GATE CS 2003 Q57 — Parsing (LL, LR)

Which of the following statements is/are true?

Consider the control flow graph shown in the figure. Which one of the following options correctly lists the set of redundant expressions (common subexpressions) in the basic blocks B$4$ and B$5$? Note: All the variables are integers.

Which of the following grammars is/are ambiguous?

Consider the canonical $L R(0)$ parsing of the grammar below using terminals $\{a, b, c\}$ and non-terminals $\{A, B, C, S\}$ with $S$ as the start symbol. $$\begin{array}{l} S \rightarrow A C B \\ A \rightarrow a A \mid \epsilon \\ C \rightarrow c C \mid \epsilon \\ B \rightarrow b B \mid b \end{array}$$ Which one of the following options gives the …

Which of the following statement(s) is/are TRUE while computing $\operatorname{First}$ and $\operatorname{Follow}$ during top down parsing by a compiler?

Consider two grammars $G_{1}$ and $G_{2}$ with the production rules given below: $G_{1} : S \rightarrow$ $if$ $E$ $then$ $S$ $|$ $if$ $E$ $then$ $S$ $else$ $S$ $|$ $a$ $E \rightarrow b$ $G_{2} :S \rightarrow$ $if$ $E$ $then$ $S$ $|$ $M$ $M \rightarrow$ $if$ $E$ $then$ $M$ $else$ $S$ $|$ $c$ …