Closed Bug 694026 Opened 13 years ago Closed 6 years ago

MOPS access should probably be inlined even in the byte-by-byte case

Categories

(Tamarin Graveyard :: Virtual Machine, defect)

Product:
Tamarin Graveyard
Component:
Virtual Machine
Type:
defect
Priority:
Not set
Severity:
normal

Tracking

(Not tracked)

Status:
RESOLVED WONTFIX

People

(Reporter: lhansen, Unassigned)

Details

(Whiteboard: PACMAN) 

Quoting Edwin from bug #685441:

"FWIW, its also not ideal if the JIT is calling mop_anything(); the call overhead could easily be higher than the cost of the load+shift+or instructions;  See this ifdef nest in CodegenLIR.cpp:

#if NJ_EXPANDED_LOADSTORE_SUPPORTED && defined(VMCFG_UNALIGNED_INT_ACCESS) && defined(VMCFG_LITTLE_ENDIAN)
    #define VMCFG_MOPS_USE_EXPANDED_LOADSTORE_INT
#endif

#if NJ_EXPANDED_LOADSTORE_SUPPORTED && defined(VMCFG_UNALIGNED_FP_ACCESS) && defined(VMCFG_LITTLE_ENDIAN)
    #define VMCFG_MOPS_USE_EXPANDED_LOADSTORE_FP
#endif

If the VMCFG_UNALIGNED_[INT|FP]_ACCESS and VMCFG_LITTLE_ENDIAN are not set properly, then we are compiling calls to these helper functions, which will be slow."

This is the kind of thing that would make a difference on ARM, where unaligned access is frequently disabled.  We would need to prototype an in-line solution and benchmark against the current call-out solution.  (It might be adequate to do said prototyping on x86 with unaligned load/store disabled.)
Tamarin is a dead project now. Mass WONTFIX.
Status: NEW → RESOLVED
Closed: 6 years ago
Resolution: --- → WONTFIX
Tamarin isn't maintained anymore. WONTFIX remaining bugs.
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