packed structs support comptime bitcasting

 * `type_size_store` is no longer a thing. loading and storing a pointer
   to a value may dereference up to `@sizeOf(T)` bytes, even for
   integers such as `u24`.
 * fix `types_have_same_zig_comptime_repr` to not think that the
   same `ZigTypeId` means the `ConstExprValue` neccesarily has the
   same representation.
 * implement `buf_write_value_bytes` and `buf_read_value_bytes` for
   `ContainerLayoutPacked`

closes #1120

1 files changed, 4 insertions, 1 deletions

diff --git a/src/codegen.cpp b/src/codegen.cpp
index 86923a0bde..dbe0291299 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -3070,7 +3070,10 @@ static LLVMValueRef ir_render_bit_cast(CodeGen *g, IrExecutable *executable,
 {
     ZigType *wanted_type = instruction->base.value.type;
     LLVMValueRef value = ir_llvm_value(g, instruction->value);
-    return LLVMBuildBitCast(g->builder, value, wanted_type->type_ref, "");
+    // We either bitcast the value directly or bitcast the pointer which does a pointer cast
+    LLVMTypeRef wanted_type_ref = handle_is_ptr(wanted_type) ?
+        LLVMPointerType(wanted_type->type_ref, 0) : wanted_type->type_ref;
+    return LLVMBuildBitCast(g->builder, value, wanted_type_ref, "");
 }
 
 static LLVMValueRef ir_render_widen_or_shorten(CodeGen *g, IrExecutable *executable,