binutils Newspaper
JULY 29, 2026
x86 Proposed

x86: Simplify register operand property checks.

Optimizes x86 assembler code by using direct type checks instead of indirect register structure access.

This patch refactors the x86 assembler’s optimize_encoding function to improve efficiency when checking operand properties. It replaces indirect accesses to register properties via i.op[n].regs->reg_type with direct accesses to i.types[n], which holds the same information but avoids an extra level of indirection, leading to slightly cleaner and potentially faster code.

In Details

Improves the x86 assembler's optimize_encoding function by changing how register operand properties are checked. Instead of dereferencing the register structure pointer (i.op[n].regs->reg_type), it directly uses the i.types[n] structure, which is populated with the same information earlier in the parsing process. This removes a layer of indirection for checks like .bitfield.word, .bitfield.qword, and .bitfield.dword.

For Context
operand
A value or variable that an instruction operates on. In assembly, operands follow the opcode.
x86 assembler
The part of binutils that processes x86 assembly language code, translating it into machine code.
optimize_encoding
A function within the assembler that attempts to use more compact instruction encodings where possible.
Filed Under: x86assembleroptimizationcode generation