Add if instruction

7 files changed, 78 insertions, 11 deletions

diff --git a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGen.java b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGen.java
index e2236dcc..2f20e55b 100644
--- a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGen.java
+++ b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGen.java
@@ -147,6 +147,9 @@ public class LlvmCodeGen {
                 yield context.push(fieldValue);
             }
 
+            case IfInstruction if_ ->
+                throw new UnsupportedOperationException("TODO");
+
             case IntAddInstruction intAdd ->
                 generateBinaryOperation(
                     (target, left, right, operationContext) ->
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/WasmCodeGen.java b/src/main/java/org/shedlang/compiler/backends/wasm/WasmCodeGen.java
index a9ee98ac..e7ebff16 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/WasmCodeGen.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/WasmCodeGen.java
@@ -179,6 +179,9 @@ public class WasmCodeGen {
                 );
             }
 
+            case IfInstruction if_ ->
+                throw new UnsupportedOperationException("TODO");
+
             case IntAddInstruction intAdd ->
                 context.addInstruction(new WasmI32Add());
 
diff --git a/src/main/java/org/shedlang/compiler/stackir/InstructionSerializer.java b/src/main/java/org/shedlang/compiler/stackir/InstructionSerializer.java
index baaf4b49..17d778df 100644
--- a/src/main/java/org/shedlang/compiler/stackir/InstructionSerializer.java
+++ b/src/main/java/org/shedlang/compiler/stackir/InstructionSerializer.java
@@ -12,11 +12,7 @@ public class InstructionSerializer {
     }
 
     public static void serializeInstructions(List<Instruction> instructions, StringBuilder builder) {
-        var tree = treeListIndented(
-            instructions.stream()
-                .map(instruction -> toTree(instruction))
-                .toList()
-        );
+        var tree = instructionsToTree(instructions);
         serializeTree(tree, builder, 0);
     }
 
@@ -25,6 +21,14 @@ public class InstructionSerializer {
         serializeTree(tree, builder, 0);
     }
 
+    private static Tree instructionsToTree(List<Instruction> instructions) {
+        return treeListIndented(
+            instructions.stream()
+                .map(instruction -> toTree(instruction))
+                .toList()
+        );
+    }
+
     private static Tree toTree(Instruction instruction) {
         return switch (instruction) {
             case CallInstruction callInstruction -> 
@@ -63,11 +67,7 @@ public class InstructionSerializer {
                             .map(freeVariable -> treeString(freeVariable.name()))
                             .toList()
                     )),
-                    treeNamed("body", treeListIndented(
-                        defineFunctionInstruction.body().stream()
-                            .map(bodyInstruction -> toTree(bodyInstruction))
-                            .toList()
-                    ))
+                    treeNamed("body", instructionsToTree(defineFunctionInstruction.body()))
                 );
             
             case DiscardInstruction discardInstruction ->
@@ -82,6 +82,13 @@ public class InstructionSerializer {
                     treeString(fieldLoad.fieldName())
                 );
 
+            case IfInstruction if_ ->
+                treeListIndented(
+                    treeIdentifier("if"),
+                    instructionsToTree(if_.trueBody()),
+                    instructionsToTree(if_.falseBody())
+                );
+
             case IntAddInstruction intAdd ->
                 treeList(treeIdentifier("int-add"));
 
diff --git a/src/main/java/org/shedlang/compiler/stackir/instructions/IfInstruction.java b/src/main/java/org/shedlang/compiler/stackir/instructions/IfInstruction.java
new file mode 100644
index 00000000..df09859f
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/stackir/instructions/IfInstruction.java
@@ -0,0 +1,18 @@
+package org.shedlang.compiler.stackir.instructions;
+
+
+import org.shedlang.compiler.sources.Source;
+
+import java.util.List;
+
+/**
+ * Pop a value from a stack, and assume it is a Bool. If it is true, execute the
+ * instructions in the "true" body, otherwise execute the instructions in the
+ * "false" body.
+ */
+public record IfInstruction(
+    List<Instruction> trueBody,
+    List<Instruction> falseBody,
+    Source source
+) implements Instruction {
+}
diff --git a/src/main/java/org/shedlang/compiler/stackir/instructions/Instruction.java b/src/main/java/org/shedlang/compiler/stackir/instructions/Instruction.java
index a1ab0a39..80593264 100644
--- a/src/main/java/org/shedlang/compiler/stackir/instructions/Instruction.java
+++ b/src/main/java/org/shedlang/compiler/stackir/instructions/Instruction.java
@@ -3,7 +3,7 @@ package org.shedlang.compiler.stackir.instructions;
 import org.shedlang.compiler.sources.Source;
 
 public sealed interface Instruction
-    permits CallInstruction, DefineFunctionInstruction, DiscardInstruction, FieldLoadInstruction, IntAddInstruction, IntEqualsInstruction, IntNotEqualInstruction, IntSubInstruction, LocalLoadInstruction, LocalStoreInstruction, NamespaceFieldStoreInstruction, NamespaceImportInstruction, PushBoolInstruction, PushIntInstruction, PushStringInstruction, PushUnitInstruction, ReturnInstruction, StringAddInstruction {
+    permits CallInstruction, DefineFunctionInstruction, DiscardInstruction, FieldLoadInstruction, IfInstruction, IntAddInstruction, IntEqualsInstruction, IntNotEqualInstruction, IntSubInstruction, LocalLoadInstruction, LocalStoreInstruction, NamespaceFieldStoreInstruction, NamespaceImportInstruction, PushBoolInstruction, PushIntInstruction, PushStringInstruction, PushUnitInstruction, ReturnInstruction, StringAddInstruction {
 
     Source source();
 }
diff --git a/src/test/java/org/shedlang/compiler/stackir/InstructionSerializerTests.java b/src/test/java/org/shedlang/compiler/stackir/InstructionSerializerTests.java
index 3ce690b2..72056a3e 100644
--- a/src/test/java/org/shedlang/compiler/stackir/InstructionSerializerTests.java
+++ b/src/test/java/org/shedlang/compiler/stackir/InstructionSerializerTests.java
@@ -76,6 +76,35 @@ public class InstructionSerializerTests {
     }
 
     @Test
+    public void canSerializeIf() {
+        var instruction = Instructions.if_(
+            List.of(
+                Instructions.pushUnit()
+            ),
+            List.of(
+                Instructions.localLoad("x"),
+                Instructions.discard(),
+                Instructions.pushBool(true)
+            )
+        );
+
+        var string = serialize(instruction);
+
+        assertThat(string, equalTo("""
+            (
+                if
+                (
+                    (push-unit)
+                )
+                (
+                    (local-load "x")
+                    (discard)
+                    (push-bool true)
+                )
+            )"""));
+    }
+
+    @Test
     public void canSerializeIntAdd() {
         var instruction = Instructions.intAdd();
 
diff --git a/src/test/java/org/shedlang/compiler/stackir/instructions/Instructions.java b/src/test/java/org/shedlang/compiler/stackir/instructions/Instructions.java
index df8b193b..131207b8 100644
--- a/src/test/java/org/shedlang/compiler/stackir/instructions/Instructions.java
+++ b/src/test/java/org/shedlang/compiler/stackir/instructions/Instructions.java
@@ -22,6 +22,13 @@ public class Instructions {
         return new FieldLoadInstruction(namespaceName, fieldName, Sources.NULL);
     }
 
+    public static Instruction if_(
+        List<Instruction> trueBody,
+        List<Instruction> falseBody
+    ) {
+        return new IfInstruction(trueBody, falseBody, Sources.NULL);
+    }
+
     public static Instruction intAdd() {
         return new IntAddInstruction(Sources.NULL);
     }