How does Go compare strings under the hood?

Go's String Comparison: Behind the Scenes

Go offers straightforward string comparison without the need for specialized functions. However, it's worth exploring if the Go runtime performs any background operations when comparing string literals.

String Comparison in Go's Assembly Code

The specification states that string comparison in Go is performed using the '==' operator. An in-depth look into the compiler's generated assembly code reveals the following process:

• Initially, a check is made to see if the two string operands reside at the same memory address (in-memory string).
• If the check fails, string comparison is delegated to a 'runtime.eqstring' function in the runtime.

The code below illustrates this process:

CMPQ    CX,AX
JNE     ,22
CMPQ    SI,(SP)
MOVQ    CX,8(SP)
MOVQ    DX,16(SP)
MOVQ    AX,24(SP)
CALL    ,runtime.eqstring+0(SB)

The runtime.eqstring function performs the actual string comparison.

Implications for Developers

For developers, this internal process should not be a major concern. String comparisons can be performed using the operators defined in the specification, which ensures O(n) complexity with the string's length.

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