From 3156226233133f5da9dba15c63ca560b4794b831 Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Thu, 15 Jul 2021 10:36:50 -0400
Subject: verilog: save and restore overwritten macro arguments

---
 frontends/verilog/preproc.cc | 34 ++++++++++++++++++++++++++++++----
 frontends/verilog/preproc.h  |  1 +
 2 files changed, 31 insertions(+), 4 deletions(-)

(limited to 'frontends/verilog')

diff --git a/frontends/verilog/preproc.cc b/frontends/verilog/preproc.cc
index 4b9ebe0aa..17f567587 100644
--- a/frontends/verilog/preproc.cc
+++ b/frontends/verilog/preproc.cc
@@ -36,6 +36,7 @@
 #include "verilog_frontend.h"
 #include "kernel/log.h"
 #include <assert.h>
+#include <stack>
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
@@ -334,6 +335,11 @@ define_map_t::add(const std::string &name, const std::string &txt, const arg_map
 	defines[name] = std::unique_ptr<define_body_t>(new define_body_t(txt, args));
 }
 
+void define_map_t::add(const std::string &name, const define_body_t &body)
+{
+	defines[name] = std::unique_ptr<define_body_t>(new define_body_t(body));
+}
+
 void define_map_t::merge(const define_map_t &map)
 {
 	for (const auto &pr : map.defines) {
@@ -440,7 +446,17 @@ static bool read_argument(std::string &dest)
 	}
 }
 
-static bool try_expand_macro(define_map_t &defines, std::string &tok)
+using macro_arg_stack_t = std::stack<std::pair<std::string, define_body_t>>;
+
+static void restore_macro_arg(define_map_t &defines, macro_arg_stack_t &macro_arg_stack)
+{
+	log_assert(!macro_arg_stack.empty());
+	auto &overwritten_arg = macro_arg_stack.top();
+	defines.add(overwritten_arg.first, overwritten_arg.second);
+	macro_arg_stack.pop();
+}
+
+static bool try_expand_macro(define_map_t &defines, macro_arg_stack_t &macro_arg_stack, std::string &tok)
 {
 	if (tok == "`\"") {
 		std::string literal("\"");
@@ -450,7 +466,7 @@ static bool try_expand_macro(define_map_t &defines, std::string &tok)
 			if (ntok == "`\"") {
 				insert_input(literal+"\"");
 				return true;
-			} else if (!try_expand_macro(defines, ntok)) {
+			} else if (!try_expand_macro(defines, macro_arg_stack, ntok)) {
 					literal += ntok;
 			}
 		}
@@ -495,6 +511,10 @@ static bool try_expand_macro(define_map_t &defines, std::string &tok)
 			args.push_back(arg);
 		}
 		for (const auto &pr : body->args.get_vals(name, args)) {
+			if (const define_body_t *existing = defines.find(pr.first)) {
+				macro_arg_stack.push({pr.first, *existing});
+				insert_input("`__restore_macro_arg ");
+			}
 			defines.add(pr.first, pr.second);
 		}
 	} else {
@@ -725,6 +745,7 @@ frontend_verilog_preproc(std::istream                 &f,
 	defines.merge(pre_defines);
 	defines.merge(global_defines_cache);
 
+	macro_arg_stack_t macro_arg_stack;
 	std::vector<std::string> filename_stack;
 	// We are inside pass_level levels of satisfied ifdefs, and then within
 	// fail_level levels of unsatisfied ifdefs.  The unsatisfied ones are
@@ -828,7 +849,7 @@ frontend_verilog_preproc(std::istream                 &f,
 		if (tok == "`include") {
 			skip_spaces();
 			std::string fn = next_token(true);
-			while (try_expand_macro(defines, fn)) {
+			while (try_expand_macro(defines, macro_arg_stack, fn)) {
 				fn = next_token();
 			}
 			while (1) {
@@ -935,7 +956,12 @@ frontend_verilog_preproc(std::istream                 &f,
 			continue;
 		}
 
-		if (try_expand_macro(defines, tok))
+		if (tok == "`__restore_macro_arg") {
+			restore_macro_arg(defines, macro_arg_stack);
+			continue;
+		}
+
+		if (try_expand_macro(defines, macro_arg_stack, tok))
 			continue;
 
 		output_code.push_back(tok);
diff --git a/frontends/verilog/preproc.h b/frontends/verilog/preproc.h
index e1048156c..330855a92 100644
--- a/frontends/verilog/preproc.h
+++ b/frontends/verilog/preproc.h
@@ -42,6 +42,7 @@ struct define_map_t
 
 	// Add a definition, overwriting any existing definition for name.
 	void add(const std::string &name, const std::string &txt, const arg_map_t *args = nullptr);
+	void add(const std::string &name, const define_body_t &body);
 
 	// Merge in another map of definitions (which take precedence
 	// over anything currently defined).
-- 
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