From 8ec66f118a8157075694d257a18524bd619ee1ce Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Mon, 11 Sep 2023 22:56:37 +0900
Subject: [PATCH] [qfcc] Set a flowvar's minimum size based on usage

But really only for memset and memmove because they need to use an int
alias of the variable and it may be only that alias that sets a much
larger variable.
---
 tools/qfcc/include/flow.h |  1 +
 tools/qfcc/source/flow.c  | 23 ++++++++++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/qfcc/include/flow.h b/tools/qfcc/include/flow.h
index eb2d4ba20..c66d22413 100644
--- a/tools/qfcc/include/flow.h
+++ b/tools/qfcc/include/flow.h
@@ -49,6 +49,7 @@ typedef struct flowvar_s {
 	struct operand_s *op;		///< an operand using this var
 	int         number;			///< number of variable in func's ref list
 	int         flowaddr;		///< psuedo address for local and temp vars
+	int         minsize;		///< minimum size (via memset/move)
 } flowvar_t;
 
 typedef struct udchain_s {
diff --git a/tools/qfcc/source/flow.c b/tools/qfcc/source/flow.c
index b25425623..25ff5ef69 100644
--- a/tools/qfcc/source/flow.c
+++ b/tools/qfcc/source/flow.c
@@ -572,7 +572,11 @@ clear_operand_chain (operand_t *op)
 static void
 add_var_addrs (set_t *set, flowvar_t *var)
 {
-	for (int i = 0; i < var->op->size; i++) {
+	int size = var->op->size;
+	if (size < var->minsize) {
+		size = var->minsize;
+	}
+	for (int i = 0; i < size; i++) {
 		set_add (set, var->flowaddr + i);
 	}
 }
@@ -835,6 +839,17 @@ flow_add_op_var (set_t *set, operand_t *op, int ol)
 	}
 }
 
+static void
+flow_set_minsize (operand_t *op, int size)
+{
+	flowvar_t  *var;
+	if (!(var = flow_get_var (op)))
+		return;
+	if (var->minsize < size) {
+		var->minsize = size;
+	}
+}
+
 static void
 flow_add_op_var_size (set_t *set, operand_t *op, int size, int ol)
 {
@@ -1605,6 +1620,12 @@ flow_analyze_statement (statement_t *s, set_t *use, set_t *def, set_t *kill,
 					print_type (s->opb->type);
 					internal_error (s->expr, "unexpected type for memset/move");
 				}
+				if (s->type == st_move) {
+					flow_set_minsize (s->opa, size);
+				}
+				if (s->type == st_move || s->type == st_memset) {
+					flow_set_minsize (s->opc, size);
+				}
 			} else {
 				size = -1;
 			}