[PATCH] D105069: [GlobalISel] Add re-association combine for G_PTR_ADD to allow better addressing mode usage.

[Jessica Paquette via Phabricator via llvm-commits]

paquette added inline comments.


================
Comment at: llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h:530
 
+  bool matchReassocPtrAdd(MachineInstr &MI,
+                          std::function<void(MachineIRBuilder &)> &MatchInfo);
----------------
maybe a doxygen comment?


================
Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:4044
+  Register Src1Reg = PtrAdd.getOperand(1).getReg();
+  MachineInstr *Src1Def = MRI.getVRegDef(Src1Reg);
+  if (Src1Def->getOpcode() != TargetOpcode::G_PTR_ADD)
----------------
`getOpcodeDef`?


================
Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:4055
+  auto C2 = getConstantVRegVal(Src2Reg, MRI);
+  if (!C1 || !C2)
+    return false;
----------------
maybe minorly faster

```
auto C1 = getConstantVRegVal(Src1Def->getOperand(2).getReg(), MRI);
if (!C1)
  return false

auto C2 = getConstantVRegVal(Src2Reg, MRI);
if (!C2)
  return false;
```

You could probably pull in some of the C1/C2APIntVal stuff below into there too, although that probably matters less.




Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D105069/new/

https://reviews.llvm.org/D105069