From 03f6af39f446ef86cec3ec42b49f7e714906a4bd Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Thu, 25 Jun 2020 22:45:12 +0900
Subject: [PATCH] [qfcc] Reset flowvars for aliased global variables

When a global variable is accessed via only an alias in a function the
actual def's flowvar would remain in the state it was from the last
function that accessed the global normally. This would result in invalid
flowvar accesses which can be difficult to reproduce (thus no test
case).
---
 tools/qfcc/source/flow.c | 36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/tools/qfcc/source/flow.c b/tools/qfcc/source/flow.c
index e26bcef1b..86f6dc9d5 100644
--- a/tools/qfcc/source/flow.c
+++ b/tools/qfcc/source/flow.c
@@ -463,6 +463,15 @@ flow_build_statements (function_t *func)
 	}
 }
 
+static int flow_def_clear_flowvars (def_t *def, void *data)
+{
+	if (def->flowvar) {
+		delete_flowvar (def->flowvar);
+	}
+	def->flowvar = 0;
+	return 0;
+}
+
 /**	Build an array of all the variables used by a function
  *
  *	The array exists so variables can be referenced by number and thus used
@@ -517,17 +526,26 @@ flow_build_vars (function_t *func)
 	set_iter_t *var_i;
 	flowvar_t  *var;
 
-	// first, count .return and .param_[0-7] as they are always needed
+	// First, run through the statements making sure any accessed variables
+	// have their flowvars reset.  Local variables will be fine, but global
+	// variables make have had flowvars added in a previous function, and it's
+	// easier to just clear them all.
+	// This is done before .return and .param so they won't get reset just
+	// after being counted
+	for (i = 0; i < func->num_statements; i++) {
+		s = func->statements[i];
+		flow_analyze_statement (s, 0, 0, 0, operands);
+		for (j = 0; j < FLOW_OPERANDS; j++) {
+			if (operands[j] && operands[j]->op_type == op_def) {
+				def_visit_all (operands[j]->o.def, 0,
+							   flow_def_clear_flowvars, 0);
+			}
+		}
+	}
+	// count .return and .param_[0-7] as they are always needed
 	for (i = 0; i < num_flow_params; i++) {
 		def_t      *def = param_symbol (flow_params[i].name)->s.def;
-		def_t      *a;
-		for (a = def->alias_defs; a; a = a->next) {
-			if (a->flowvar) {
-				delete_flowvar (a->flowvar);
-				a->flowvar = 0;
-			}
-			//free_def (def->alias_defs);
-		}
+		def_visit_all (def, 0, flow_def_clear_flowvars, 0);
 		flow_params[i].op.o.def = def;
 		num_vars += count_operand (&flow_params[i].op);
 	}