Expressions

Expressions

At source level, Jasmin program contain expressions whose concrete syntax is described below.

Expressions are made of:

• constants (true, false, 42, 0xabcd);
• packs ((4u2)[0, 3, 2, 1]);
• variables (x);
• parenthesized subexpressions ((e));
• memory loads ((u16)[p + 2 * i]);
• array accesses (x[i]);
• unary operators (- e);
• binary operators (e - f);
• conditional expressions (c ? th : el);
• function calls (f(x, y));
• primitive instructions (#copy_32(t)).

Operators

Unary operators are, by decreasing precedence:

• zero- or sign-extension ((16s)e);
• boolean / bitwise negation (! b);
• opposite (- e).

Binary operators are, by decreasing precedence:

• multiplication (x * y), division (x / y), and remainder (x % y);
• addition (x + y) and subtraction (x - y);
• shifts (x << y; x >>s y) and rotations (x <<r y; x >>r y);
• bitwise and (x & y);
• bitwise exclusive or (x ^ y);
• bitwise or (x | y);
• comparisons (x < y; x >= y);
• equality test (x == y; x != y);
• boolean conjunction (b && c);
• boolean disjunction (b || c).

Note that most operators accept as suffix a size annotation. For instance +32u is the 32-bit (unsigned) addition and +8u16 is the parallel 16-bit (unsigned) addition for vectors of 8 elements (i.e., 128 bit). Said annotation can be limited to a sign annotation, for instance >>u is the logical right shift whereas >>s is the arithmetic right shift.