================
@@ -2840,6 +2841,46 @@ static Instruction *matchFunnelShift(Instruction &Or,
InstCombinerImpl &IC) {
return nullptr;
FShiftArgs = {ShVal0, ShVal1, ShAmt};
+ } else if (isa<ZExtInst>(Or0) || isa<ZExtInst>(Or1)) {
+ // If there are two 'or' instructions concat variables in opposite order,
+ // the latter one can be safely convert to fshl.
+ //
+ // LowHigh = or (shl (zext Low), Width - ZextHighShlAmt), (zext High)
+ // HighLow = or (shl (zext High), ZextHighShlAmt), (zext Low)
+ // ->
+ // HighLow = fshl LowHigh, LowHigh, ZextHighShlAmt
----------------
goldsteinn wrote:
Comment doesn't seem to match the code.
Seem to matching:
`LowHigh = (zext (or Shl, Low, Width-ZExtHighShlAmt), High))`, (likewise for
high). Not `zext` on the `or` operands.
https://github.com/llvm/llvm-project/pull/68502
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