[llvm] [GISel] Combine shift + trunc + shift pattern (PR #155583)

[David Green via llvm-commits]

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@@ -2094,6 +2094,70 @@ bool CombinerHelper::matchCommuteShift(MachineInstr &MI,
   return true;
 }
 
+bool CombinerHelper::matchLshrOfTruncOfLshr(MachineInstr &MI,
+                                            LshrOfTruncOfLshr &MatchInfo,
+                                            MachineInstr &ShiftMI) const {
+  unsigned ShiftOpcode = MI.getOpcode();
+  assert(ShiftOpcode == TargetOpcode::G_LSHR);
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davemgreen wrote:

asserts usually get given messages in llvm.

https://github.com/llvm/llvm-project/pull/155583