Index: llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -91,7 +91,18 @@
   /// be converted to integer, violate subtarget's specifications, or are not
   /// compatible with minimum/maximum number of waves limited by flat work group
   /// size, register usage, and/or lds usage.
-  std::pair<unsigned, unsigned> getWavesPerEU(const Function &F) const;
+  std::pair<unsigned, unsigned> getWavesPerEU(const Function &F) const {
+    // Default/requested minimum/maximum flat work group sizes.
+    std::pair<unsigned, unsigned> FlatWorkGroupSizes = getFlatWorkGroupSizes(F);
+    return getWavesPerEU(F, FlatWorkGroupSizes);
+  }
+
+  /// Overload which uses the specified values for the flat work group sizes,
+  /// rather than querying the function itself. \p FlatWorkGroupSizes Should
+  /// correspond to the function's value for getFlatWorkGroupSizes.
+  std::pair<unsigned, unsigned>
+  getWavesPerEU(const Function &F,
+                std::pair<unsigned, unsigned> FlatWorkGroupSizes) const;
 
   /// Return the amount of LDS that can be used that will not restrict the
   /// occupancy lower than WaveCount.
Index: llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
@@ -533,13 +533,10 @@
 }
 
 std::pair<unsigned, unsigned> AMDGPUSubtarget::getWavesPerEU(
-  const Function &F) const {
+    const Function &F, std::pair<unsigned, unsigned> FlatWorkGroupSizes) const {
   // Default minimum/maximum number of waves per execution unit.
   std::pair<unsigned, unsigned> Default(1, getMaxWavesPerEU());
 
-  // Default/requested minimum/maximum flat work group sizes.
-  std::pair<unsigned, unsigned> FlatWorkGroupSizes = getFlatWorkGroupSizes(F);
-
   // If minimum/maximum flat work group sizes were explicitly requested using
   // "amdgpu-flat-work-group-size" attribute, then set default minimum/maximum
   // number of waves per execution unit to values implied by requested