[llvm-commits] [llvm] r76680 - in /llvm/trunk/lib/CodeGen: LiveInterval.cpp SimpleRegisterCoalescing.cpp

[Bill Wendling]

Hi David,


> Add some support for iterative coalescers to calculate a joined live
> range's weight properly.  This is turned off right now in the sense that
> you'll get an assert if you get into a situation that can only be caused
> by an iterative coalescer.  All other code paths operate exactly as
> before so there is no functional change with this patch.  The asserts
> should be disabled if/when an iterative coalescer gets added to trunk.
>
> -  weight += Other.weight;
> +  // If either of these intervals was spilled, the weight is the
> +  // weight of the non-spilled interval.  This can only happen with
> +  // iterative coalescers.
> +
> +  if (weight == HUGE_VALF && !TargetRegisterInfo::isPhysicalRegister(reg)) {
> +    // Remove this assert if you have an iterative coalescer
> +    assert(0 && "Joining to spilled interval");
> +    weight = Other.weight;
> +  }
> +  else if (Other.weight != HUGE_VALF) {
> +    weight += Other.weight;

Since this is the only  option available at this time, please make
this the first "if-then" statement instead of the one above it, which
asserts all of the time.

> +  }
> +  else {
> +    // Remove this assert if you have an iterative coalescer
> +    assert(0 && "Joining from spilled interval");
> +  }
> +  // Otherwise the weight stays the same
>
This comment is confusing. Should it be moved into the "-else" part?

>   // Update regalloc hint if currently there isn't one.
>   if (TargetRegisterInfo::isVirtualRegister(reg) &&
>
> Modified: llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp?rev=76680&r1=76679&r2=76680&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp Tue Jul 21 18:36:14 2009
> @@ -1969,7 +1969,24 @@
>     LHSValNo->setHasPHIKill(true);
>   LHS.addKills(LHSValNo, VNI->kills);
>   LHS.MergeRangesInAsValue(RHS, LHSValNo);
> -  LHS.weight += RHS.weight;
> +
> +  // If either of these intervals was spilled, the weight is the
> +  // weight of the non-spilled interval.  This can only happen
> +  // with iterative coalescers.
> +  if (LHS.weight == HUGE_VALF && !TargetRegisterInfo::isPhysicalRegister(LHS.reg)) {
> +    // Remove this assert if you have an iterative coalescer
> +    assert(0 && "Joining to spilled interval");
> +    LHS.weight = RHS.weight;
> +  }
> +  else if (RHS.weight != HUGE_VALF) {
> +    LHS.weight += RHS.weight;
> +  }

Same comment here as above.

> +  else {
> +    // Remove this assert if you have an iterative coalescer
> +    assert(0 && "Joining from spilled interval");
> +  }
> +
> +  // Otherwise the LHS weight stays the same
>
And here.

-bw