stage2: elemPtr for slices

* Restructure elemPtr a bit
* New AIR instruction: slice_elem_ptr, which returns a pointer to an element of a slice
* Value: adapt elemPtr to work on slices

1 files changed, 19 insertions, 0 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index f09bb574af..9050499fce 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -1083,6 +1083,7 @@ fn genBody(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail, OutO
             .ptr_elem_val       => try airPtrElemVal(f, inst, "["),
             .ptr_elem_ptr       => try airPtrElemPtr(f, inst),
             .slice_elem_val     => try airSliceElemVal(f, inst, "["),
+            .slice_elem_ptr     => try airSliceElemPtr(f, inst),
             .array_elem_val     => try airArrayElemVal(f, inst),
 
             .unwrap_errunion_payload     => try airUnwrapErrUnionPay(f, inst),
@@ -1165,6 +1166,24 @@ fn airSliceElemVal(f: *Function, inst: Air.Inst.Index, prefix: []const u8) !CVal
     return local;
 }
 
+fn airSliceElemPtr(f: *Function, inst: Air.Inst.Index) !CValue {
+    if (f.liveness.isUnused(inst))
+        return CValue.none;
+    const ty_pl = f.air.instructions.items(.data)[inst].ty_pl;
+    const bin_op = f.air.extraData(Air.Bin, ty_pl.payload).data;
+
+    const slice = try f.resolveInst(bin_op.lhs);
+    const index = try f.resolveInst(bin_op.rhs);
+    const writer = f.object.writer();
+    const local = try f.allocLocal(f.air.typeOfIndex(inst), .Const);
+    try writer.writeAll(" = &");
+    try f.writeCValue(writer, slice);
+    try writer.writeByte('[');
+    try f.writeCValue(writer, index);
+    try writer.writeAll("];\n");
+    return local;
+}
+
 fn airArrayElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
     if (f.liveness.isUnused(inst)) return CValue.none;