[llvm] [AMDGPU] Introduce ABI occupancy for object linking (PR #199475)

[Gheorghe-Teodor Bercea via llvm-commits]

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@@ -224,7 +226,35 @@ AMDGPUSubtarget::getWavesPerEU(std::pair<unsigned, unsigned> FlatWorkGroupSizes,
   // Requested minimum/maximum number of waves per execution unit.
   std::pair<unsigned, unsigned> Requested =
       AMDGPU::getIntegerPairAttribute(F, "amdgpu-waves-per-eu", Default, true);
-  return getEffectiveWavesPerEU(Requested, FlatWorkGroupSizes, LDSBytes);
+  std::pair<unsigned, unsigned> WavesPerEU =
+      getEffectiveWavesPerEU(Requested, FlatWorkGroupSizes, LDSBytes);
+  if (!AMDGPUTargetMachine::EnableObjectLinking)
+    return WavesPerEU;
+
+  unsigned FunctionABIOccupancy = getFunctionABIOccupancy(F);
+  unsigned EffectiveMinWaves =
+      F.hasFnAttribute("amdgpu-waves-per-eu")
+          ? std::max(WavesPerEU.first, FunctionABIOccupancy)
+          : FunctionABIOccupancy;
+  return {EffectiveMinWaves, std::max(WavesPerEU.second, EffectiveMinWaves)};
+}
+
+unsigned AMDGPUSubtarget::getDefaultABIOccupancy(const Module &M) const {
+  unsigned Override = AMDGPU::getAMDGPUABIWavesPerEU(M);
+  if (Override)
+    Override = std::clamp(Override, getMinWavesPerEU(), getMaxWavesPerEU());
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doru1004 wrote:

Could we document this override / diagnostic it if it interferes with any user requested value?

https://github.com/llvm/llvm-project/pull/199475