1 files changed, 48 insertions, 3 deletions

diff --git a/src/codegen.cpp b/src/codegen.cpp
index edc2c7f435..1455b4b743 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -941,6 +941,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
             return buf_create_from_str("async function called with noasync suspended");
         case PanicMsgIdResumeNotSuspendedFn:
             return buf_create_from_str("resumed a non-suspended function");
+        case PanicMsgIdBadSentinel:
+            return buf_create_from_str("sentinel mismatch");
     }
     zig_unreachable();
 }
@@ -1419,6 +1421,27 @@ static void add_bounds_check(CodeGen *g, LLVMValueRef target_val,
     LLVMPositionBuilderAtEnd(g->builder, ok_block);
 }
 
+static void add_sentinel_check(CodeGen *g, LLVMValueRef sentinel_elem_ptr, ZigValue *sentinel) {
+    LLVMValueRef expected_sentinel = gen_const_val(g, sentinel, "");
+
+    LLVMValueRef actual_sentinel = gen_load_untyped(g, sentinel_elem_ptr, 0, false, "");
+    LLVMValueRef ok_bit;
+    if (sentinel->type->id == ZigTypeIdFloat) {
+        ok_bit = LLVMBuildFCmp(g->builder, LLVMRealOEQ, actual_sentinel, expected_sentinel, "");
+    } else {
+        ok_bit = LLVMBuildICmp(g->builder, LLVMIntEQ, actual_sentinel, expected_sentinel, "");
+    }
+
+    LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "SentinelFail");
+    LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "SentinelOk");
+    LLVMBuildCondBr(g->builder, ok_bit, ok_block, fail_block);
+
+    LLVMPositionBuilderAtEnd(g->builder, fail_block);
+    gen_safety_crash(g, PanicMsgIdBadSentinel);
+
+    LLVMPositionBuilderAtEnd(g->builder, ok_block);
+}
+
 static LLVMValueRef gen_assert_zero(CodeGen *g, LLVMValueRef expr_val, ZigType *int_type) {
     LLVMValueRef zero = LLVMConstNull(get_llvm_type(g, int_type));
     LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntEQ, expr_val, zero, "");
@@ -5244,6 +5267,9 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
 
     bool want_runtime_safety = instruction->safety_check_on && ir_want_runtime_safety(g, &instruction->base);
 
+    ZigType *res_slice_ptr_type = instruction->base.value->type->data.structure.fields[slice_ptr_index]->type_entry;
+    ZigValue *sentinel = res_slice_ptr_type->data.pointer.sentinel;
+
     if (array_type->id == ZigTypeIdArray ||
         (array_type->id == ZigTypeIdPointer && array_type->data.pointer.ptr_len == PtrLenSingle))
     {
@@ -5265,6 +5291,15 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
                 LLVMValueRef array_end = LLVMConstInt(g->builtin_types.entry_usize->llvm_type,
                         array_type->data.array.len, false);
                 add_bounds_check(g, end_val, LLVMIntEQ, nullptr, LLVMIntULE, array_end);
+
+                if (sentinel != nullptr) {
+                    LLVMValueRef indices[] = {
+                        LLVMConstNull(g->builtin_types.entry_usize->llvm_type),
+                        end_val,
+                    };
+                    LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, array_ptr, indices, 2, "");
+                    add_sentinel_check(g, sentinel_elem_ptr, sentinel);
+                }
             }
         }
         if (!type_has_bits(array_type)) {
@@ -5297,6 +5332,10 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
 
         if (want_runtime_safety) {
             add_bounds_check(g, start_val, LLVMIntEQ, nullptr, LLVMIntULE, end_val);
+            if (sentinel != nullptr) {
+                LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, array_ptr, &end_val, 1, "");
+                add_sentinel_check(g, sentinel_elem_ptr, sentinel);
+            }
         }
 
         if (type_has_bits(array_type)) {
@@ -5337,18 +5376,24 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
             end_val = prev_end;
         }
 
+        LLVMValueRef src_ptr_ptr = LLVMBuildStructGEP(g->builder, array_ptr, (unsigned)ptr_index, "");
+        LLVMValueRef src_ptr = gen_load_untyped(g, src_ptr_ptr, 0, false, "");
+
         if (want_runtime_safety) {
             assert(prev_end);
             add_bounds_check(g, start_val, LLVMIntEQ, nullptr, LLVMIntULE, end_val);
             if (instruction->end) {
                 add_bounds_check(g, end_val, LLVMIntEQ, nullptr, LLVMIntULE, prev_end);
+
+                if (sentinel != nullptr) {
+                    LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &end_val, 1, "");
+                    add_sentinel_check(g, sentinel_elem_ptr, sentinel);
+                }
             }
         }
 
-        LLVMValueRef src_ptr_ptr = LLVMBuildStructGEP(g->builder, array_ptr, (unsigned)ptr_index, "");
-        LLVMValueRef src_ptr = gen_load_untyped(g, src_ptr_ptr, 0, false, "");
         LLVMValueRef ptr_field_ptr = LLVMBuildStructGEP(g->builder, tmp_struct_ptr, (unsigned)ptr_index, "");
-        LLVMValueRef slice_start_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &start_val, (unsigned)len_index, "");
+        LLVMValueRef slice_start_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &start_val, 1, "");
         gen_store_untyped(g, slice_start_ptr, ptr_field_ptr, 0, false);
 
         LLVMValueRef len_field_ptr = LLVMBuildStructGEP(g->builder, tmp_struct_ptr, (unsigned)len_index, "");