[LLVMbugs] [Bug 15109] New: Add a new warning flag indicating floats implicitly being promoted to double (similar to gcc 4.8 -Wdouble-promotion)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15109

             Bug #: 15109
           Summary: Add a new warning flag indicating floats implicitly
                    being promoted to double (similar to gcc 4.8
                    -Wdouble-promotion)
           Product: clang
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: mm at celemony.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


GCC 4.8 has a -Wdouble-promotion warning flag. Description (via
http://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html):

Give a warning when a value of type float is implicitly promoted to double.
CPUs with a 32-bit “single-precision” floating-point unit implement float in
hardware, but emulate double in software. On such a machine, doing computations
using double values is much more expensive because of the overhead required for
software emulation.
It is easy to accidentally do computations with double because floating-point
literals are implicitly of type double. For example, in:

          float area(float radius)
          {
             return 3.14159 * radius * radius;
          }

the compiler performs the entire computation with double because the
floating-point literal is a double.

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