target/mips: Fix minor bug in FPU
Wrong type of NaN was generated for IEEE 754-2008 by MADDF.<D|S> and MSUBF.<D|S> instructions when the arguments were (Inf, Zero, NaN) or (Zero, Inf, NaN). The if-else statement establishes if the system conforms to IEEE 754-1985 or IEEE 754-2008, and defines different behaviors depending on that. In case of IEEE 754-2008, in mentioned cases of inputs, <MADDF|MSUBF>.<D|S> returns the input value 'c' [2] (page 53) and raises floating point exception 'Invalid Operation' [1] (pages 349, 350). These scenarios were tested and the results in QEMU emulation match the results obtained on the machine that has a MIPS64R6 CPU. [1] MIPS Architecture for Programmers Volume II-a: The MIPS64 Instruction Set Reference Manual, Revision 6.06 [2] MIPS Architecture for Programmers Volume IV-j: The MIPS64 SIMD Architecture Module, Revision 1.12 Signed-off-by: Mateja Marjanovic <mateja.marjanovic@rt-rk.com> Message-Id: <1553008916-15274-2-git-send-email-mateja.marjanovic@rt-rk.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> [AJB: fixed up commit message] Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
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@ -495,15 +495,15 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
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return 1;
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}
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#elif defined(TARGET_MIPS)
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/* For MIPS, the (inf,zero,qnan) case sets InvalidOp and returns
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* the default NaN
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*/
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if (infzero) {
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float_raise(float_flag_invalid, status);
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return 3;
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}
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if (snan_bit_is_one(status)) {
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/*
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* For MIPS systems that conform to IEEE754-1985, the (inf,zero,nan)
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* case sets InvalidOp and returns the default NaN
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*/
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if (infzero) {
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float_raise(float_flag_invalid, status);
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return 3;
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}
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/* Prefer sNaN over qNaN, in the a, b, c order. */
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if (is_snan(a_cls)) {
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return 0;
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@ -519,6 +519,14 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
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return 2;
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}
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} else {
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/*
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* For MIPS systems that conform to IEEE754-2008, the (inf,zero,nan)
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* case sets InvalidOp and returns the input value 'c'
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*/
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if (infzero) {
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float_raise(float_flag_invalid, status);
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return 2;
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}
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/* Prefer sNaN over qNaN, in the c, a, b order. */
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if (is_snan(c_cls)) {
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return 2;
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