Nehalem supports SSE4.2

Signed Off By: Max Howell <max@methylblue.com>

I realised that -msse4.1 and -msse4.2 aren't supported by GCC 4.0, so I made
the brash decision that we require GCC 4.2. It comes with Xcode 3.1 so people
can upgrade if they have to.

Requiring a single compiler is better for us anyway -- less possible errors
and failures.

Formulae can still request gcc-4.0.1, but at least then those formulae still
only use a single compiler and not possibly two.

Library/Homebrew/brewkit.rb

@@ -64,15 +64,14 @@ else
   end
   cflags<<"-mfpmath=sse"
   
-  # use gcc 4.2 if available (Xcode 3.1 and above)
-  if system "which -s gcc-4.2" and $?.success?
   ENV['CC']="gcc-4.2"
   ENV['CXX']="g++-4.2"
-  end
 end
 
 cflags<<"-mmmx"
 case Hardware.intel_family
+when :nehalem
+  cflags<<"-msse4.2"
 when :penryn
   cflags<<"-msse4.1"
 when :core2, :core
@@ -107,8 +106,10 @@ module HomebrewEnvExtension
     when 10.6..11.0
       self['CC']='gcc-4.0'
       self['CXX']='g++-4.0'
-      remove_from_cflags '-march=core2' # we *should* add back in stuff but meh for now
+      remove_from_cflags '-march=core2'
     end
+    remove_from_cflags '-msse4.1'
+    remove_from_cflags '-msse4.2'
   end
   def osx_10_4
     self['MACOSX_DEPLOYMENT_TARGET']=nil

bin/brew

@@ -34,7 +34,9 @@ end
 if Hardware.cpu_type == :ppc or Hardware.cpu_type == :dunno
   abort "Sorry, Homebrew does not support your computer's CPU architecture."
 end
-
+unless system "which gcc-4.2 &> /dev/null" and $?.success?
+  abort "Sorry, Homebrew requires gcc 4.2, which is provided by Xcode 3.1"
+end
 
 begin
   case ARGV.shift