selfpatch-slr/playground/spslr_pinpoint.cpp

#include <iostream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <list>

#include <gcc-plugin.h>
#include <plugin-version.h>
#include <tree.h>
#include <langhooks.h>
#include <gimple.h>
#include <gimplify.h>
#include <stringpool.h>
#include <tree-pass.h>
#include <gimple-iterator.h>
#include <gimple-pretty-print.h>
#include <tree-pretty-print.h>
#include <tree-dump.h>
#include <print-tree.h>
#include <tree-iterator.h>
#include <rtl.h>
#include <memmodel.h>
#include <emit-rtl.h>
#include <df.h>

int plugin_is_GPL_compatible;

#ifndef SPSLR_OFFSETOF
#define SPSLR_OFFSETOF "__spslr_offsetof_" /* with suffix <uid> */
#endif

#ifndef UNSPEC_SPSLR_OFFSETOF
#define UNSPEC_SPSLR_OFFSETOF 1042
#endif

// Recognize __attribute__((spslr)) on structures and track their layout

struct Member {
	using OFF = unsigned long;
	using SIZE = unsigned long;

	static constexpr int FLAG_DANGERZONE = 1;

	OFF offset = 0;
	SIZE size = 0;
	int flags = 0;
};

struct Target {
	using UID = unsigned long;

	UID uid;
	std::map<Member::OFF, Member> members;

	void log_member(const Member& member);
	const Member* get_member(Member::OFF offset) const;
};

struct TargetTree {
	tree t;
	Target::UID uid;
};

static Target::UID next_target_uid = 0;
static std::unordered_map<Target::UID, Target> targets;
static std::list<TargetTree> target_trees;

static std::unordered_set<tree> target_markings;

static bool find_target_log(tree t, Target::UID& uid) {
	for (const TargetTree& tt : target_trees) {
		if (lang_hooks.types_compatible_p(tt.t, t)) {
			uid = tt.uid;
			return true;
		}
	}

	return false;
}

void Target::log_member(const Member& member) {
	Member tmp_member;
	tmp_member.offset = member.offset;
	tmp_member.size = (member.size == 0 ? 1 : member.size);
	tmp_member.flags = (member.size == 0 ? Member::FLAG_DANGERZONE : 0) | member.flags;

	// Overlaps are dangerous -> remove and integrate into member
	auto overlap_end = members.lower_bound(tmp_member.offset + tmp_member.size);
	for (auto it = std::make_reverse_iterator(overlap_end); it != members.rend();) {
		const Member& existing_member = it->second;

		if (existing_member.offset + existing_member.size <= tmp_member.offset)
			break;

		Member::OFF combined_end = std::max<Member::OFF>(tmp_member.offset + tmp_member.size,
			existing_member.offset + existing_member.size);

		Member::OFF combined_offset = std::min<Member::OFF>(tmp_member.offset, existing_member.offset);
		Member::SIZE combined_size = combined_end - combined_offset;

		tmp_member.flags |= (existing_member.flags | Member::FLAG_DANGERZONE);
		tmp_member.offset = combined_offset;
		tmp_member.size = combined_size;

		// Erase overlapping member
		auto tmp_forward = std::prev(it.base());
		tmp_forward = members.erase(tmp_forward);
		it = std::make_reverse_iterator(tmp_forward);
	}

	members.emplace(tmp_member.offset, tmp_member);
}

const Member* Target::get_member(Member::OFF offset) const {
	auto it = members.find(offset);
	if (it == members.end())
		return nullptr;

	return &it->second;
}

static void log_target(tree node) {
	node = TYPE_MAIN_VARIANT(node);
	if (!node)
		return;

	if (TREE_CODE(node) != RECORD_TYPE)
		return;

	auto marking = target_markings.find(node);
	if (marking == target_markings.end())
		return;

	Target::UID existing_target;
	if (find_target_log(node, existing_target))
		return;

	Target::UID tuid = next_target_uid++;

	TargetTree new_tt;
	new_tt.t = node;
	new_tt.uid = tuid;

	target_trees.push_back(new_tt);
	targets.emplace(tuid, Target{});

	Target& target = targets.at(tuid);
	target.uid = tuid;

	// Log all members
	for (tree field = TYPE_FIELDS(node); field; field = DECL_CHAIN(field)) {
		if (TREE_CODE(field) != FIELD_DECL)
			continue;

		HOST_WIDE_INT field_byte_offset = 0;
		if (TREE_CODE(DECL_FIELD_OFFSET(field)) == INTEGER_CST)
			field_byte_offset = tree_to_uhwi(DECL_FIELD_OFFSET(field));

		HOST_WIDE_INT field_bit_offset = 0;
		if (TREE_CODE(DECL_FIELD_BIT_OFFSET(field)) == INTEGER_CST)
			field_bit_offset = tree_to_uhwi(DECL_FIELD_BIT_OFFSET(field));

		HOST_WIDE_INT field_bit_offset_bytes = field_bit_offset / 8;
		field_byte_offset += field_bit_offset_bytes;
		field_bit_offset -= field_bit_offset_bytes * 8;

		HOST_WIDE_INT field_bit_size = 0;
		if (TREE_CODE(DECL_SIZE(field)) == INTEGER_CST)
			field_bit_size = tree_to_uhwi(DECL_SIZE(field));

		bool is_bitfield = (DECL_BIT_FIELD_TYPE(field) != NULL_TREE);
		bool is_multibyte = (field_bit_size % 8 == 0 && field_bit_offset == 0);
		bool is_dangerous = (is_bitfield || !is_multibyte);

		HOST_WIDE_INT field_offset_bit_size = field_bit_offset + field_bit_size;
		HOST_WIDE_INT effective_field_size = field_offset_bit_size / 8;
		if (field_offset_bit_size % 8 != 0)
			effective_field_size += 1;

		Member member;
		member.offset = (Member::OFF)field_byte_offset;
		member.size = (Member::SIZE)effective_field_size;
		member.flags = (is_dangerous ? Member::FLAG_DANGERZONE : 0);

		target.log_member(member);
	}
}

static tree log_target_attribute(tree* node, tree name, tree args, int flags, bool* no_add_attrs) {
	if (!node)
		return NULL_TREE;

	if (TREE_CODE(*node) != RECORD_TYPE)
		return NULL_TREE;

	tree type_main_variant = TYPE_MAIN_VARIANT(*node);
	if (!type_main_variant)
		return NULL_TREE;

	target_markings.insert(type_main_variant);
	return NULL_TREE;
}

static struct attribute_spec spslr_attribute = {
	"spslr", 0, 0, false, false, false, false, log_target_attribute, NULL
};

void on_register_attributes(void* event_data, void* data) {
	register_attribute(&spslr_attribute);
}

static void on_type_complete(void* event_data, void* user_data) {
	tree type = (tree)event_data;
	log_target(type);
}

// Early hook to make COMPONENT_REF nodes survice front end

struct SPSLROffsetofCallData {
	using UID = unsigned long;

	UID uid;
	Target::UID target;
	Member::OFF member;
};

static SPSLROffsetofCallData::UID spslr_offsetof_next_uid = 0;
static std::unordered_map<SPSLROffsetofCallData::UID, SPSLROffsetofCallData> spslr_offsetof_calls;

static tree make_spslr_offsetof_decl(SPSLROffsetofCallData::UID uid) {
	tree fntype = build_function_type(sizetype, NULL_TREE);

	char fnname[128];
	snprintf(fnname, sizeof(fnname), "%s%lu", SPSLR_OFFSETOF, uid);

	tree fnname_tree = get_identifier(fnname);
	if (!fnname_tree)
		return NULL_TREE;

	tree fndecl = build_fn_decl(IDENTIFIER_POINTER(fnname_tree), fntype);
	if (!fndecl)
		return NULL_TREE;

	DECL_EXTERNAL(fndecl) = 1;
	TREE_PUBLIC(fndecl) = 1;
	DECL_ARTIFICIAL(fndecl) = 1;

	// Prevent VOP problems later when removing calls
	// Explanation -> VOPs mark memory side-effects, which these calls have none of anyways
	DECL_PURE_P(fndecl) = 1;
	DECL_IS_NOVOPS(fndecl) = 1;

	return fndecl;
}

static bool is_relevant_offsetof(tree ref, Target::UID& tuid, Member::OFF& moff) {
	if (!ref || TREE_CODE(ref) != COMPONENT_REF)
		return false;

	tree base = TREE_OPERAND(ref, 0);
	if (!base)
		return false;

	tree base_type = TREE_TYPE(base);
	if (!base_type)
		return false;

	if (!find_target_log(base_type, tuid))
		return false;

	auto target_it = targets.find(tuid);
	if (target_it == targets.end())
		return false;

	const Target& t = target_it->second;

	tree field = TREE_OPERAND(ref, 1);

	HOST_WIDE_INT field_byte_offset = 0;
	if (TREE_CODE(DECL_FIELD_OFFSET(field)) == INTEGER_CST)
		field_byte_offset = tree_to_uhwi(DECL_FIELD_OFFSET(field));

	HOST_WIDE_INT field_bit_offset = 0;
	if (TREE_CODE(DECL_FIELD_BIT_OFFSET(field)) == INTEGER_CST)
		field_bit_offset = tree_to_uhwi(DECL_FIELD_BIT_OFFSET(field));

	Member::OFF effective_field_offset = (field_byte_offset + (field_bit_offset / 8));
	moff = effective_field_offset;

	const Member* m = t.get_member(effective_field_offset);
	if (!m)
		return false;

	return !(m->flags & Member::FLAG_DANGERZONE);
}

static tree instrument_offsetof_maybe(tree ref) {
	SPSLROffsetofCallData call_data;
	if (!is_relevant_offsetof(ref, call_data.target, call_data.member))
		return NULL_TREE;

	location_t loc = EXPR_LOCATION(ref);
	tree result_type = TREE_TYPE(ref);

	call_data.uid = spslr_offsetof_next_uid++;

	tree spslr_offsetof_decl = NULL_TREE;
	if (!(spslr_offsetof_decl = make_spslr_offsetof_decl(call_data.uid))) {
		std::cerr << "spslr_pinpoint -> failed to instrument COMPONENT_REF (" << SPSLR_OFFSETOF << "<uid> unavailable)" << std::endl;
		return NULL_TREE;
	}

	spslr_offsetof_calls.emplace(call_data.uid, call_data);
	tree call_tree = build_call_expr_loc(loc, spslr_offsetof_decl, 0);

	// Get base as char*
	tree base = TREE_OPERAND(ref, 0);
	tree base_addr;

	if (TREE_CODE(base) == ADDR_EXPR) {
		// base_addr = base;
		std::cerr << "spslr_pinpoint -> unexpected ADDR_EXPR as COMPONENT_REF base!" << std::endl;
		return NULL_TREE;
	} else {
		base_addr = build_fold_addr_expr(base);
	}

	tree char_ptr_type = build_pointer_type(char_type_node);
	tree base_char_ptr = fold_convert(char_ptr_type, base_addr);

	// Add __spslr_offsetof, cast back to field pointer, then dereference
	tree plus = build2_loc(loc, POINTER_PLUS_EXPR, char_ptr_type, base_char_ptr, call_tree);

	tree field_ptr_type = build_pointer_type(result_type);
	tree cast_back = build1_loc(loc, NOP_EXPR, field_ptr_type, plus);

	tree new_ref = build1_loc(loc, INDIRECT_REF, result_type, cast_back);

	return new_ref;
}

static void on_build_component_ref(void* event_data, void* user_data) {
	tree* component_ref_node = (tree*)event_data;
	if (!component_ref_node)
		return;

	tree repl = instrument_offsetof_maybe(*component_ref_node);
	if (repl)
		*component_ref_node = repl;
}

// Identify any missing COMPONENT_REFs (e.g. from CONSTRUCTOR trees)

static const pass_data log_component_refs_pass_data = {
	GIMPLE_PASS,
	"log_component_refs",
	OPTGROUP_NONE,
	TV_NONE,
	0,0,0,0,
	TODO_update_ssa
};

struct log_component_refs_pass : gimple_opt_pass {
	log_component_refs_pass(gcc::context *ctxt);
	unsigned int execute(function* fun) override;
};

log_component_refs_pass::log_component_refs_pass(gcc::context *ctxt) : gimple_opt_pass(log_component_refs_pass_data, ctxt) {}

struct GCRChain {
	struct Link {
		tree t = NULL_TREE;
		bool relevant = false;
		SPSLROffsetofCallData call_data;
	};

	bool relevant = false;
	std::list<Link> links;
	tree base = NULL_TREE;
};

static tree walk_tree_contains_component_ref(tree* tp, int* walk_subtrees, void* data) {
	int* found_flag = (int*)data;

	if (!tp || !*tp)
		return NULL_TREE;

	if (TREE_CODE(*tp) == COMPONENT_REF)
		*found_flag = 1;

	return NULL_TREE;
}

static bool contains_component_ref(tree ref) {
	int found_flag = 0;
	walk_tree(&ref, walk_tree_contains_component_ref, &found_flag, NULL);
	return found_flag != 0;
}

static bool gimple_component_ref_chain(tree ref, GCRChain& chain) {
	if (!ref)
		return false;

	if (TREE_CODE(ref) != COMPONENT_REF) {
		if (chain.links.empty())
			return false;

		if (contains_component_ref(ref))
			return false;

		chain.base = ref;
		return true;
	}

	GCRChain::Link link;
	link.t = ref;
	link.relevant = is_relevant_offsetof(ref, link.call_data.target, link.call_data.member);

	if (link.relevant) {
		link.call_data.uid = spslr_offsetof_next_uid++;
		chain.relevant = true;
	}

	chain.links.push_front(link);
	return gimple_component_ref_chain(TREE_OPERAND(ref, 0), chain);
}

static HOST_WIDE_INT get_field_offset_bits(tree field)
{
    gcc_assert(TREE_CODE(field) == FIELD_DECL);

    // Get the offset expression (may not be a constant early in compilation)
    tree offset_tree = DECL_FIELD_OFFSET(field);
    HOST_WIDE_INT bitpos_within_unit = tree_to_uhwi(DECL_FIELD_BIT_OFFSET(field));

    // Convert the byte offset to bits
    HOST_WIDE_INT bit_offset = bitpos_within_unit;
    if (offset_tree && TREE_CODE(offset_tree) == INTEGER_CST)
        bit_offset += tree_to_shwi(offset_tree) * BITS_PER_UNIT;

    return bit_offset;
}

static bool get_field_offset(tree field, Member::OFF& off) {
	if (!field || TREE_CODE(field) != FIELD_DECL)
		return false;

	if (DECL_BIT_FIELD(field))
		return false;

	tree byte_offset_tree = DECL_FIELD_OFFSET(field);
	tree bit_offset_tree = DECL_FIELD_BIT_OFFSET(field);

	if (!byte_offset_tree || !bit_offset_tree)
		return false;

	if (TREE_CODE(byte_offset_tree) != INTEGER_CST || TREE_CODE(bit_offset_tree) != INTEGER_CST)
		return false;

	HOST_WIDE_INT byte_offset = tree_to_uhwi(byte_offset_tree);
	HOST_WIDE_INT bit_offset = tree_to_uhwi(bit_offset_tree);

	if (bit_offset % 8 != 0)
		return false;

	off = (Member::OFF)byte_offset + (Member::OFF)bit_offset / 8;
	return true;
}

static tree gimple_instrument_offsetof_maybe(tree ref, gimple_stmt_iterator* gsi) {
	GCRChain gcrc;
	if (!gimple_component_ref_chain(ref, gcrc)) {
		std::cerr << "spslr_pinpoint -> failed to parse COMPONENT_REF chain" << std::endl;
		return NULL_TREE;
	}

	if (!gcrc.relevant)
		return NULL_TREE;

	// Store base pointer in a temporary variable (as char*)

	tree char_ptr_type = build_pointer_type(char_type_node);
	tree base_tmp = NULL_TREE;
	{
		tree base_ptr;

		if (TREE_CODE(gcrc.base) == ADDR_EXPR) {
			std::cerr << "spslr_pinpoint -> unexpected ADDR_EXPR as COMPONENT_REF base!" << std::endl;
			return NULL_TREE;
		} else {
			base_ptr = build_fold_addr_expr(gcrc.base);
		}

		tree base_char_ptr = fold_convert(char_ptr_type, base_ptr);
		base_tmp = create_tmp_var(char_ptr_type, NULL);

		gimple* base_tmp_assignment = gimple_build_assign(base_tmp, base_char_ptr);
		gsi_insert_before(gsi, base_tmp_assignment, GSI_SAME_STMT);
	}

	// For each component ref in chain, add the member offset to the pointer

	for (const GCRChain::Link& cr : gcrc.links) {
		// NOTE -> Could fold into single call here (needs to track what offsets contribute, +irrelevant combined)
		if (cr.relevant) {
			// Add offsetof call
			tree spslr_offsetof_decl = NULL_TREE;
			if (!(spslr_offsetof_decl = make_spslr_offsetof_decl(cr.call_data.uid))) {
				std::cerr << "spslr_pinpoint -> failed to instrument COMPONENT_REF ("
					<< SPSLR_OFFSETOF << "<uid> unavailable)" << std::endl;
				return NULL_TREE;
			}

			spslr_offsetof_calls.emplace(cr.call_data.uid, cr.call_data);

			// Call to __spslr_offsetof is a separate statement
			gimple* call_stmt = gimple_build_call(spslr_offsetof_decl, 0);
			tree offset_tmp = create_tmp_var(size_type_node, NULL);
			gimple_call_set_lhs(call_stmt, offset_tmp);
			gsi_insert_before(gsi, call_stmt, GSI_SAME_STMT);

			// Add call return value to current base pointer
			tree addition = build2(POINTER_PLUS_EXPR, char_ptr_type, base_tmp, offset_tmp);
			base_tmp = create_tmp_var(char_ptr_type, NULL);
			gimple* addition_assignment = gimple_build_assign(base_tmp, addition);
			gsi_insert_before(gsi, addition_assignment, GSI_SAME_STMT);
		} else {
			// Add offsetof contant
			tree field = TREE_OPERAND(cr.t, 1);

			Member::OFF offset = 0;
			if (!get_field_offset(field, offset)) {
				std::cerr << "spslr_pinpoint -> failed to get offset of an irrelevant member "
					<< "in a relevant COMPONENT_REF chain" << std::endl;
				return NULL_TREE;
			}

			// Add constant offset to current base pointer
			tree addition = build2(POINTER_PLUS_EXPR, char_ptr_type, base_tmp, build_int_cst(sizetype, offset));
			base_tmp = create_tmp_var(char_ptr_type, NULL);
			gimple* addition_assignment = gimple_build_assign(base_tmp, addition);
			gsi_insert_before(gsi, addition_assignment, GSI_SAME_STMT);
		}
	}

	// Cast char pointer back to field pointer and dereference

	tree field_ptr_type = build_pointer_type(TREE_TYPE(ref));

	tree field_ptr = fold_convert(field_ptr_type, base_tmp);
	tree field_ptr_tmp = create_tmp_var(field_ptr_type, NULL);
	gimple* field_ptr_tmp_assignment = gimple_build_assign(field_ptr_tmp, field_ptr);
	gsi_insert_before(gsi, field_ptr_tmp_assignment, GSI_SAME_STMT);

	tree offset0 = fold_convert(field_ptr_type, build_int_cst(sizetype, 0));
	tree result_ref = build2(MEM_REF, TREE_TYPE(ref), field_ptr_tmp, offset0);

	return result_ref;
}

static void instrument_tree(const std::list<tree*>& path, gimple_stmt_iterator* gsi, unsigned& cancel_levels) {
	if (path.empty() || !gsi)
		return;

	tree ref = *path.back();
	if (!ref || TREE_CODE(ref) != COMPONENT_REF)
		return;

	cancel_levels = 1;

	tree instrumented_ref = gimple_instrument_offsetof_maybe(ref, gsi);
	if (!instrumented_ref)
		return;

	gimple_set_modified(gsi_stmt(*gsi), true);
	*path.back() = instrumented_ref;

	// At this point, instrumented_ref is a MEM_REF node (off=0). A wrapping ADDR_EXPR cancels it out.

	if (path.size() < 2)
		return;

	tree* parent = *(++path.rbegin());

	if (TREE_CODE(*parent) == ADDR_EXPR) {
		// Note -> the base of the MEM_REF is expected to have the same type as the ADDR_EXPR
		*parent = TREE_OPERAND(instrumented_ref, 0);
		cancel_levels++;
	}
}

struct TreeWalkData {
	std::list<tree*> path;
	gimple_stmt_iterator* gsi;
	unsigned cancel_levels;
};

static tree walk_tree_level(tree* tp, int* walk_subtrees, void* data) {
	TreeWalkData* twd = (TreeWalkData*)data;
	if (!twd)
		return NULL_TREE;

	if (!twd->path.empty() && twd->path.back() == tp)
		return NULL_TREE; // root of this level

	if (walk_subtrees)
		*walk_subtrees = 0;

	twd->cancel_levels = 0;
	twd->path.push_back(tp);

	instrument_tree(twd->path, twd->gsi, twd->cancel_levels);

	if (twd->cancel_levels == 0)
		walk_tree(tp, walk_tree_level, data, NULL);

	twd->path.pop_back();

	if (twd->cancel_levels > 0)
		twd->cancel_levels--;

	// Cancel current level if there are still cancel_levels due
	return twd->cancel_levels == 0 ? NULL_TREE : *tp;
}

static bool walk_gimple_stmt(gimple_stmt_iterator* gsi) {
	if (!gsi || gsi_end_p(*gsi))
		return false;

	gimple* stmt = gsi_stmt(*gsi);

	for (int i = 0; i < gimple_num_ops(stmt); i++) {
		tree* op = gimple_op_ptr(stmt, i);
		if (!op || !*op)
			continue;

		TreeWalkData twd;
		twd.gsi = gsi;

		walk_tree_level(op, NULL, &twd);
	}

	return true;
}

unsigned int log_component_refs_pass::execute(function* fun) {
	const char* funcname = fun->decl && DECL_NAME(fun->decl)
		? IDENTIFIER_POINTER(DECL_NAME(fun->decl))
		: "<anonymous>";

	tree fndecl = fun->decl;
	if (!fndecl)
		return 0;

	gimple_seq body = gimple_body(fndecl);
	for (gimple_stmt_iterator gsi = gsi_start(body); walk_gimple_stmt(&gsi); gsi_next(&gsi));

	// print_gimple_seq(stderr, gimple_body(fun->decl), 0, TDF_NONE);
	return 0;
}

// Gimple print pass for debugging

static const pass_data print_pass_data = {
	GIMPLE_PASS,
	"gimple_print",
	OPTGROUP_NONE,
	TV_NONE,
	0,0,0,0, 0
};

struct print_pass : gimple_opt_pass {
	print_pass(gcc::context *ctxt);
	unsigned int execute(function* fun) override;
};

print_pass::print_pass(gcc::context *ctxt) : gimple_opt_pass(print_pass_data, ctxt) {}

unsigned int print_pass::execute(function* fun) {
	const char* funcname = fun->decl && DECL_NAME(fun->decl)
		? IDENTIFIER_POINTER(DECL_NAME(fun->decl))
		: "<anonymous>";

	fprintf(stderr, "[spslr_pinpoint] Function: %s\n", funcname);
	basic_block bb;
	FOR_EACH_BB_FN(bb, fun) {
		for (gimple_stmt_iterator gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
			gimple* stmt = gsi_stmt(gsi);
			print_gimple_stmt(stderr, stmt, 0, TDF_SLIM);
		}
	}
	fprintf(stderr, "\n");

	return 0;
}

// At early RTL, replace __spslr_offsetof_<uid> with UNSPECs to avoid ABI and clobbering "problems"

static bool extract_callee_symbol (rtx call_rtx, const char** out_name) {
	if (!call_rtx || GET_CODE(call_rtx) != CALL)
		return false;

	rtx op0 = XEXP(call_rtx, 0);
	if (!op0)
		return false;

	rtx addr = XEXP(op0, 0);
	if (addr && GET_CODE(addr) == SYMBOL_REF) {
		*out_name = XSTR(addr, 0);
		return true;
	}

	return false;
}

static bool parse_uid_from_name(const char* name, unsigned long* out_uid) {
	if (!name || !out_uid)
		return false;

	if (strncmp(name, SPSLR_OFFSETOF, strlen(SPSLR_OFFSETOF)) != 0)
		return false;

	const char *p = name + strlen(SPSLR_OFFSETOF);
	if (*p == 0)
		return false;

	char *endp = nullptr;
	unsigned long v = strtoul(p, &endp, 10);
	if (endp == p)
		return false;

	*out_uid = v;
	return true;
}

static bool extract_dest_and_call (rtx pat, rtx* out_dest, rtx* out_call) {
	if (!pat)
		return false;

	if (GET_CODE(pat) == SET) {
		rtx src = SET_SRC(pat);
		if (GET_CODE(src) == CALL) {
			*out_dest = SET_DEST(pat);
			*out_call = src;
			return true;
		}
		return false;
	}

	if (GET_CODE(pat) == PARALLEL) {
		// Look for a SET whose src is CALL
		int n = XVECLEN(pat, 0);
		for (int i = 0; i < n; ++i) {
			rtx elt = XVECEXP(pat, 0, i);
			if (GET_CODE(elt) == SET && GET_CODE(SET_SRC(elt)) == CALL) {
				*out_dest = SET_DEST(elt);
				*out_call = SET_SRC(elt);
				return true;
			}
		}
	}

	return false;
}

static void call_to_unspec(function* fn) {
	if (!fn)
		return;

	unsigned replaced = 0;

	basic_block bb;
	FOR_EACH_BB_FN(bb, fn) {
		for (rtx_insn* insn = BB_HEAD(bb); insn != NEXT_INSN(BB_END(bb)); insn = NEXT_INSN(insn)) {
			if (!INSN_P(insn) || !CALL_P(insn))
				continue;

			rtx pat = PATTERN(insn);
			rtx dest = NULL_RTX;
			rtx call = NULL_RTX;
			if (!extract_dest_and_call(pat, &dest, &call))
				continue;

			const char *name = nullptr;
			if (!extract_callee_symbol(call, &name))
				continue;

			unsigned long uid = 0;
			if (!parse_uid_from_name(name, &uid))
				continue;

			// We expect a returning call (assigned to dest)
			if (!dest || !REG_P(dest) || GET_MODE(dest) == VOIDmode)
				continue;

			machine_mode mode = GET_MODE(dest);

			// Build: (set dest (unspec:mode [(const_int uid)] UNSPEC_SPSLR_OFFSETOF))
			rtvec vec = gen_rtvec(1, GEN_INT((HOST_WIDE_INT) uid));
			rtx uns = gen_rtx_UNSPEC(mode, vec, UNSPEC_SPSLR_OFFSETOF); // Note -> maybe volatile
			rtx set = gen_rtx_SET(dest, uns);

			emit_insn_before(set, insn);
			delete_insn(insn);
			replaced++;
		}
	}

	if (replaced) {
		df_set_bb_dirty(ENTRY_BLOCK_PTR_FOR_FN(fn));
		df_set_bb_dirty(EXIT_BLOCK_PTR_FOR_FN(fn));
	}
}

const pass_data call_to_unspec_pass_data = {
	RTL_PASS,
	"call_to_unspec",
	OPTGROUP_NONE,
	TV_NONE,
	PROP_rtl,
	0, 0, 0, 0
};

struct call_to_unspec_pass : rtl_opt_pass {
	call_to_unspec_pass(gcc::context* ctxt)
		: rtl_opt_pass(call_to_unspec_pass_data, ctxt) {}

	unsigned int execute(function* fn) override {
		call_to_unspec(fn);
		return 0;
	}
};

// Late RTL pass replaces UNSPECs with labeled constants (must happen before vregs, no optimizations afterwards)

static bool lookup_initial_member_offset(SPSLROffsetofCallData::UID uid, Member::OFF& ioff) {
	auto call_data_it = spslr_offsetof_calls.find(uid);
	if (call_data_it == spslr_offsetof_calls.end())
		return false;

	const SPSLROffsetofCallData& call_data = call_data_it->second;

	// call_data.target, call_data.member

	ioff = call_data.member;
	return true;
}

static void emit_named_asm_label_before(SPSLROffsetofCallData::UID uid, rtx_insn* before) {
	char name[128];
	snprintf(name, sizeof(name), "%s%lu:\n", SPSLR_OFFSETOF, uid);

	/* Build empty operand vectors. */
	rtvec no_out = rtvec_alloc(0);
	rtvec no_in = rtvec_alloc(0);
	rtvec no_cl = rtvec_alloc(0);
	const char* empty_constraints = "";

	/* Location: use current insn’s location if available. */
	location_t loc = INSN_LOCATION(before);

	/* Create a zero-operand, volatile asm insn. */
	rtx asmops = gen_rtx_ASM_OPERANDS (VOIDmode, ggc_strdup(name), empty_constraints, 1, no_out, no_in, no_cl, loc);

	/* Emit it right before the target insn. This does NOT affect the CFG. */
	emit_insn_before (asmops, before);
}

static void unspec_to_labeled_const(function* fn) {
	basic_block bb;
	FOR_EACH_BB_FN(bb, fn) {
		for (rtx_insn *insn = BB_HEAD(bb); insn != NEXT_INSN(BB_END(bb)); insn = NEXT_INSN(insn)) {
			if (!INSN_P(insn))
				continue;

			rtx pat = PATTERN(insn);
			if (GET_CODE(pat) != SET)
				continue;

			rtx src = SET_SRC(pat);
			if (GET_CODE(src) != UNSPEC)
				continue;

			if (XINT(src, 1) != UNSPEC_SPSLR_OFFSETOF)
				continue;

			/* Extract UID from UNSPEC operands.  */
			if (XVEC(src, 0) == NULL || XVECLEN(src, 0) < 1)
				continue;

			rtx arg = XVECEXP(src, 0, 0);
			if (!CONST_INT_P(arg))
				continue;

			SPSLROffsetofCallData::UID uid = (SPSLROffsetofCallData::UID)INTVAL(arg);
			rtx dest = SET_DEST(pat);

			Member::OFF initial_offset = uid; // TODO -> Use value that forces 32 bit (currently uses 32 bit anyways)?
			if (!lookup_initial_member_offset(uid, initial_offset)) {
				std::cerr << "Failed to query initial member offset for access uid " << uid << "!" << std::endl;
				return;
			}

			// Generate asm label
			emit_named_asm_label_before(uid, insn);

			/* 2. Replace UNSPEC with constant.  */
			rtx new_set = gen_rtx_SET(dest, GEN_INT(initial_offset));
			PATTERN(insn) = new_set;
			INSN_CODE(insn) = -1;   /* force re-recognition */

			std::cout << "Inserted labeled initial member offset " << initial_offset
				<< " for access uid " << uid << "!" << std::endl;
		}
	}
}

const pass_data unspec_to_lconst_pass_data = {
	RTL_PASS,
	"unspec_to_lconst",
	OPTGROUP_NONE,
	TV_NONE,
	PROP_rtl,
	0, 0, 0, 0
};

struct unspec_to_lconst_pass : rtl_opt_pass {
	unspec_to_lconst_pass (gcc::context *ctxt)
		: rtl_opt_pass(unspec_to_lconst_pass_data, ctxt) {}

	unsigned int execute(function* fn) override {
		unspec_to_labeled_const(fn);
		return 0;
	}
};


// Hook everything up in plugin_init

int plugin_init (struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) {
	if (!plugin_default_version_check(version, &gcc_version)) {
		fprintf(stderr, "GCC version mismatch!\n");
		std::cerr << "spslr_pinpoint -> GCC version mismatch" << std::endl;
		return 1;
	}

	register_callback(plugin_info->base_name, PLUGIN_ATTRIBUTES, on_register_attributes, NULL);
	register_callback(plugin_info->base_name, PLUGIN_FINISH_TYPE, on_type_complete, NULL);
	register_callback(plugin_info->base_name, PLUGIN_BUILD_COMPONENT_REF, on_build_component_ref, NULL);

	struct register_pass_info log_component_refs_pass_info;
	log_component_refs_pass_info.pass = new log_component_refs_pass(nullptr);
	log_component_refs_pass_info.ref_pass_instance_number = 1;
	log_component_refs_pass_info.reference_pass_name = "cfg";
	log_component_refs_pass_info.pos_op = PASS_POS_INSERT_BEFORE;
	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, nullptr, &log_component_refs_pass_info);

	struct register_pass_info print_pass_info;
	print_pass_info.pass = new print_pass(nullptr);
	print_pass_info.ref_pass_instance_number = 1;
	print_pass_info.reference_pass_name = "cfg";
	print_pass_info.pos_op = PASS_POS_INSERT_AFTER;
	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, nullptr, &print_pass_info);

	struct register_pass_info call_to_unspec_pass_info;
	call_to_unspec_pass_info.pass = new call_to_unspec_pass(nullptr);
	call_to_unspec_pass_info.reference_pass_name = "expand";
	call_to_unspec_pass_info.ref_pass_instance_number = 1;
	call_to_unspec_pass_info.pos_op = PASS_POS_INSERT_AFTER;
	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, nullptr, &call_to_unspec_pass_info);

	struct register_pass_info unspec_to_lconst_pass_info;
	unspec_to_lconst_pass_info.pass = new unspec_to_lconst_pass(nullptr);
	unspec_to_lconst_pass_info.reference_pass_name = "vregs";
	unspec_to_lconst_pass_info.ref_pass_instance_number = 1;
	unspec_to_lconst_pass_info.pos_op = PASS_POS_INSERT_BEFORE;
	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, nullptr, &unspec_to_lconst_pass_info);

	return 0;
}