[AMDGPU] Account workgroup size in LDS occupancy limits

Functions matching LDS use to occupancy return results for a workgroup
of 64 workitems. The numbers has to be adjusted for bigger workgroups.
For example a workgroup of size 256 already occupies 4 waves just by
itself. Given that all numbers of LDS use in the compiler are per
workgroup, occupancy shall be multiplied by 4 in this case. Each 64
workitems still limited by the same number, but 4 subrgoups 64 workitems
each can afford 4 times more LDS to get the same occupancy.

In addition change initializes LDS size in the subtarget to a real value
for SI+ targets. This is required since LDS size is a variable in these
calculations.

Differential Revision: https://reviews.llvm.org/D29423

llvm-svn: 293837

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
index f66ebd6afc2..83eda9bfbb6 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -274,11 +274,12 @@ public:
 
   /// Return the amount of LDS that can be used that will not restrict the
   /// occupancy lower than WaveCount.
-  unsigned getMaxLocalMemSizeWithWaveCount(unsigned WaveCount) const;
+  unsigned getMaxLocalMemSizeWithWaveCount(unsigned WaveCount,
+                                           const Function &) const;
 
   /// Inverse of getMaxLocalMemWithWaveCount. Return the maximum wavecount if
   /// the given LDS memory size is the only constraint.
-  unsigned getOccupancyWithLocalMemSize(uint32_t Bytes) const;
+  unsigned getOccupancyWithLocalMemSize(uint32_t Bytes, const Function &) const;
 
   bool hasFP16Denormals() const {
     return FP64FP16Denormals;