[Bug 1892081] Re: Performance improvement when using "QEMU_FLATTEN" with softfloat type conversions

[Richard Henderson]

Confirmed, although "65% decrease" is on 0.44% of the total
execution for this test case, so the decrease isn't actually
noticeable.

Nevertheless, it's a simple enough change.

** Changed in: qemu
       Status: New => In Progress

** Changed in: qemu
     Assignee: (unassigned) => Richard Henderson (rth)

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1892081

Title:
  Performance improvement when using "QEMU_FLATTEN" with softfloat type
  conversions

Status in QEMU:
  In Progress

Bug description:
  Attached below is a matrix multiplication program for double data
  types. The program performs the casting operation "(double)rand()"
  when generating random numbers.

  This operation calls the integer to float softfloat conversion
  function "int32_to_float_64".

  Adding the "QEMU_FLATTEN" attribute to the function definition
  decreases the instructions per call of the function by about 63%.

  Attached are before and after performance screenshots from
  KCachegrind.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1892081/+subscriptions