The Tool Desk
Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
An x86 near relative CALL encodes a signed distance to its destination, not the destination’s absolute address. That makes the instruction’s bytes depend on code layout—and gives an instruction-aware PE compressor a possible pattern to exploit. But the encoding alone does not prove that a particular compressor misses savings: the available authoritative sources establish how calls and relocations work, not benchmark results.
What “relative” means in an x86 CALL
Intel documents near relative calls as E8 cw for rel16 and E8 cd for rel32. The opcode is followed by a signed displacement. The processor adds that displacement to the address immediately after the instruction to calculate the target. In 64-bit mode, the rel32 displacement is sign-extended to 64 bits. Intel’s Software Developer’s Manual, Volume 2A, gives the concise definition: “Call near, relative, displacement relative to next instruction.”
For example, if a five-byte E8 rel32 instruction begins at address 0x1000, the next instruction is at 0x1005. A displacement of 0x1B targets 0x1020:
target = address_after_CALL + sign_extended_displacement
#1 Best Overall
The four-byte operand therefore expresses a distance, not an absolute address embedded in the instruction. If code layout changes, the distance from the call to its target can change, so the displacement bytes can change too.
Not every CALL uses a relative immediate
x86 also has indirect near-call encodings, including FF /2 with a register or memory operand. Those forms obtain the target indirectly rather than storing a rel16 or rel32 immediate in the instruction. A compressor or disassembler must distinguish these encodings instead of treating every call as E8 followed by a displacement. Intel’s instruction reference lists both forms.
How CALL relates to PE and COFF relocations
Microsoft’s PE format documentation lists IMAGE_REL_I386_REL32 as a 32-bit relative displacement used for x86 relative branch and call instructions. This describes an object-file relocation used during linking; it is not evidence that every call in a finished, runtime-loaded PE has an entry in the image’s base-relocation table. Those are different relocation mechanisms at different stages. Microsoft’s PE Format reference documents the I386 relocation type.
Relative addressing can make a call target less dependent on the program’s fixed load address than an absolute address encoded directly in the instruction. That does not mean the whole program is free of absolute references or runtime relocations: other code and data references may still depend on their location.
Why relative operands might matter to PE compression
A general-purpose compressor operates on byte patterns; it need not know that a four-byte sequence is a call displacement. An instruction-aware compressor could instead parse code and try preprocessing or prediction strategies—for example, recognizing relative-call operands, normalizing them, or exploiting repeated call distances. Whether any such approach reduces an output file depends on the compressor, executable corpus, compiler and linker layout, and the cost of representing the transformed data.
That is a testable hypothesis, not an established savings claim. The instruction encoding and relocation documentation explain why operands vary with layout, but do not show that a specific PE compressor overlooks them or quantify bytes, percentages, or money saved. No outcome figure should be inferred from the presence of E8 rel32 calls alone.
What a credible compression comparison needs
To determine whether instruction-aware handling helps, compare it with a bytewise or general-purpose baseline on the same set of PE files. Keep the corpus and compressor settings fixed, and report enough detail for another person to reproduce the result.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →- Corpus: Identify the PE files, architectures, and how they were built. Compiler and linker layout can affect relative displacements.
- Baseline: Name the general-purpose compressor and settings, then compare against the instruction-aware method on identical inputs.
- Output size: Report compressed sizes for the same files and state how totals are calculated. Do not present a result from one executable as a universal PE-wide saving.
- Correctness: Decompress and verify that the output is byte-for-byte identical, or otherwise specify and validate the transformation’s correctness requirements.
- Executable details: Check that the method handles executable sections and preserves relevant PE structures, imports, and relocation behavior.
- Trade-offs: Measure decompression or runtime overhead alongside file size, and test across architectures and build layouts before generalizing.
Which reference to use for the encoding
For instruction details, consult Intel’s Software Developer’s Manual. Intel’s manuals index reports downloadable manuals at version 093 and was updated September 21, 2026; Volume 2 is the instruction-set reference. For PE/COFF relocation terminology, use Microsoft’s PE Format documentation.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
