Check for poison values in fptosi and fptoui

[langston-barrett]

The LLVM language reference says:

The ‘fptoui’ instruction converts its floating-point operand into the nearest (rounding towards zero) unsigned integer value. If the value cannot fit in ty2, the result is a poison value.

and

The ‘fptosi’ instruction converts its floating-point operand into the nearest (rounding towards zero) signed integer value. If the value cannot fit in ty2, the result is a poison value.

However, it doesn't appear that we're currently checking for poison values there by adding side conditions:

crucible/crucible-llvm/src/Lang/Crucible/LLVM/Translation/Instruction.hs

Lines 550 to 568 in 1a0bd90

	L.FpToUi -> do
	outty' <- liftMemType' outty
	x' <- transTypedValue x
	let demoteToInt :: (1 <= w) => NatRepr w -> Expr (LLVM arch) s (FloatType fi) -> LLVMExpr s arch
	demoteToInt w v = BaseExpr (LLVMPointerRepr w) (BitvectorAsPointerExpr w $ App $ FloatToBV w RNE v)
	llvmTypeAsRepr outty' $ \outty'' ->
	case (asScalar x', outty'') of
	(Scalar (FloatRepr _) x'', LLVMPointerRepr w) -> return $ demoteToInt w x''
	_ -> fail (unlines [unwords ["Invalid fptoui:", show op, show x, show outty], showI])
	L.FpToSi -> do
	outty' <- liftMemType' outty
	x' <- transTypedValue x
	let demoteToInt :: (1 <= w) => NatRepr w -> Expr (LLVM arch) s (FloatType fi) -> LLVMExpr s arch
	demoteToInt w v = BaseExpr (LLVMPointerRepr w) (BitvectorAsPointerExpr w $ App $ FloatToSBV w RNE v)
	llvmTypeAsRepr outty' $ \outty'' ->
	case (asScalar x', outty'') of
	(Scalar (FloatRepr _) x'', LLVMPointerRepr w) -> return $ demoteToInt w x''
	_ -> fail (unlines [unwords ["Invalid fptosi:", show op, show x, show outty], showI])

[atomb]

This is related to #366.