From 8f65c11d87a7dc8993d817f2db0beac9395af0a6 Mon Sep 17 00:00:00 2001 From: Tristan Gingold Date: Fri, 24 Feb 2017 05:03:39 +0100 Subject: evaluation: add comment for fp exponentiation --- src/vhdl/evaluation.adb | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src') diff --git a/src/vhdl/evaluation.adb b/src/vhdl/evaluation.adb index d996cace4..1f865a84d 100644 --- a/src/vhdl/evaluation.adb +++ b/src/vhdl/evaluation.adb @@ -1355,6 +1355,13 @@ package body Evaluation is begin Res := 1.0; Val := Get_Fp_Value (Left); + -- LRM08 9.2.8 Misellaneous operators + -- Exponentiation with an integer exponent is equivalent to + -- repeated multiplication of the left operand by itself for + -- a number of times indicated by the absolute value of the + -- exponent and from left to right; [...] + -- GHDL: use the standard power-of-2 approach. This is not + -- strictly equivalent however. Exp := abs Get_Value (Right); while Exp /= 0 loop if Exp mod 2 = 1 then @@ -1363,6 +1370,9 @@ package body Evaluation is Exp := Exp / 2; Val := Val * Val; end loop; + -- LRM08 9.2.8 Misellaneous operators + -- [...] if the exponent is negative then the result is the + -- reciprocal of that [...] if Get_Value (Right) < 0 then Res := 1.0 / Res; end if; -- cgit v1.2.3