arm: Fix floating point arguments in arm

[honggyukim]

The designated initializer in C makes implicit memset internally in arm
architecture. Due to the memset, VFP registers are clobbered
unexpectedly, so this patch fixes the problem by replacing the
designated initializer to explicit 'mcount_memset4'.

In addition, the offset of VFP registers were incorrect because the
following commit pushs d1 register on top of the original d0.

ffb69ce arm: Handle struct return type by keeping more regs on stack

So the offset is adjusted from -2 to -4 to cope with the change

Source:

  #include <stdio.h>

  float float_add(float a, float b)
  {
          fprintf(stderr, "a = %f, b = %f\n", a, b);
          return a + b;
  }

  int main(int argc, char *argv[])
  {
          double c;

          c = float_add(-0.1, 0.2);
          fprintf(stderr, "c = %f\n", c);
          return c > 0;
  }

Before:

  $ uftrace -a -F main a.out
  a = 0.000000, b = 0.000000
  c = 0.000000
  # DURATION     TID     FUNCTION
              [ 25362] | main(1, 0x7ea25344) {
              [ 25362] |   float_add(0.000000, 0.000000) {
   503.228 us [ 25362] |     fprintf(&_IO_2_1_stderr_, "a = %f, b = %f\n") = 27;
   511.197 us [ 25362] |   } = 0.000000; /* float_add */
     9.687 us [ 25362] |   fprintf(&_IO_2_1_stderr_, "c = %f\n") = 13;
   531.977 us [ 25362] | } = 0; /* main */

After:

  $ uftrace -a -F main a.out
  a = -0.100000, b = 0.200000
  c = 0.100000
  # DURATION     TID     FUNCTION
              [ 25146] | main(1, 0x7edbb344) {
              [ 25146] |   float_add(-0.100000, 0.200000) {
   501.769 us [ 25146] |     fprintf(&_IO_2_1_stderr_, "a = %f, b = %f\n") = 28;
   509.321 us [ 25146] |   } = 0.100000; /* float_add */
    12.500 us [ 25146] |   fprintf(&_IO_2_1_stderr_, "c = %f\n") = 13;
   533.539 us [ 25146] | } = 1; /* main */

Fixed: #1088

Signed-off-by: Honggyu Kim [email protected]

[namhyung]

Why not using mcount_memcpy4() here?

[honggyukim]

I cannot test this now, but changed it to mcount_memcpy4 as you suggested.

[namhyung]

You don't need to reset flag anymore.. :)

[honggyukim]

I left it to keep the original code, but removed and updated it anyway.

[namhyung]

LGTM