) {
+        var start_label = new MemLabel();
         var condition_label = new MemLabel();
         var body_label = new MemLabel();
         var end_label = new MemLabel();
+
         return declare_stmt(whileStmt, new ImcSTMTS(new Vector<>(List.of(
+                new ImcJUMP(start_label),
+                new ImcLABEL(start_label),
+                new ImcJUMP(condition_label),
                 new ImcLABEL(condition_label),
                 new ImcCJUMP(accept_expr(whileStmt.cond), body_label, end_label),
                 new ImcLABEL(body_label),

diff --git a/prev23/src/prev23/phase/imclin/ChunkGenerator.java b/prev23/src/prev23/phase/imclin/ChunkGenerator.java
@@ -2,6 +2,7 @@
 
 import java.util.*;
 
+import prev23.common.report.Report;
 import prev23.data.ast.tree.decl.*;
 import prev23.data.ast.tree.expr.*;
 import prev23.data.ast.visitor.*;
@@ -26,7 +27,9 @@ public Object visit(AstFunDecl funDecl, Object o) {
         body.add(0, new ImcLABEL(entry_label));
         body.add(new ImcJUMP(exit_label));
 
-        ImcLin.addCodeChunk(new LinCodeChunk(frame, body, entry_label, exit_label));
+        var fixed = fix_basic_blocks(body, entry_label, exit_label);
+
+        ImcLin.addCodeChunk(new LinCodeChunk(frame, fixed, entry_label, exit_label));
 
         funDecl.stmt.accept(this, o);
 
@@ -53,4 +56,92 @@ public Object visit(AstAtomExpr atomExpr, Object o) {
        }
        return null;
     }
+
+    private Vector<ImcStmt> fix_basic_blocks(Vector<ImcStmt> stmts, MemLabel entry_label, MemLabel exit_label) {
+        HashMap<MemLabel, Vector<ImcStmt>> basic_blocks = new HashMap<>();
+
+        Vector<ImcStmt> block = null;
+
+        for (var stmt : stmts) {
+            if (stmt instanceof ImcLABEL label) {
+                if (block != null) {
+                    throw new Report.InternalError();
+                }
+                block = new Vector<>();
+                basic_blocks.put(label.label, block);
+            }
+
+            // Skip dead code
+            if (block == null) continue;
+
+            block.add(stmt);
+
+            if (stmt instanceof ImcJUMP || stmt instanceof ImcCJUMP) {
+                block = null;
+            }
+        }
+
+        if (block != null) {
+            throw new Report.InternalError();
+        }
+
+        var fixed = new Vector<ImcStmt>();
+
+        // Insert basic blocks starting with entry_label
+        var next_blocks = new LinkedList<MemLabel>();
+        next_blocks.addFirst(entry_label);
+        while(!next_blocks.isEmpty()) {
+            var next_block_label = next_blocks.removeFirst();
+
+            // Skip exit block
+            if (next_block_label.name.equals(exit_label.name)) continue;
+
+            var next_block = basic_blocks.get(next_block_label);
+
+            if (next_block == null) {
+                continue;
+            }
+
+            fixed.addAll(next_block);
+            basic_blocks.remove(next_block_label);
+
+            var next_jump = next_block.lastElement();
+
+            if (next_jump instanceof ImcJUMP jump) {
+                next_blocks.addFirst(jump.label);
+            } else if (next_jump instanceof ImcCJUMP cjump) {
+                next_blocks.addFirst(cjump.posLabel);
+                next_blocks.addFirst(cjump.negLabel);
+            }
+        }
+
+        var targeted_labels = new HashSet<MemLabel>();
+        targeted_labels.add(entry_label);
+        // Remove sequential JUMP L -> LABEL L
+        for (int i = 0; i < fixed.size(); i++) {
+            if (fixed.get(i) instanceof ImcCJUMP cjump) {
+                targeted_labels.add(cjump.posLabel);
+                targeted_labels.add(cjump.negLabel);
+            } else if (fixed.get(i) instanceof ImcJUMP jump) {
+                if (i + 1 < fixed.size() && fixed.get(i + 1) instanceof ImcLABEL label && jump.label == label.label) {
+                    fixed.remove(i--);
+                } else {
+                    targeted_labels.add(jump.label);
+                }
+            }
+        }
+
+        var removed = 0;
+        // Remove unused labels
+        for (int i = 0; i < fixed.size(); i++) {
+            if (fixed.get(i) instanceof ImcLABEL label) {
+                if (!targeted_labels.contains(label.label)) {
+                    fixed.remove(i--);
+                    removed++;
+                }
+            }
+        }
+
+        return fixed;
+    }
 }
diff --git a/prev23/src/prev23/phase/memory/MemEvaluator.java b/prev23/src/prev23/phase/memory/MemEvaluator.java
@@ -161,7 +161,7 @@ public Object visit(AstAtomExpr atomExpr, MemScope scope) {
             return null;
 
         var value = atomExpr.value.replace("\\\"", "\"");
-        var const_size = (value.length() + 1) * (new SemChar().size());
+        var const_size = (value.length() - 1) * (new SemChar().size());
 
         Memory.strings.put(atomExpr, new MemAbsAccess(const_size, new MemLabel(), value));
         return null;