From 9e3240218f4ff59258eeb24649108f5d93a2b427 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <eduard@urbach.dev>
Date: Sat, 2 Aug 2025 17:35:38 +0200
Subject: [PATCH] Improved phi construction in branches

---
 src/core/compileIf.go          | 10 +++++-----
 src/core/compileSwitch.go      |  9 +++------
 src/ssa/Block.go               |  5 +++++
 src/ssa/Branch.go              |  2 +-
 tests/phi-advanced.q           | 19 +++++++++++++++++++
 tests/{else.q => phi-simple.q} |  4 ++--
 tests/phi.q                    |  8 ++++----
 tests/tests_test.go            |  5 +++--
 8 files changed, 42 insertions(+), 20 deletions(-)
 create mode 100644 tests/phi-advanced.q
 rename tests/{else.q => phi-simple.q} (72%)

diff --git a/src/core/compileIf.go b/src/core/compileIf.go
index 000f9a6..7409c59 100644
--- a/src/core/compileIf.go
+++ b/src/core/compileIf.go
@@ -14,9 +14,9 @@ func (f *Function) compileIf(branch *ast.If) error {
 	endBlock := ssa.NewBlock(endLabel)
 	beforeIf := f.Block()
 	beforeIf.AddSuccessor(thenBlock)
-	thenBlock.AddSuccessor(endBlock)
 
 	if branch.Else == nil {
+		beforeIf.AddSuccessor(endBlock)
 		err := f.compileCondition(branch.Condition, thenBlock, endBlock)
 
 		if err != nil {
@@ -31,20 +31,18 @@ func (f *Function) compileIf(branch *ast.If) error {
 			return err
 		}
 
+		f.Block().AddSuccessor(endBlock)
 		f.Append(&ssa.Jump{To: endBlock})
-		beforeIf.AddSuccessor(endBlock)
 	} else {
 		elseLabel := f.CreateLabel("if.else", f.Count.Branch)
 		elseBlock := ssa.NewBlock(elseLabel)
+		beforeIf.AddSuccessor(elseBlock)
 		err := f.compileCondition(branch.Condition, thenBlock, elseBlock)
 
 		if err != nil {
 			return err
 		}
 
-		beforeIf.AddSuccessor(elseBlock)
-		elseBlock.AddSuccessor(endBlock)
-
 		// Append the if.then block
 		f.AddBlock(thenBlock)
 		err = f.compileAST(branch.Body)
@@ -53,6 +51,7 @@ func (f *Function) compileIf(branch *ast.If) error {
 			return err
 		}
 
+		f.Block().AddSuccessor(endBlock)
 		f.Append(&ssa.Jump{To: endBlock})
 
 		// Append the if.else block
@@ -63,6 +62,7 @@ func (f *Function) compileIf(branch *ast.If) error {
 			return err
 		}
 
+		f.Block().AddSuccessor(endBlock)
 		f.Append(&ssa.Jump{To: endBlock})
 	}
 
diff --git a/src/core/compileSwitch.go b/src/core/compileSwitch.go
index 9f120c4..96e1830 100644
--- a/src/core/compileSwitch.go
+++ b/src/core/compileSwitch.go
@@ -19,8 +19,7 @@ func (f *Function) compileSwitch(s *ast.Switch) error {
 				return err
 			}
 
-			defaultBlock := f.Block()
-			defaultBlock.AddSuccessor(exitBlock)
+			f.Block().AddSuccessor(exitBlock)
 			f.Append(&ssa.Jump{To: exitBlock})
 			f.AddBlock(exitBlock)
 			break
@@ -41,7 +40,6 @@ func (f *Function) compileSwitch(s *ast.Switch) error {
 		caseBlock := f.Block()
 		caseBlock.AddSuccessor(thenBlock)
 		caseBlock.AddSuccessor(elseBlock)
-
 		err := f.compileCondition(branch.Condition, thenBlock, elseBlock)
 
 		if err != nil {
@@ -55,9 +53,8 @@ func (f *Function) compileSwitch(s *ast.Switch) error {
 			return err
 		}
 
-		thenBlock.Append(&ssa.Jump{To: exitBlock})
-		thenBlock.AddSuccessor(exitBlock)
-
+		f.Block().Append(&ssa.Jump{To: exitBlock})
+		f.Block().AddSuccessor(exitBlock)
 		f.AddBlock(elseBlock)
 	}
 
diff --git a/src/ssa/Block.go b/src/ssa/Block.go
index 473c579..58da555 100644
--- a/src/ssa/Block.go
+++ b/src/ssa/Block.go
@@ -180,4 +180,9 @@ func (block *Block) ReplaceAll(old Value, new Value) {
 	for _, instr := range block.Instructions {
 		instr.Replace(old, new)
 	}
+}
+
+// String returns the block label.
+func (block *Block) String() string {
+	return block.Label
 }
\ No newline at end of file
diff --git a/src/ssa/Branch.go b/src/ssa/Branch.go
index 1949106..4213410 100644
--- a/src/ssa/Branch.go
+++ b/src/ssa/Branch.go
@@ -32,5 +32,5 @@ func (v *Branch) Replace(old Value, new Value) {
 }
 
 func (v *Branch) String() string {
-	return fmt.Sprintf("branch(%s, %s, %s)", v.Condition.String(), v.Then.Label, v.Else.Label)
+	return fmt.Sprintf("branch(%p, %s, %s)", v.Condition, v.Then.Label, v.Else.Label)
 }
\ No newline at end of file
diff --git a/tests/phi-advanced.q b/tests/phi-advanced.q
new file mode 100644
index 0000000..e434cbe
--- /dev/null
+++ b/tests/phi-advanced.q
@@ -0,0 +1,19 @@
+main() {
+	x := 0
+
+	if x == 1 {
+		if x == 0 {
+			x = 2
+		} else {
+			x = 3
+		}
+	} else {
+		if x == 0 {
+			x = 4
+		} else {
+			x = 5
+		}
+	}
+
+	assert x == 4
+}
\ No newline at end of file
diff --git a/tests/else.q b/tests/phi-simple.q
similarity index 72%
rename from tests/else.q
rename to tests/phi-simple.q
index a51edba..829fed8 100644
--- a/tests/else.q
+++ b/tests/phi-simple.q
@@ -1,7 +1,7 @@
 main() {
-	x := 1
+	x := 0
 
-	if x == 0 {
+	if x == 1 {
 		x = 2
 	} else {
 		x = 3
diff --git a/tests/phi.q b/tests/phi.q
index 1e5eaf6..029b339 100644
--- a/tests/phi.q
+++ b/tests/phi.q
@@ -1,9 +1,9 @@
 main() {
-	x := 1
+	x := 0
 
-	if x == 1 {
-		x = 0
+	if x == 0 {
+		x = 1
 	}
 
-	assert x == 0
+	assert x == 1
 }
\ No newline at end of file
diff --git a/tests/tests_test.go b/tests/tests_test.go
index bf36b3f..41fab35 100644
--- a/tests/tests_test.go
+++ b/tests/tests_test.go
@@ -37,9 +37,10 @@ var tests = []run{
 	{"branch-or", "", "", 0},
 	{"branch-both", "", "", 0},
 	{"jump-near", "", "", 0},
-	{"phi", "", "", 0},
-	{"else", "", "", 0},
 	{"switch", "", "", 0},
+	{"phi", "", "", 0},
+	{"phi-simple", "", "", 0},
+	{"phi-advanced", "", "", 0},
 	{"loop", "", "..........", 0},
 	{"loop-lifetime", "", "", 0},
 	{"for", "", "", 0},
-- 
2.51.2