[llvm-bugs] [Bug 24599] clang++ cannot cast double to unsigned correctly.

via llvm-bugs llvm-bugs at lists.llvm.org
Fri Aug 28 19:10:23 PDT 2015


Richard Smith <richard-llvm at metafoo.co.uk> changed:

           What    |Removed                     |Added
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Richard Smith <richard-llvm at metafoo.co.uk> ---
> Target: powerpc64le-unknown-linux-gnu

Ah, this was a bug in the PPC64LE backend. Reduced testcase:

unsigned f(double d) { return d; }

int main(){
   volatile double d1 = 10.0L;
   return unsigned(d1);

Here's the assembly from 3.5 and 3.6:

    fctidz 0, 1
    stfd 0, -16(1)
    lwz 3, -12(1)

and here's the assembly from 3.7 onwards:

    xscvdpuxws 0, 1
    mfvsrwz 3, 0
    clrldi     3, 3, 32

Note that the 3.5 and 3.6 code is converting the double to a 64-bit integer,
then trying to truncate to 32 bits... but it looks like it's picking the wrong
32 bits.

Anyway, marking as fixed since it's working on trunk and in 3.7.

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