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Fix synthesis of concatentation to always make result unsigned. 

When there is only one operand, we elide the concatenation during
expression synthesis. But if that operand is signed, we need to
insert an intermediate local signel to cast it to unsigned.

This fixes issue #1099.
This commit is contained in:
Martin Whitaker 2024-02-24 11:39:22 +00:00
parent 61943c844d
commit 09a134d973
1 changed files with 12 additions and 1 deletions
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13
expr_synth.cc
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1999-2021 Stephen Williams (steve@icarus.com)
* Copyright (c) 1999-2024 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
@ -818,6 +818,17 @@ NetNet* NetEConcat::synthesize(Design*des, NetScope*scope, NetExpr*root)
}
}
ivl_assert(*this, osig);
if (osig->get_signed()) {
// A concatenation is always unsigned, so make a new signal to
// reflect this.
NetNet*isig = osig;
auto osig_vec = new netvector_t(data_type, isig->vector_width() - 1, 0);
osig = new NetNet(scope, scope->local_symbol(), NetNet::IMPLICIT,
osig_vec);
osig->set_line(*this);
osig->local_flag(true);
connect(isig->pin(0), osig->pin(0));
}
}
if (repeat() != 1) {