[llvm] [GlobalIsel][NFC] Modernize UBFX combine (PR #97513)

[Thorsten Schütt via llvm-commits]

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@@ -4521,19 +4521,21 @@ bool CombinerHelper::matchBitfieldExtractFromSExtInReg(
 }
 
 /// Form a G_UBFX from "(a srl b) & mask", where b and mask are constants.
-bool CombinerHelper::matchBitfieldExtractFromAnd(
-    MachineInstr &MI, std::function<void(MachineIRBuilder &)> &MatchInfo) {
-  assert(MI.getOpcode() == TargetOpcode::G_AND);
-  Register Dst = MI.getOperand(0).getReg();
+bool CombinerHelper::matchBitfieldExtractFromAnd(MachineInstr &MI,
+                                                 BuildFnTy &MatchInfo) {
+  GAnd *And = cast<GAnd>(&MI);
+  Register Dst = And->getReg(0);
   LLT Ty = MRI.getType(Dst);
   LLT ExtractTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
+  // Note that isLegalOrBeforeLegalizer is stricter and does not take custom
+  // into account.
   if (LI && !LI->isLegalOrCustom({TargetOpcode::G_UBFX, {Ty, ExtractTy}}))
     return false;
 
   int64_t AndImm, LSBImm;
   Register ShiftSrc;
   const unsigned Size = Ty.getScalarSizeInBits();
-  if (!mi_match(MI.getOperand(0).getReg(), MRI,
+  if (!mi_match(And->getReg(0), MRI,
                 m_GAnd(m_OneNonDBGUse(m_GLShr(m_Reg(ShiftSrc), m_ICst(LSBImm))),
                        m_ICst(AndImm))))
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tschuett wrote:

1. It is collecting registers and int64_t s.
2. `mi_match` returns a boolean. I don't want to and cannot ignore it.
3. I could add a comment: "Cannot fail due to pattern."

https://github.com/llvm/llvm-project/pull/97513