llvm dev - Jul 2010 - [LLVMdev] Splitting floating point intervals.

Hi all,

A question for the register allocation people:

I'm currently trying to split intervals over loop boundaries. I have a
situation where a floating point value is split over a loop boundary, and
the register allocator choses to spill the value outside the loop. That
leaves me with a floating point load in the loop preheader, which is
crashing LLC with

X86FloatingPoint.cpp:305:
bool<unnamed>::FPS::processBasicBlock(llvm::MachineFunction&,
llvm::MachineBasicBlock&): Assertion `isStackEmpty() && "Stack
not empty at
end of basic block?"'

What's going on here? Where do floating point values which are live over BB
boundaries live, if not on the FP stack?

Cheers,
Lang.
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On Wed, Jul 14, 2010 at 10:04 PM, Lang Hames <lhames at gmail.com>
wrote:
> Hi all,
> A question for the register allocation people:
> I'm currently trying to split intervals over loop boundaries. I have a
> situation where a floating point value is split over a loop boundary, and
> the register allocator choses to spill the value outside the loop. That
> leaves me with a floating point load in the loop preheader, which is
> crashing LLC with
> X86FloatingPoint.cpp:305:
> bool<unnamed>::FPS::processBasicBlock(llvm::MachineFunction&,
> llvm::MachineBasicBlock&): Assertion `isStackEmpty() &&
"Stack not empty at
> end of basic block?"'
> What's going on here? Where do floating point values which are live
over BB
> boundaries live, if not on the FP stack?
In memory; it's a limitation of the x87 support.

-Eli