================
@@ -2840,6 +2841,60 @@ 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:
+ //
+ // Slot1 and Slot2 are all zero bits.
+ // | Slot1 | Low | Slot2 | High |
+ // LowHigh = or (shl (zext Low), ZextLowShlAmt), (zext High)
+ // | Slot2 | High | Slot1 | Low |
+ // HighLow = or (shl (zext High), ZextHighShlAmt), (zext Low)
+ //
+ // the latter 'or' can be safely convert to
+ // -> HighLow = fshl LowHigh, LowHigh, ZextHighShlAmt
+ // if ZextLowShlAmt + ZextHighShlAmt == Width.
+ if (!isa<ZExtInst>(Or1))
+ std::swap(Or0, Or1);
+
+ Value *High, *ZextHigh, *Low;
+ const APInt *ZextHighShlAmt;
+ if (!match(Or0,
+ m_OneUse(m_Shl(m_Value(ZextHigh), m_APInt(ZextHighShlAmt)))))
+ return nullptr;
+
+ if (!match(Or1, m_ZExt(m_Value(Low))) ||
+ !match(ZextHigh, m_ZExt(m_Value(High))))
+ return nullptr;
+
+ unsigned HighSize = High->getType()->getScalarSizeInBits();
+ unsigned LowSize = Low->getType()->getScalarSizeInBits();
+ // Make sure High does not overlap with Low and most significant bits of
+ // High aren't shifted out.
+ if (ZextHighShlAmt->ult(LowSize) || ZextHighShlAmt->ugt(Width - HighSize))
+ return nullptr;
+
+ for (User *U : ZextHigh->users()) {
+ Value *X, *Y;
+ if (!match(U, m_Or(m_Value(X), m_Value(Y))))
+ continue;
+
+ if (!isa<ZExtInst>(Y))
+ std::swap(X, Y);
+
+ const APInt *ZextLowShlAmt;
+ if (!match(X, m_Shl(m_Specific(Or1), m_APInt(ZextLowShlAmt))) ||
+ !match(Y, m_Specific(ZextHigh)) || !DT.dominates(U, &Or))
+ continue;
+
+ // Make sure Low does not overlap with High and most significant bits of
+ // Low aren't shifted out and we can rotate shift LowHigh to HighLow.
+ if (ZextLowShlAmt->ult(HighSize) || ZextLowShlAmt->ugt(Width - LowSize)
||
+ *ZextLowShlAmt + *ZextHighShlAmt != Width)
----------------
goldsteinn wrote:
Think you are missing negative test for this (also for non-dominating).
https://github.com/llvm/llvm-project/pull/68502
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