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UserspaceEmulator: Make error checks in FYL2XP1 and FYL2X a bit closer

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...to the manual

This removes the non complete NaN checks and fixes a bounds check in
FYL2X.
This commit is contained in:
Hendiadyoin1 2022-02-03 12:46:21 +01:00 committed by Andreas Kling
parent 60cb5b8dfa
commit 3f581c77d9
Notes: sideshowbarker 2024-07-17 17:24:08 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/3f581c77d9
Pull-request: https://github.com/SerenityOS/serenity/pull/12269
Reviewed-by: https://github.com/awesomekling ✅
1 changed files with 20 additions and 18 deletions
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38
Userland/DevTools/UserspaceEmulator/SoftFPU.cpp
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@ -1054,32 +1054,34 @@ void SoftFPU::F2XM1(const X86::Instruction&)
}
void SoftFPU::FYL2X(const X86::Instruction&)
{
// FIXME: raise precision and under/overflow
// FIXME: detect denormal operands
// FIXME: QNaN
auto f0 = fpu_get(0);
auto f1 = fpu_get(1);
if (f0 < 0. || isnan(f0) || isnan(f1)
|| (isinf(f0) && f1 == 0.) || (f0 == 1. && isinf(f1)))
// FIXME: Set C1 on when result was rounded up, cleared otherwise
// FIXME: Raise #IA #D #U #O #P
auto x = fpu_get(0);
auto y = fpu_get(1);
if (x < 0. && !isinf(x)) {
fpu_set_exception(FPU_Exception::InvalidOperation);
if (f0 == 0.)
// FIXME: Spec does not say what to do here....
// So lets just ask libm....
fpu_set(1, y * log2l(x));
} else if (x == 0.) {
if (y == 0)
fpu_set_exception(FPU_Exception::InvalidOperation);
fpu_set_exception(FPU_Exception::ZeroDivide);
fpu_set(1, f1 * log2l(f0));
fpu_set(1, INFINITY * (signbit(y) ? 1 : -1));
} else {
fpu_set(1, y * log2l(x));
}
fpu_pop();
}
void SoftFPU::FYL2XP1(const X86::Instruction&)
{
// FIXME: raise #O #U #P #D
// FIXME: QNaN
auto f0 = fpu_get(0);
auto f1 = fpu_get(1);
if (isnan(f0) || isnan(f1)
|| (isinf(f1) && f0 == 0))
// FIXME: Raise #IA #O #U #P #D
auto x = fpu_get(0);
auto y = fpu_get(1);
if (x == 0 && isinf(y))
fpu_set_exception(FPU_Exception::InvalidOperation);
fpu_set(1, (f1 * log2l(f0 + 1.0l)));
fpu_set(1, (y * log2l(x + 1.0l)));
fpu_pop();
}