From cccf9edd15ad2148dadd09fa5a2a94edf9dbbf77 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 3 Apr 2026 10:11:21 +0100
Subject: Compile int-sub in patio-to-cranelift

---
 patio-to-cranelift/src/lib.rs                      | 24 ++++++++++++++--
 .../shedlang/compiler/patio/PatioExampleTests.java | 33 ++++++++++++++++++++++
 2 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/patio-to-cranelift/src/lib.rs b/patio-to-cranelift/src/lib.rs
index bef7e426..d9ff6c5d 100644
--- a/patio-to-cranelift/src/lib.rs
+++ b/patio-to-cranelift/src/lib.rs
@@ -8,9 +8,9 @@ use crate::{
     patio_generated::patio::{
         PatioBlock, PatioBoolToInt, PatioCall, PatioCompilationUnitElement,
         PatioCompilationUnitElementValue, PatioFunctionDefinition, PatioIf, PatioInstruction,
-        PatioInstructionValue, PatioIntAdd, PatioIntToBool, PatioIntValue, PatioIntValueValue,
-        PatioLocal, PatioLocalRef, PatioLocalStore, PatioLocalType, PatioOperand,
-        PatioOperandValue, PatioReturn, PatioReturnVoid, PatioType, PatioTypeValue,
+        PatioInstructionValue, PatioIntAdd, PatioIntSub, PatioIntToBool, PatioIntValue,
+        PatioIntValueValue, PatioLocal, PatioLocalRef, PatioLocalStore, PatioLocalType,
+        PatioOperand, PatioOperandValue, PatioReturn, PatioReturnVoid, PatioType, PatioTypeValue,
         PatioVisibility,
     },
 };
@@ -221,6 +221,13 @@ fn compile_instruction(
             compile_int_add(int_add, context);
         }
 
+        PatioInstructionValue::PatioIntSub => {
+            let int_sub = instruction
+                .value_instruction_value_as_patio_int_sub()
+                .unwrap();
+            compile_int_sub(int_sub, context);
+        }
+
         PatioInstructionValue::PatioIntToBool => {
             let int_to_bool = instruction
                 .value_instruction_value_as_patio_int_to_bool()
@@ -362,6 +369,17 @@ fn compile_int_add(int_add: PatioIntAdd<'_>, context: &mut CompilerFunctionConte
     def_destination(int_add.destination(), cranelift_result, context);
 }
 
+fn compile_int_sub(int_sub: PatioIntSub<'_>, context: &mut CompilerFunctionContext<'_>) {
+    let cranelift_left = compile_operand(int_sub.left(), context);
+    let cranelift_right = compile_operand(int_sub.right(), context);
+    let cranelift_result = context
+        .function_builder
+        .ins()
+        .isub(cranelift_left, cranelift_right);
+
+    def_destination(int_sub.destination(), cranelift_result, context);
+}
+
 fn compile_int_to_bool(int_to_bool: PatioIntToBool<'_>, context: &mut CompilerFunctionContext<'_>) {
     let cranelift_value = compile_operand(int_to_bool.value(), context);
 
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioExampleTests.java b/src/test/java/org/shedlang/compiler/patio/PatioExampleTests.java
index 08f4a50f..25219c9e 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioExampleTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioExampleTests.java
@@ -365,6 +365,39 @@ public abstract class PatioExampleTests {
         ));
     }
 
+    @Test
+    public void intSub() throws IOException, InterruptedException {
+        var patioFunction = PatioFunctionDefinition.builder()
+            .withName(FUNCTION_NAME)
+            .withReturnType(PatioTypes.VOID)
+            .addLocal(Patio.val("x", PatioTypes.INT))
+            .addLocal(Patio.val("y", PatioTypes.INT))
+            .addLocal(Patio.val("z", PatioTypes.INT))
+            .addBodyInstruction(Patio.localStore(
+                Patio.localRef("x"),
+                Patio.intConst(47)
+            ))
+            .addBodyInstruction(Patio.localStore(
+                Patio.localRef("y"),
+                Patio.intConst(5)
+            ))
+            .addBodyInstruction(Patio.intSub(
+                Patio.localRef("z"),
+                Patio.localRef("x"),
+                Patio.localRef("y")
+            ))
+            .addBodyInstruction(emitInt(Patio.localRef("z")))
+            .addBodyInstruction(Patio.returnVoid())
+            .build();
+        var patio = Patio.compilationUnit(List.of(patioFunction));
+
+        var result = run(patio);
+
+        assertThat(result, isSequence(
+            isInt(42)
+        ));
+    }
+
     @Test
     public void switchWithUnreachableDefault() throws IOException, InterruptedException {
         var patioFunction = PatioFunctionDefinition.builder()
-- 
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