[Issue 2756] New: Bad code generation for pure nothrow math functions

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=2756

           Summary: Bad code generation for pure nothrow math functions
           Product: D
           Version: 2.025
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: clugdbug at yahoo.com.au


Bad code generation occurs when the module is called 'std.math' in a module
statement, and the signature is exactly 'pure nothrow double XXX(double)' or
'pure nothrow float XXX(float)', and the parameter is a compile-time constant.
I suspect this is related to the special treatment of std.math.sqrt(), allowing
it to be evaluated at compile time.

----------------
MINIMAL TEST CASE:
----------------
module std.math;

pure nothrow double food(double x){ return 2.0;}

void main() {
       assert( food(1.0) == 2.0 );
}
----------------
FURTHER INFO:
----------------
module std.math;
import std.stdio;

pure nothrow float foof(float x){return 2.0;}
pure nothrow double food(double x){ return 2.0;}
pure nothrow real foor(real x) { return 2.0; }

void main() {
       writefln(foor(1.0)); // writes 2. OK.
       writefln(food(1.0)); // writes -0 !!
       writefln(foof(1.0)); // writes 0 !!
}


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