[PATCH] D59836: PEI: Delay checking requiresFrameIndexReplacementScavenging

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: qcolombet, MatzeB, thegameg.
Herald added subscribers: arphaman, tpr, wdng.

Currently this is called before the frame size is set on the
function. For AMDGPU, the scavenger is used for large frames where
part of the offset needs to be materialized in a register, so
estimating the frame size is useful for knowing whether the scavenger
is useful.


https://reviews.llvm.org/D59836

Files:
  lib/CodeGen/PrologEpilogInserter.cpp


Index: lib/CodeGen/PrologEpilogInserter.cpp
===================================================================
--- lib/CodeGen/PrologEpilogInserter.cpp
+++ lib/CodeGen/PrologEpilogInserter.cpp
@@ -218,8 +218,6 @@
 
   RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : nullptr;
   FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(MF);
-  FrameIndexEliminationScavenging = (RS && !FrameIndexVirtualScavenging) ||
-    TRI->requiresFrameIndexReplacementScavenging(MF);
   ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
 
   // Calculate the MaxCallFrameSize and AdjustsStack variables for the
@@ -1074,8 +1072,16 @@
 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
 /// register references and actual offsets.
 void PEI::replaceFrameIndices(MachineFunction &MF) {
-  const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
-  if (!TFI.needsFrameIndexResolution(MF)) return;
+  const auto &ST = MF.getSubtarget();
+  const TargetFrameLowering &TFI = *ST.getFrameLowering();
+  if (!TFI.needsFrameIndexResolution(MF))
+    return;
+
+  const TargetRegisterInfo *TRI = ST.getRegisterInfo();
+
+  // Allow the target to determine this after knowing the frame size.
+  FrameIndexEliminationScavenging = (RS && !FrameIndexVirtualScavenging) ||
+    TRI->requiresFrameIndexReplacementScavenging(MF);
 
   // Store SPAdj at exit of a basic block.
   SmallVector<int, 8> SPState;


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