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

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:1677
+  // to go beyond the bounds of our legal addressing modes.
+  if (!MRI.hasOneNonDBGUse(Add2))
+    return false;
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Check isLegalAddressingMode, or some similar hook?


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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:4040-4041
+    MachineInstr &PtrAdd) {
+  if (PtrAdd.getOpcode() != TargetOpcode::G_PTR_ADD)
+    return false;
+
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This should be impossible?


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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:4069-4070
+  for (auto &UseMI : MRI.use_nodbg_instructions(Src1Reg)) {
+    // This combine may end up running before ptrtoint/inttoptr combines
+    // manage to eliminate redundant conversions, so try to look through them.
+    MachineInstr *ConvUseMI = &UseMI;
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Don't we retry combines like the DAG? This seems like a bigger structural problem to solve rather than specially treating this


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

https://reviews.llvm.org/D105069