adding OpPhi

src/Runtime.zig

@@ -55,6 +55,9 @@ current_parameter_index: SpvWord,
 current_function: ?*Result,
 function_stack: std.ArrayList(Function),
 
+current_label: ?SpvWord,
+previous_label: ?SpvWord,
+
 specialization_constants: std.AutoHashMapUnmanaged(u32, []const u8),
 
 pub fn init(allocator: std.mem.Allocator, module: *Module) RuntimeError!Self {
@@ -71,6 +74,8 @@ pub fn init(allocator: std.mem.Allocator, module: *Module) RuntimeError!Self {
         .current_parameter_index = 0,
         .current_function = null,
         .function_stack = .empty,
+        .current_label = null,
+        .previous_label = null,
         .specialization_constants = .empty,
     };
 }
@@ -257,4 +262,6 @@ pub fn flushDescriptorSets(self: *const Self, allocator: std.mem.Allocator) Runt
 fn reset(self: *Self) void {
     self.function_stack.clearRetainingCapacity();
     self.current_function = null;
+    self.current_label = null;
+    self.previous_label = null;
 }

src/opcodes.zig

@@ -276,6 +276,7 @@ pub fn initRuntimeDispatcher() void {
     runtime_dispatcher[@intFromEnum(spv.SpvOp.IsNan)]                  = CondEngine(.Float, .IsNan).op;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.IsNormal)]               = CondEngine(.Float, .IsNan).op;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.Kill)]                   = opKill;
+    runtime_dispatcher[@intFromEnum(spv.SpvOp.Label)]                  = opLabel;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.Load)]                   = opLoad;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.LogicalAnd)]             = CondEngine(.Bool, .LogicalAnd).op;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.LogicalEqual)]           = CondEngine(.Bool, .LogicalEqual).op;
@@ -286,6 +287,7 @@ pub fn initRuntimeDispatcher() void {
     runtime_dispatcher[@intFromEnum(spv.SpvOp.MatrixTimesScalar)]      = MathEngine(.Float, .MatrixTimesScalar, false).op; // TODO
     runtime_dispatcher[@intFromEnum(spv.SpvOp.MatrixTimesVector)]      = MathEngine(.Float, .MatrixTimesVector, false).op; // TODO
     runtime_dispatcher[@intFromEnum(spv.SpvOp.Not)]                    = BitEngine(.UInt, .Not).op;
+    runtime_dispatcher[@intFromEnum(spv.SpvOp.Phi)]                    = opPhi;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.Return)]                 = opReturn;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.ReturnValue)]            = opReturnValue;
     runtime_dispatcher[@intFromEnum(spv.SpvOp.SConvert)]               = ConversionEngine(.SInt, .SInt).op;
@@ -1395,6 +1397,7 @@ fn opBitcast(allocator: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeErro
 
 fn opBranch(_: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeError!void {
     const id = try rt.it.next();
+    rt.previous_label = rt.current_label;
     _ = rt.it.jumpToSourceLocation(switch ((try rt.results[id].getVariant()).*) {
         .Label => |l| l.source_location,
         else => return RuntimeError.InvalidSpirV,
@@ -1411,6 +1414,7 @@ fn opBranchConditional(_: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeEr
         .Label => |l| l.source_location,
         else => return RuntimeError.InvalidSpirV,
     };
+    rt.previous_label = rt.current_label;
     if (cond_value.Bool) {
         _ = rt.it.jumpToSourceLocation(true_branch);
     } else {
@@ -2064,11 +2068,14 @@ fn opFunctionParameter(_: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeEr
 
 fn opLabel(_: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeError!void {
     const id = try rt.it.next();
-    rt.results[id].variant = .{
-        .Label = .{
-            .source_location = rt.it.emitSourceLocation() - 2, // Original label location
-        },
-    };
+    rt.current_label = id;
+    if (rt.results[id].variant == null) {
+        rt.results[id].variant = .{
+            .Label = .{
+                .source_location = rt.it.emitSourceLocation() - 2, // Original label location
+            },
+        };
+    }
 }
 
 fn opKill(_: std.mem.Allocator, _: SpvWord, _: *Runtime) RuntimeError!void {
@@ -2126,6 +2133,25 @@ fn opName(allocator: std.mem.Allocator, word_count: SpvWord, rt: *Runtime) Runti
     result.name = try readStringN(allocator, &rt.it, word_count - 1);
 }
 
+fn opPhi(_: std.mem.Allocator, word_count: SpvWord, rt: *Runtime) RuntimeError!void {
+    _ = try rt.it.next(); // result type
+    const id = try rt.it.next();
+
+    const predecessor = rt.previous_label orelse return RuntimeError.InvalidSpirV;
+    const pair_count = @divExact(word_count - 2, 2);
+
+    for (0..pair_count) |_| {
+        const value_id = try rt.it.next();
+        const parent_label_id = try rt.it.next();
+
+        if (parent_label_id == predecessor) {
+            try copyValue(try rt.results[id].getValue(), try rt.results[value_id].getValue());
+            return;
+        }
+    }
+    return RuntimeError.InvalidSpirV;
+}
+
 fn opReturn(_: std.mem.Allocator, _: SpvWord, rt: *Runtime) RuntimeError!void {
     _ = rt.function_stack.pop();
     if (rt.function_stack.getLastOrNull()) |function| {