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[cocular]

========== Build: started ==========
OpenCL Compile Error: Compiling for device: Turks

Warning: expand kernel has register spilling. Lower performance is expected.
--------

========== Build: 1 of 1 succeeded ==========

This is AMD APP KernelAnalzer2 gives.  So do I have register spilled?

But the statistics gives:

Device    ScratchRegs    ThreadsPerWorkGroup    WavefrontSize    MaxLDSSize    LDSSize    MaxSGPRs    SGPRs    MaxVGPRs    VGPRs    ReqdWorkGroupX    ReqdWorkGroupY    ReqdWorkGroupZ
Turks    0        0            64        32768        188    N/A        N/A    248        15    0        0        0

Since I don't think my VGPRs is more than MaxVGPRs.  Why kernel has register spilling?

[himanshu_gautam]

Please attach the relevant kernel as ZIP file.

[cocular]

https://dl.dropboxusercontent.com/u/8878837/kernel.zip

[himanshu_gautam]

well in general, scratch regs can comeup before you reach MaxVGPRs, because the GPU scheduler woul try to run multiple wavefronts on a single Compute Unit, which is essential for performance. But you should certainly not get scratchregs for as low as 12-15 VGPRs (in my case). Forwarding to CodeXL team as of now.

Anyways can you confirm, if the performance of your kernel is indeed low? Compare the performance after using -cl-opt-disable flag while building kernel.

[dorono]

The messages displayed and the statistics are taken from the compiler output "as is". CodeXL and Kernel Analyzer do not interfere with this output.

[himanshu_gautam · Accepted solution]

Kernel.cl has 3 different kernels

Initialize, expand & push-back & according to the warning message “expand kernel has register spilling. Lower performance is expected”

only expand kernel has register spilling.

I think you have not changed kernel name in “Kernel Name(s)” drop down box, if he change it to expand then it will show correct values.

For me it is showing following values for expand kernel

VGPR – 37

Scratch Regs – 2