From 320d6c1bd67dfea1d71e46244a74f770be2f0416 Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Mon, 22 Jun 2020 17:54:41 +0200
Subject: [PATCH] Added NEGATE_SVEC().
---
libraries/base/common/src/vhdl/common_pkg.vhd | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/libraries/base/common/src/vhdl/common_pkg.vhd b/libraries/base/common/src/vhdl/common_pkg.vhd
index 750cd5e6be..e81085087b 100644
--- a/libraries/base/common/src/vhdl/common_pkg.vhd
+++ b/libraries/base/common/src/vhdl/common_pkg.vhd
@@ -372,6 +372,9 @@ PACKAGE common_pkg IS
FUNCTION RESIZE_UVEC_32(vec : STD_LOGIC_VECTOR) RETURN STD_LOGIC_VECTOR; -- = RESIZE_UVEC() with w=32 for t_slv_32_arr slv elements
FUNCTION RESIZE_SVEC_32(vec : STD_LOGIC_VECTOR) RETURN STD_LOGIC_VECTOR; -- = RESIZE_SVEC() with w=32 for t_slv_32_arr slv elements
+
+ -- Negate vec, but avoid overflow by forcing -min to +max. Use w <= vec'LENGTH.
+ FUNCTION NEGATE_SVEC(vec : STD_LOGIC_VECTOR; w : INTEGER) RETURN STD_LOGIC_VECTOR;
FUNCTION INCR_UVEC(vec : STD_LOGIC_VECTOR; dec : INTEGER) RETURN STD_LOGIC_VECTOR;
FUNCTION INCR_UVEC(vec : STD_LOGIC_VECTOR; dec : UNSIGNED) RETURN STD_LOGIC_VECTOR;
@@ -1754,6 +1757,22 @@ PACKAGE BODY common_pkg IS
RETURN RESIZE_SVEC(vec, 32);
END;
+ -- Negate vec, but avoid overflow by forcing -min to +max. Use w <= vec'LENGTH.
+ FUNCTION NEGATE_SVEC(vec : STD_LOGIC_VECTOR; w : INTEGER) RETURN STD_LOGIC_VECTOR IS
+ CONSTANT c_max : INTEGER := 2**(w-1)-1;
+ CONSTANT c_min : INTEGER := -2**(w-1);
+ CONSTANT c_vec_w : NATURAL := vec'LENGTH;
+ VARIABLE v_vec : STD_LOGIC_VECTOR(c_vec_w-1 DOWNTO 0) := vec; -- independent of vec'RANGE
+ VARIABLE v_val : STD_LOGIC_VECTOR(w-1 DOWNTO 0);
+ BEGIN
+ v_val := v_vec(w-1 DOWNTO 0); -- operate on width w and resize to c_vec_w for return
+ IF SIGNED(v_val) = c_min THEN
+ RETURN STD_LOGIC_VECTOR(TO_SIGNED(c_max, c_vec_w)); -- most negative becomes most positive
+ ELSE
+ RETURN STD_LOGIC_VECTOR(RESIZE_NUM(-SIGNED(v_val), c_vec_w)); -- negate by multiplying by -1
+ END IF;
+ END;
+
FUNCTION INCR_UVEC(vec : STD_LOGIC_VECTOR; dec : INTEGER) RETURN STD_LOGIC_VECTOR IS
VARIABLE v_dec : INTEGER;
BEGIN
--
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