[Webkit-unassigned] [Bug 179446] [JSC][MIPS] Use fcsr to check the validity of the result of trunc.w.d

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https://bugs.webkit.org/show_bug.cgi?id=179446

--- Comment #2 from Guillaume Emont <guijemont at igalia.com> ---
Created attachment 326375

  --> https://bugs.webkit.org/attachment.cgi?id=326375&action=review

Test program to check the behavior of trunc.w.d

To help me figure out what trunc.w.d does, other than using gdb on JIT'ed code, I created this little program.
On one MIPS device it outputs expected values:

trunc.w.d of 0(0): 0    invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of 42(0x4045000000000000): 0x2a       invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of -1234(0xc093480000000000): 0xfffffb2e      invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of inf(0x7ff0000000000000): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of -inf(0xfff0000000000000): 0x7fffffff       invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of nan(0x7ff7ffffffffffff): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of nan(0x7fffffffffffffff): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of 1.79769e+308(0x7fefffffffffffff): 0x7fffffff       invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of -1.79769e+308(0xffefffffffffffff): 0x7fffffff      invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of 42(0x4045000000000000): 0x2a       invalid operation cause bit: 0  invalid operation flag: 1

Though on the ci20, we get 0x80000000 for -inf and big negative values:

trunc.w.d of 0(0): 0    invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of 42(0x4045000000000000): 0x2a       invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of -1234(0xc093480000000000): 0xfffffb2e      invalid operation cause bit: 0  invalid operation flag: 0
trunc.w.d of inf(0x7ff0000000000000): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of -inf(0xfff0000000000000): 0x80000000       invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of nan(0x7ff7ffffffffffff): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of nan(0x7fffffffffffffff): 0x7fffffff        invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of 1.79769e+308(0x7fefffffffffffff): 0x7fffffff       invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of -1.79769e+308(0xffefffffffffffff): 0x80000000      invalid operation cause bit: 1  invalid operation flag: 1
trunc.w.d of 42(0x4045000000000000): 0x2a       invalid operation cause bit: 0  invalid operation flag: 1

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