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  11. Apr 23, 2012
    • Preston Gurd's avatar
      This patch fixes a problem which arose when using the Post-RA scheduler · 9a091475
      Preston Gurd authored 
      on X86 Atom. Some of our tests failed because the tail merging part of
the BranchFolding pass was creating new basic blocks which did not
contain live-in information. When the anti-dependency code in the Post-RA
scheduler ran, it would sometimes rename the register containing
the function return value because the fact that the return value was
live-in to the subsequent block had been lost. To fix this, it is necessary
to run the RegisterScavenging code in the BranchFolding pass.

This patch makes sure that the register scavenging code is invoked
in the X86 subtarget only when post-RA scheduling is being done.
Post RA scheduling in the X86 subtarget is only done for Atom.

This patch adds a new function to the TargetRegisterClass to control
whether or not live-ins should be preserved during branch folding.
This is necessary in order for the anti-dependency optimizations done
during the PostRASchedulerList pass to work properly when doing
Post-RA scheduling for the X86 in general and for the Intel Atom in particular.

The patch adds and invokes the new function trackLivenessAfterRegAlloc()
instead of using the existing requiresRegisterScavenging().
It changes BranchFolding.cpp to call trackLivenessAfterRegAlloc() instead of
requiresRegisterScavenging(). It changes the all the targets that
implemented requiresRegisterScavenging() to also implement
trackLivenessAfterRegAlloc().  

It adds an assertion in the Post RA scheduler to make sure that post RA
liveness information is available when it is needed.

It changes the X86 break-anti-dependencies test to use –mcpu=atom, in order
to avoid running into the added assertion.

Finally, this patch restores the use of anti-dependency checking
(which was turned off temporarily for the 3.1 release) for
Intel Atom in the Post RA scheduler.

Patch by Andy Zhang!

Thanks to Jakob and Anton for their reviews.

llvm-svn: 155395
      9a091475
  13. Apr 17, 2012
  15. Mar 27, 2012
  17. Feb 22, 2012
  19. Feb 07, 2012
  21. Feb 02, 2012
    • Andrew Trick's avatar
      Instruction scheduling itinerary for Intel Atom. · 8523b16f
      Andrew Trick authored 
      Adds an instruction itinerary to all x86 instructions, giving each a default latency of 1, using the InstrItinClass IIC_DEFAULT.

Sets specific latencies for Atom for the instructions in files X86InstrCMovSetCC.td, X86InstrArithmetic.td, X86InstrControl.td, and X86InstrShiftRotate.td. The Atom latencies for the remainder of the x86 instructions will be set in subsequent patches.

Adds a test to verify that the scheduler is working.

Also changes the scheduling preference to "Hybrid" for i386 Atom, while leaving x86_64 as ILP.

Patch by Preston Gurd!

llvm-svn: 149558
      8523b16f
  23. Jan 31, 2012
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  59. Jul 11, 2011
    • Evan Cheng's avatar
      - Eliminate MCCodeEmitter's dependency on TargetMachine. It now uses MCInstrInfo · c5e6d2f5
      Evan Cheng authored 
        and MCSubtargetInfo.
- Added methods to update subtarget features (used when targets automatically
  detect subtarget features or switch modes).
- Teach X86Subtarget to update MCSubtargetInfo features bits since the
  MCSubtargetInfo layer can be shared with other modules.
- These fixes .code 16 / .code 32 support since mode switch is updated in
  MCSubtargetInfo so MC code emitter can do the right thing.

llvm-svn: 134884
      c5e6d2f5
  61. Jul 09, 2011
  63. Jul 08, 2011