3 files changed, 18 insertions, 4 deletions
diff --git a/common/kernel/basectx.cc b/common/kernel/basectx.cc
index 82cdd835..777d06e1 100644
--- a/common/kernel/basectx.cc
+++ b/common/kernel/basectx.cc
@@ -26,6 +26,18 @@
 
 NEXTPNR_NAMESPACE_BEGIN
 
+IdString BaseCtx::idf(const char *fmt, ...) const
+{
+    std::string string;
+    va_list ap;
+
+    va_start(ap, fmt);
+    string = vstringf(fmt, ap);
+    va_end(ap);
+
+    return id(string);
+}
+
 const char *BaseCtx::nameOfBel(BelId bel) const
 {
     const Context *ctx = getCtx();
diff --git a/common/kernel/basectx.h b/common/kernel/basectx.h
index 5775e47f..c8791a2b 100644
--- a/common/kernel/basectx.h
+++ b/common/kernel/basectx.h
@@ -162,6 +162,8 @@ struct BaseCtx
 
     IdString id(const char *s) const { return IdString(this, s); }
 
+    IdString idf(const char *fmt, ...) const; // create IdString using printf formatting
+
     Context *getCtx() { return as_ctx; }
 
     const Context *getCtx() const { return as_ctx; }
diff --git a/common/kernel/nextpnr_types.cc b/common/kernel/nextpnr_types.cc
index 8563eb27..6da37763 100644
--- a/common/kernel/nextpnr_types.cc
+++ b/common/kernel/nextpnr_types.cc
@@ -152,8 +152,8 @@ void CellInfo::movePortBusTo(IdString old_name, int old_offset, bool old_bracket
                              IdString new_name, int new_offset, bool new_brackets, int width)
 {
     for (int i = 0; i < width; i++) {
-        IdString old_port = ctx->id(stringf(old_brackets ? "%s[%d]" : "%s%d", old_name.c_str(ctx), i + old_offset));
-        IdString new_port = ctx->id(stringf(new_brackets ? "%s[%d]" : "%s%d", new_name.c_str(ctx), i + new_offset));
+        IdString old_port = ctx->idf(old_brackets ? "%s[%d]" : "%s%d", old_name.c_str(ctx), i + old_offset);
+        IdString new_port = ctx->idf(new_brackets ? "%s[%d]" : "%s%d", new_name.c_str(ctx), i + new_offset);
         movePortTo(old_port, new_cell, new_port);
     }
 }
@@ -171,8 +171,8 @@ void CellInfo::copyPortBusTo(IdString old_name, int old_offset, bool old_bracket
                              IdString new_name, int new_offset, bool new_brackets, int width)
 {
     for (int i = 0; i < width; i++) {
-        IdString old_port = ctx->id(stringf(old_brackets ? "%s[%d]" : "%s%d", old_name.c_str(ctx), i + old_offset));
-        IdString new_port = ctx->id(stringf(new_brackets ? "%s[%d]" : "%s%d", new_name.c_str(ctx), i + new_offset));
+        IdString old_port = ctx->idf(old_brackets ? "%s[%d]" : "%s%d", old_name.c_str(ctx), i + old_offset);
+        IdString new_port = ctx->idf(new_brackets ? "%s[%d]" : "%s%d", new_name.c_str(ctx), i + new_offset);
         copyPortTo(old_port, new_cell, new_port);
     }
 }