[llvm] [GlobalISel] Introduce `G_POISON` (PR #127825)

[Matt Arsenault via llvm-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/127825 at github.com>


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@@ -1566,6 +1568,7 @@ bool llvm::isAllOnesOrAllOnesSplat(const MachineInstr &MI,
                                    const MachineRegisterInfo &MRI,
                                    bool AllowUndefs) {
   switch (MI.getOpcode()) {
+  case TargetOpcode::G_POISON:
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arsenm wrote:

This will need revisiting, poison could be more aggressive here 

https://github.com/llvm/llvm-project/pull/127825