[PATCH] D122615: Check if register class was changed in constrainOperandRegClass()

[Daniel Sanders via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG93977f37e67e: Check if register class was changed in constrainOperandRegClass() (authored by dsanders).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122615/new/

https://reviews.llvm.org/D122615

Files:
  llvm/lib/CodeGen/GlobalISel/Utils.cpp


Index: llvm/lib/CodeGen/GlobalISel/Utils.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -58,6 +58,11 @@
   // Assume physical registers are properly constrained.
   assert(Register::isVirtualRegister(Reg) && "PhysReg not implemented");
 
+  // Save the old register class to check whether
+  // the change notifications will be required.
+  // TODO: A better approach would be to pass
+  // the observers to constrainRegToClass().
+  auto *OldRegClass = MRI.getRegClassOrNull(Reg);
   Register ConstrainedReg = constrainRegToClass(MRI, TII, RBI, Reg, RegClass);
   // If we created a new virtual register because the class is not compatible
   // then create a copy between the new and the old register.
@@ -83,7 +88,7 @@
     if (GISelChangeObserver *Observer = MF.getObserver()) {
       Observer->changedInstr(*RegMO.getParent());
     }
-  } else {
+  } else if (OldRegClass != MRI.getRegClassOrNull(Reg)) {
     if (GISelChangeObserver *Observer = MF.getObserver()) {
       if (!RegMO.isDef()) {
         MachineInstr *RegDef = MRI.getVRegDef(Reg);


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