On Dec 20, 2007, Ian Lance Taylor <[EMAIL PROTECTED]> wrote: > It is technically feasible but problematic for other reasons. > i = i * m + ((i / j) + k) / n; > On a two register machine like the x86 i will change several times > during that calculation.
No. The register used to hold its initial value will. Keep in mind the separation between user variables and implementation locations. The user variable 'i' is only supposed to change when assignment operation is performed, (even if only in a theoretical level), when the final value of the RHS is available and stored in the location then assigned to hold the value of variable 'i'. Now, it is possible that the previous value of 'i' becomes unavailable while the expression is evaluated. Then, in order to represent this correctly, we just have to note that 'i' is no longer available as soon as all locations holding its original value are clobbered, and that it's available again when its new location holds the assigned value. -- Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/ FSF Latin America Board Member http://www.fsfla.org/ Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org} Free Software Evangelist [EMAIL PROTECTED], gnu.org}
