[Qemu-devel] [Bug 1841592] Re: ppc: softfloat float implementation issues

[Paul Clarke]

-- ppc64le native:
$ gcc -c -O2 ffma.c
$ gcc -O2 test-ffma.c ffma.o -lm -o test-ffma
$ ./test-ffma $(./test-ffma)
ffma(0x1p-149, 0x1p-149, 0x1p-149)
0x0

0xa000000
FE_INEXACT FE_UNDERFLOW 
0x1p-149

-- qemu-system-ppc64:
$ ./test-ffma $(./test-ffma)
ffma(0x1p-149, 0x1p-149, 0x1p-149)
0x0

0x2000000
FE_INEXACT 
0x1p-149


** Attachment added: "2nd file of float test case"
   
https://bugs.launchpad.net/qemu/+bug/1841592/+attachment/5284931/+files/ffma.c

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https://bugs.launchpad.net/bugs/1841592

Title:
  ppc: softfloat float implementation issues

Status in QEMU:
  New

Bug description:
  Per bug #1841491, Richard Henderson (rth) said:
  > The float test failure is part of a larger problem for target/powerpc
  > in which all float routines are implemented incorrectly. They are all
  > implemented as double operations with rounding to float as a second
  > step. Which not only produces incorrect exceptions, as in this case,
  > but incorrect numerical results from the double rounding.
  >
  > This should probably be split to a separate bug...

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