Just a notice: I’ve updated the XE2 single-precision floating point [1] article after using the (up to now) undocumented {$EXCESSPRECISION OFF} directive, thanks to Allen Bauer for chiming in!
Executive summary: this directives enables use of single-precision SSE floating point instruction by the compiler, and brings their performance in line with expectations, making Delphi XE2 64bit compiler the new King of the Delphi Hill.
Edit: now documented here: Floating point precision control (Delphi for x64) [2]. That was fast!
Edit 2: an issue in the compiler was found related to non-explicitly typed constants by Ville Krumlinde, see QC #98753 [3], so be aware of potential incorrect code generation with the initial version of the 64 bits compiler.
Edit 3: if you happen to be one of the error insight users, it will complain that the directive doesn’t exist.
Edit 4: the compiler issue was fixed for Delphi XE2 Update1!
Let’s hope that this directive will be fully supported, and in time face the same fate as $STRINGCHECKS did (ie. become another scary story for the long winter nights).