eval: add general support for "integer functions" and add ilog2*()

Add general support in the function parser for "integer functions"
(actually implemented as special unary operators, then wrapped in
macros) and implement a family of integer logarithms.  The only
difference is the behavior on a non-power-of-two argument:

	ilog2[e]	-- throw an error
	ilog2w		-- throw a warning
	ilog2f		-- round down to power of 2
	ilog2c		-- round up to power of 2

This is useful for back-converting from masks to bit values.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/macros/ifunc.mac b/macros/ifunc.mac
new file mode 100644
index 00000000..fc0d313e
--- /dev/null
+++ b/macros/ifunc.mac
@@ -0,0 +1,46 @@
+;; --------------------------------------------------------------------------
+;;   
+;;   Copyright 2012 The NASM Authors - All Rights Reserved
+;;   See the file AUTHORS included with the NASM distribution for
+;;   the specific copyright holders.
+;;
+;;   Redistribution and use in source and binary forms, with or without
+;;   modification, are permitted provided that the following
+;;   conditions are met:
+;;
+;;   * Redistributions of source code must retain the above copyright
+;;     notice, this list of conditions and the following disclaimer.
+;;   * Redistributions in binary form must reproduce the above
+;;     copyright notice, this list of conditions and the following
+;;     disclaimer in the documentation and/or other materials provided
+;;     with the distribution.
+;;     
+;;     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+;;     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+;;     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+;;     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+;;     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+;;     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+;;     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+;;     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+;;     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+;;     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+;;     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+;;     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+;;     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+;;
+;; --------------------------------------------------------------------------
+
+;;
+;; ifunc.mac
+;;
+;; Integer function utility macros
+;;
+
+USE: ifunc
+
+%idefine ilog2(x)	(__ilog2e__(x))
+%idefine ilog2e(x)	(__ilog2e__(x))
+%idefine ilog2w(x)	(__ilog2w__(x))
+%idefine ilog2f(x)	(__ilog2f__(x))
+%idefine ilog2c(x)	(__ilog2c__(x))