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, 8 insertions, 0 deletions

diff --git a/nasm.h b/nasm.h
index f7dd060..7422635 100644
--- a/nasm.h
+++ b/nasm.h
@@ -225,6 +225,7 @@ enum token_type { /* token types, other than chars */
     TOKEN_WRT,          /* WRT */
     TOKEN_FLOATIZE,     /* __floatX__ */
     TOKEN_STRFUNC,      /* __utf16*__, __utf32*__ */
+    TOKEN_IFUNC,        /* __ilog2*__ */
 };
 
 enum floatize {
@@ -248,6 +249,13 @@ enum strfunc {
     STRFUNC_UTF32BE,
 };
 
+enum ifunc {
+    IFUNC_ILOG2E,
+    IFUNC_ILOG2W,
+    IFUNC_ILOG2F,
+    IFUNC_ILOG2C,
+};
+
 size_t string_transform(char *, size_t, char **, enum strfunc);
 
 /*