From b8b4814b92c4d808da5a79d1d7311c27b325853f Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 8 Oct 2023 20:48:18 +0100
Subject: Support Patio switch in WASM code gen

---
 .../compiler/backends/wasm/WasmPatioCodeGen.java   | 38 ++++++++++++++++++----
 1 file changed, 32 insertions(+), 6 deletions(-)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/WasmPatioCodeGen.java b/src/main/java/org/shedlang/compiler/backends/wasm/WasmPatioCodeGen.java
index fe01d9c5..16d4b520 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/WasmPatioCodeGen.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/WasmPatioCodeGen.java
@@ -198,11 +198,7 @@ public class WasmPatioCodeGen {
             case PatioIf patioIf -> {
                 context = generateOperand(patioIf.condition(), context);
 
-                var wasmBlockType = new WasmBlockType(
-                    patioIf.targets().stream()
-                        .map(patioTarget -> patioOperandToWasmValueType(patioTarget))
-                        .toList()
-                );
+                var wasmBlockType = generateBlockType(patioIf.targets());
 
                 context = context.enterIfInstruction(wasmBlockType);
                 context = generateBlockBody(patioIf.trueBody(), context);
@@ -307,7 +303,29 @@ public class WasmPatioCodeGen {
             }
 
             case PatioSwitch patioSwitch -> {
-                throw new UnsupportedOperationException("TODO");
+                // TODO: use br_table?
+                var wasmBlockType = generateBlockType(patioSwitch.targets());
+
+                for (var patioSwitchCase : patioSwitch.cases()) {
+                    context = generateOperand(patioSwitch.value(), context);
+                    context = context.addInstruction(new WasmI32Const(patioSwitchCase.value()));
+                    context = context.addInstruction(new WasmI32Eq());
+                    context = context.enterIfInstruction(wasmBlockType);
+                    context = generateBlockBody(patioSwitchCase.body(), context);
+                    context = context.enterElse();
+                }
+
+                context = generateBlockBody(patioSwitch.defaultBody(), context);
+
+                for (var patioSwitchCase : patioSwitch.cases()) {
+                    context = context.exitIfInstruction();
+                }
+
+                for (var patioTarget : Lists.reversed(patioSwitch.targets())) {
+                    context = popIntoPatioLocal(patioTarget, context);
+                }
+
+                yield context;
             }
 
             case PatioUnreachable patioUnreachable ->
@@ -331,6 +349,14 @@ public class WasmPatioCodeGen {
         };
     }
 
+    private static WasmBlockType generateBlockType(List<PatioLocalRef> targets) {
+        return new WasmBlockType(
+            targets.stream()
+                .map(patioTarget -> patioOperandToWasmValueType(patioTarget))
+                .toList()
+        );
+    }
+
     private static Context generateBlockBody(
         PatioBlock block,
         Context context
-- 
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