[PATCH] D95703: [GlobalISel] Propagate extends through G_PHIs into the incoming value blocks.

[Jessica Paquette via Phabricator via llvm-commits]

paquette added inline comments.


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Comment at: llvm/include/llvm/CodeGen/TargetInstrInfo.h:1933
+  /// Given the generic extension instruction \p ExtMI, returns true if this
+  /// extension is a likely candidate for being folded into an annother
+  /// instruction.
----------------



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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:3597
+  SmallPtrSet <MachineInstr*, 4> InSrcs;
+  for (unsigned Idx = 1; Idx < MI.getNumOperands(); Idx += 2)
+    InSrcs.insert(getDefIgnoringCopies(MI.getOperand(Idx).getReg(), MRI));
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This can have at most 3 elements before returning false, so I guess you might as well cut the loop short here.


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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:3605
+
+  for (auto *DefMI : InSrcs) {
+    switch (DefMI->getOpcode()) {
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This can probably just go in the loop above, which should allow you to bail out early as well.


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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:3631
+  // deterministic iteration order.
+  SetVector<MachineInstr *> SrcMIs;
+  DenseMap<MachineInstr *, MachineInstr *> OldToNewSrcMap;
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Why not `SmallSetVector`?


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