[Rd] How to ensure -O3 on Win64

[Matthew Dowle]

Hi,

Similar questions have come up before on the list and elsewhere but I 
haven't found a solution yet.

winbuilder's install.out shows data.table's .c files compiled with -O3 
on Win32 but -O2 on Win64. The same happens on R-Forge. I gather that 
some packages don't work with -O3 so the default is -O2.

I've tried this in data.table's Makevars (entire contents) :

====
MAKEFLAGS="CFLAGS=-O3"                        # added
CFLAGS=-O3                                    # added
PKG_CFLAGS=-O3                                # added
all: $(SHLIB)                                 # no change
	mv $(SHLIB) datatable$(SHLIB_EXT)     # no change
====

but -O2 still appears in winbuilder's install.out (after -O3, and I 
believe the last -O is the one that counts) :

gcc -m64 -I"D:/RCompile/recent/R-2.15.2/include" -DNDEBUG     
-I"d:/Rcompile/CRANpkg/extralibs215/local215/include"  -O3   -O2 -Wall  
-std=gnu99 -mtune=core2 -c dogroups.c -o dogroups.o

How can I ensure that data.table is compiled with -O3 on Win64?

Thanks, Matthew