# Recent questions tagged register-allocation

Errors violating the condition ‘any variable must be declared before its use’ are detected during semantic analysis. Why cannot it come under syntax analysis? Does declaration not fall under Syntax?
Consider the expression $(a-1) * (((b+c)/3)+d)$. Let $X$ be the minimum number of registers required by an optimal code generation (without any register spill) algorithm for a load/store architecture, in which only load and store instructions can have memory operands and arithmetic instructions can have only register or immediate operands. The value of $X$ is _____________ .
The program below uses six temporary variables $a, b, c, d, e, f$. a = 1 b = 10 c = 20 d = a + b e = c + d f = c + e b = c + e e = b + f d = 5 + e return d + f Assuming that all operations take their operands from registers, what is the minimum number of registers needed to execute this program without spilling? $2$ $3$ $4$ $6$
Consider evaluating the following expression tree on a machine with load-store architecture in which memory can be accessed only through load and store instructions. The variables $a, b, c, d,$ and $e$ are initially stored in memory. The binary operators used in this expression ... be stored in memory, what is the minimum number of registers needed to evaluate this expression? $2$ $9$ $5$ $3$
The expression $( a * b) * c \; op \dots$ where ‘op’ is one of ‘$+$’, ‘$*$’ and ‘$\uparrow$’ (exponentiation) can be evaluated on a CPU with single register without storing the value of ($a * b$) if $\text{‘op’}$ is ‘$+$’ or ‘$*$’ $\text{‘op’}$ is ‘$\uparrow$’ or ‘$*$’ $\text{‘op’}$ is ‘$\uparrow$’ or ‘$+$’ not possible to evaluate without storing