Support Patio switch with reachable default in LLVM code gen

2 files changed, 22 insertions, 17 deletions

diff --git a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGenLocalVariableSpace.java b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGenLocalVariableSpace.java
index 989c657f..fb65ffb8 100644
--- a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGenLocalVariableSpace.java
+++ b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmCodeGenLocalVariableSpace.java
@@ -27,7 +27,8 @@ public enum LlvmCodeGenLocalVariableSpace {
     SIZE("size"),
     SWITCH_CASE_START("switchCaseStart"),
     SWITCH_CASE_END("switchCaseEnd"),
-    SWITCH_DEFAULT("switchDefault"),
+    SWITCH_DEFAULT_START("switchDefaultStart"),
+    SWITCH_DEFAULT_END("switchDefaultEnd"),
     SWITCH_END("switchEnd"),
     TEMPORARY("tmp");
 
diff --git a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmPatioCodeGen.java b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmPatioCodeGen.java
index fce77ab8..e431a851 100644
--- a/src/main/java/org/shedlang/compiler/backends/llvm/LlvmPatioCodeGen.java
+++ b/src/main/java/org/shedlang/compiler/backends/llvm/LlvmPatioCodeGen.java
@@ -300,8 +300,8 @@ public class LlvmPatioCodeGen {
                 context = generateBranches(
                     patioIf.targets(),
                     List.of(
-                        new Branch(ifTrueStartLabel, Optional.of(ifTrueEndLabel), patioIf.trueBody()),
-                        new Branch(ifFalseStartLabel, Optional.of(ifFalseEndLabel), patioIf.falseBody())
+                        new Branch(ifTrueStartLabel, ifTrueEndLabel, patioIf.trueBody()),
+                        new Branch(ifFalseStartLabel, ifFalseEndLabel, patioIf.falseBody())
                     ),
                     endLabel,
                     context
@@ -480,11 +480,17 @@ public class LlvmPatioCodeGen {
                 ));
 
             case PatioSwitch patioSwitch -> {
-                var defaultLabelResult = context.allocateLocalName(
-                    LlvmCodeGenLocalVariableSpace.SWITCH_DEFAULT
+                var switchDefaultStartLabelResult = context.allocateLocalName(
+                    LlvmCodeGenLocalVariableSpace.SWITCH_DEFAULT_START
                 );
-                var switchDefaultLabel = defaultLabelResult.value();
-                context = defaultLabelResult.context();
+                var switchDefaultStartLabel = switchDefaultStartLabelResult.value();
+                context = switchDefaultStartLabelResult.context();
+
+                var switchDefaultEndLabelResult = context.allocateLocalName(
+                    LlvmCodeGenLocalVariableSpace.SWITCH_DEFAULT_END
+                );
+                var switchDefaultEndLabel = switchDefaultEndLabelResult.value();
+                context = switchDefaultEndLabelResult.context();
 
                 var switchEndLabelResult = context.allocateLocalName(
                     LlvmCodeGenLocalVariableSpace.SWITCH_END
@@ -511,7 +517,7 @@ public class LlvmPatioCodeGen {
 
                     branches.add(new Branch(
                         caseStartLabel,
-                        Optional.of(caseEndLabel),
+                        caseEndLabel,
                         patioSwitchCase.body()
                     ));
 
@@ -522,16 +528,15 @@ public class LlvmPatioCodeGen {
                 }
 
                 branches.add(new Branch(
-                    switchDefaultLabel,
-                    // TODO: handle defaults that don't terminate
-                    Optional.empty(),
+                    switchDefaultStartLabel,
+                    switchDefaultEndLabel,
                     patioSwitch.defaultBody()
                 ));
 
                 context = context.addTerminatorInstruction(new LlvmSwitch(
                     LlvmTypes.INT_64,
                     patioOperandToLlvmOperand(patioSwitch.value(), context),
-                    switchDefaultLabel,
+                    switchDefaultStartLabel,
                     llvmSwitchCases
                 ));
 
@@ -587,7 +592,7 @@ public class LlvmPatioCodeGen {
 
     record Branch(
         LlvmVariableLocal startLabel,
-        Optional<LlvmVariableLocal> endLabel,
+        LlvmVariableLocal endLabel,
         PatioBlock body
     ) {}
 
@@ -607,17 +612,16 @@ public class LlvmPatioCodeGen {
                 .anyMatch(instruction -> instruction instanceof PatioUnreachable);
 
             if (!endIsUnreachable) {
-                var branchEndLabel = branch.endLabel.orElseThrow();
                 context = context.addTerminatorInstruction(new LlvmBrUnconditional(
-                    branchEndLabel
+                    branch.endLabel
                 ));
                 // TODO: only allow basic block label to be set with terminator instruction?
-                context = context.setBasicBlockLabel(branchEndLabel.name());
+                context = context.setBasicBlockLabel(branch.endLabel.name());
                 context = context.addTerminatorInstruction(new LlvmBrUnconditional(
                     endLabel
                 ));
 
-                phiPredecessors.add(new PhiPredecessor(branch.body, branchEndLabel));
+                phiPredecessors.add(new PhiPredecessor(branch.body, branch.endLabel));
             }
         }