fmul bug

[Biterider]

Hi
If you code fmul without arguments, UASM accepts the mnemonic but translates it to fmulp

Debugger output

Code Select Expand

  fmul
DE C9                fmulp       st(1),st


The workaround is to add some arguments like

Code Select Expand

fmul st(0), st(1)


Biterider

[jj2007]

Code Select Expand

  fld1
  fldpi
  int 3
  fmul


MASM 6.15, 15.0, UAsm:

Code Select Expand

004010B1  |.  D9E8          fld1
004010B3  |.  D9EB          fldpi
004010B5  |.  CC            int3
004010B6  |.  DEC9          fmulp st(1), st                          ; float 3.1415926535897932380 (const PI)

[HSE]

If you code fmul without arguments, UASM accepts the mnemonic but translates it to fmulp

There is no fmul without arguments, is just an alias of fmulp, Same thing happen with fadd, fsub and fdiv 

[jj2007]

Random statistics from a major source:
110*fmul, of which 3*fmul ST, ...
67*fadd, of which 2*fadd ST, ...
67*fsub, of which 0*fsub ST...

The non-popping instructions are just not that popular

[HSE]

The non-popping instructions are just not that popular

They are very popular in the form "fadd variable", etc.

[raymond]

I would NOT consider it as a BUG unless you are using some weird assembler.

The MASM assembler has never interpreted any of the arithmetic float instructions without operands otherwise but to mean popping the top register after performing the operation on the top two registers ST0 and ST1. This applies to fadd, fsub, fmul and fdiv.

And I would expect that most other assemblers would be following the same rule.

[quarantined]

I would NOT consider it as a BUG unless you are using some weird assembler.

Like uasm? lol
I never use anything other than good old (literally) masm from the masm32 SDK myself. Don't understand the need for these other variants (uasm, jwasm, etc...) if masm already does what is expected from it.

[jj2007]

I would expect that most other assemblers would be following the same rule.

UAsm and AsmC behave exactly the same, and always have done so. As Hector wrote above, fmul is an alias for fmulp.