[Libre-soc-isa] [Bug 894] New: Issues with TOC immediate loading being redundant with PowerISA v3.1 pld R=1 and being CISC

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=894

            Bug ID: 894
           Summary: Issues with TOC immediate loading being redundant with
                    PowerISA v3.1 pld R=1 and being CISC
           Product: Libre-SOC's first SoC
           Version: unspecified
          Hardware: PC
               URL: https://libre-soc.org/openpower/sv/toc_data_pointer/
                OS: Linux
            Status: CONFIRMED
          Severity: normal
          Priority: ---
         Component: Specification
          Assignee: lkcl at lkcl.net
          Reporter: programmerjake at gmail.com
                CC: libre-soc-isa at lists.libre-soc.org
            Blocks: 286
   NLnet milestone: ---

Reposting my complaint here, so it doesn't get forgotten:

https://git.libre-soc.org/?p=libreriscv.git;a=blob;f=openpower/sv/toc_data_pointer.mdwn;h=74b1c9d1f2162463593ce7e0b458474039ccc361;hb=HEAD

if you have:
cmpi r3, {TOC + 8}
imho that's basically the same as x86_64's CISC-style register-memory
instruction:
cmp rax, [rip+0x1234]

imho a better approach is to instead just use the pc-relative loads added as
part of v3.1 -- pld with R=1:
pld r4, 0x1234(0), 1 # r4 = load_64(pc + 0x1234)
cmp r3, r4

no TOC needed.


Referenced Bugs:

https://bugs.libre-soc.org/show_bug.cgi?id=286
[Bug 286] DataPointer concept: long-immediate references
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