[RTEMS Project] #2270: SPARC: Optimized floating-point context handling

RTEMS trac trac at rtems.org
Mon Mar 2 09:22:48 UTC 2015

#2270: SPARC: Optimized floating-point context handling
 Reporter:  sebastian.huber  |       Owner:  sebastian.huber
     Type:  enhancement      |      Status:  accepted
 Priority:  normal           |   Milestone:  4.11.1
Component:  cpukit           |     Version:  4.11
 Severity:  normal           |  Resolution:
 Keywords:  SPARC            |

Comment (by daniel):

 I guess STFSR instruction is in a way what PPC call context synchronizing.
 I don't think interrupts are different from original context switch, but
 we want to reach the ISR as fast as possible and not wait for FPU
 operations that the user has queued. That would have an impact on the
 worst-case scenario. I can't see a strict definition what happens when the
 floating point unit is turned off, just that following FP instructions
 shall result in a trap.

 page 97 - STFSR:
 The store floating-point state register instruction (STFSR) waits for any
 currently executing FPop instructions that have not completed to complete,
 and then writes the FSR into memory. STFSR may zero FSR.ftt after
 writing the FSR to memory.

Ticket URL: <http://devel.rtems.org/ticket/2270#comment:11>
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