added lower_nullptr pass

Author: Hugobros3

src/shady/CMakeLists.txt

@@ -70,6 +70,7 @@ set(SHADY_SOURCES
     passes/lower_tailcalls.c
     passes/lower_mask.c
     passes/lower_fill.c
+    passes/lower_nullptr.c
     passes/lower_switch_btree.c
     passes/setup_stack_frames.c
     passes/eliminate_constants.c

src/shady/compile.c

@@ -151,6 +151,7 @@ CompilationResult run_compiler_passes(CompilerConfig* config, Module** pmod) {
     if (config->lower.simt_to_explicit_simd)
         RUN_PASS(simt2d)
     RUN_PASS(lower_fill)
+    RUN_PASS(lower_nullptr)
     RUN_PASS(normalize_builtins)
 
     return CompilationNoError;

src/shady/passes/lower_nullptr.c

@@ -0,0 +1,64 @@
+#include "passes.h"
+
+#include "log.h"
+#include "portability.h"
+#include "dict.h"
+
+#include "../ir_private.h"
+#include "../type.h"
+#include "../rewrite.h"
+#include "../transform/ir_gen_helpers.h"
+
+typedef struct {
+    Rewriter rewriter;
+    struct Dict* map;
+} Context;
+
+static const Node* make_nullptr(Context* ctx, const Type* t) {
+    IrArena* a = ctx->rewriter.dst_arena;
+    const Node** found = find_value_dict(const Type*, const Node*, ctx->map, t);
+    if (found)
+        return *found;
+
+    BodyBuilder* bb = begin_body(a);
+    const Node* nul = gen_reinterpret_cast(bb, t, uint64_literal(a, 0));
+    Node* decl = constant(ctx->rewriter.dst_module, singleton(annotation(a, (Annotation) {
+        .name = "Generated",
+    })), t, format_string_interned(a, "nullptr_%s", name_type_safe(a, t)));
+    decl->payload.constant.instruction = yield_values_and_wrap_in_block(bb, singleton(nul));
+    const Node* ref = ref_decl_helper(a, decl);
+    insert_dict(const Type*, const Node*, ctx->map, t, ref);
+    return ref;
+}
+
+static const Node* process(Context* ctx, const Node* node) {
+    IrArena* a = ctx->rewriter.dst_arena;
+    Rewriter* r = &ctx->rewriter;
+    switch (node->tag) {
+        case NullPtr_TAG: {
+            const Type* t = rewrite_node(r, node->payload.null_ptr.ptr_type);
+            assert(t->tag == PtrType_TAG);
+            return make_nullptr(ctx, t);
+        }
+        default: break;
+    }
+
+    return recreate_node_identity(&ctx->rewriter, node);
+}
+
+KeyHash hash_node(Node**);
+bool compare_node(Node**, Node**);
+
+Module* lower_nullptr(SHADY_UNUSED const CompilerConfig* config, Module* src) {
+    ArenaConfig aconfig = get_arena_config(get_module_arena(src));
+    IrArena* a = new_ir_arena(aconfig);
+    Module* dst = new_module(a, get_module_name(src));
+    Context ctx = {
+        .rewriter = create_rewriter(src, dst, (RewriteNodeFn) process),
+        .map = new_dict(const Node*, Node*, (HashFn) hash_node, (CmpFn) compare_node),
+    };
+    rewrite_module(&ctx.rewriter);
+    destroy_rewriter(&ctx.rewriter);
+    destroy_dict(ctx.map);
+    return dst;
+}

src/shady/passes/passes.h

@@ -98,6 +98,7 @@ RewritePass lower_int;
 RewritePass lower_vec_arr;
 RewritePass lower_workgroups;
 RewritePass lower_fill;
+RewritePass lower_nullptr;
 
 /// @}