[ValueTracking] bitreverse, sin, cos are safe to speculatively execute

[arsenm]

Needs tests. Bitreverse is definitely OK, but I'm not sure about sin/cos. The math function handling is a mess and they might need to be assumed to set errno (although I don't see why this is the case since the libcall can work for targets with this problem)

[mareko]

I'd also like to mark UDiv, URem, SDiv, SRem, exp2, log2, pow, and at least 14 AMDGPU intrinsics as speculatively-executable.

All of those have no side effects on AMDGPU. Right now, we are losing some performance here.

[arsenm]

The divisions can't be speculated because divide by 0 is undefined behavior. The AMDGPU intrinsics and bitreverse are now speculatable

lib/Analysis/ValueTracking.cpp

if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
       // These synthetic intrinsics have no side-effects and just mark
       // information about their operands.
       // FIXME: There are other no-op synthetic instructions that potentially
       // should be considered at least *safe* to speculate...
       case Intrinsic::dbg_declare:
       case Intrinsic::dbg_value:
         return true;
 
+      case Intrinsic::bitreverse:
       case Intrinsic::bswap:
       case Intrinsic::ctlz:
       case Intrinsic::ctpop:
       case Intrinsic::cttz:
       case Intrinsic::objectsize:
       case Intrinsic::sadd_with_overflow:
       case Intrinsic::smul_with_overflow:
       case Intrinsic::ssub_with_overflow:
       case Intrinsic::uadd_with_overflow:
       case Intrinsic::umul_with_overflow:
       case Intrinsic::usub_with_overflow:
         return true;
       // These intrinsics are defined to have the same behavior as libm
       // functions except for setting errno.
       case Intrinsic::sqrt:
       case Intrinsic::fma:
       case Intrinsic::fmuladd:
         return true;
       // These intrinsics are defined to have the same behavior as libm
       // functions, and the corresponding libm functions never set errno.
+      case Intrinsic::sin:
+      case Intrinsic::cos:
       case Intrinsic::trunc:
       case Intrinsic::copysign:
       case Intrinsic::fabs:
       case Intrinsic::minnum:
       case Intrinsic::maxnum:
         return true;
       // These intrinsics are defined to have the same behavior as libm
       // functions, which never overflow when operating on the IEEE754 types