================
@@ -2837,8 +2837,34 @@ void SelectionDAGBuilder::visitBr(const BranchInst &I) {
Opcode = Instruction::And;
else if (match(BOp, m_LogicalOr(m_Value(BOp0), m_Value(BOp1))))
Opcode = Instruction::Or;
-
- if (Opcode &&
+ auto &TLI = DAG.getTargetLoweringInfo();
+ const auto checkSRLIPM = [&TLI](const SDValue &Op) {
+ if (!Op.getNumOperands())
+ return false;
+ SDValue OpVal = Op.getOperand(0);
+ SDNode *N = OpVal.getNode();
+ if (N && N->getOpcode() == ISD::SRL)
+ return TLI.canLowerSRL_IPM_Switch(OpVal);
+ else if (N && OpVal.getNumOperands() &&
+ (N->getOpcode() == ISD::AND || N->getOpcode() == ISD::OR)) {
+ SDValue OpVal1 = OpVal.getOperand(0);
+ SDNode *N1 = OpVal1.getNode();
+ if (N1 && N1->getOpcode() == ISD::SRL)
+ return TLI.canLowerSRL_IPM_Switch(OpVal1);
+ }
+ return false;
+ };
+ // Incoming IR here is straight line code, FindMergedConditions splits
+ // condition code sequence across Basic Block. DAGCombiner can't combine
+ // across Basic Block. Identify SRL/IPM/CC sequence for SystemZ and avoid
+ // transformation in FindMergedConditions.
+ bool BrSrlIPM = false;
+ if (NodeMap.count(BOp0) && NodeMap[BOp0].getNode()) {
+ BrSrlIPM |= checkSRLIPM(getValue(BOp0));
+ if (NodeMap.count(BOp1) && NodeMap[BOp1].getNode())
+ BrSrlIPM &= checkSRLIPM(getValue(BOp1));
+ }
----------------
uweigand wrote:
This is already better than a target check, but there's still a whole lot of
implicitly target-specific code here. There really shouldn't be a generic
callback `canLowerSRL_IPM_Switch` - that even explicitly refers to SystemZ
instruction names! If there's target-specific behavior needed here, this should
be better abstracted.
Note that I see there's already a target hook to guide whether or not this
transformation should be performed: the `getJumpConditionMergingParams`
callback that provides input to the `shouldKeepJumpConditionsTogether`. I
think you should investigate whether we can create a SystemZ-specific
implementation of that callback that has the desired effect of inhibiting this
transformation in the cases we care about. That should then work without any
common-code change to this function.
https://github.com/llvm/llvm-project/pull/125970
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