[llvm] [X86][CodeGen] Support lowering for CCMP/CTEST (PR #91747)
via llvm-commits
llvm-commits at lists.llvm.org
Mon May 20 08:45:55 PDT 2024
================
@@ -54605,7 +54610,132 @@ static bool onlyZeroFlagUsed(SDValue Flags) {
return true;
}
+static SDValue combineX86SubCmpToCcmpCtest(SDNode *N, SDValue Flag,
+ SelectionDAG &DAG,
+ TargetLowering::DAGCombinerInfo &DCI,
+ const X86Subtarget &ST) {
+ // cmp(and/or(setcc(cc0, flag0), setcc(cc1, sub (X, Y))), 0)
+ // brcond ne
+ //
+ // ->
+ //
+ // ccmp(X, Y, cflags/~cflags, cc0/~cc0, flag0)
+ // brcond cc1
+ //
+ //
+ // sub(and/or(setcc(cc0, flag0), setcc(cc1, sub (X, Y))), 1)
+ // brcond ne
+ //
+ // ->
+ //
+ // ccmp(X, Y, cflags/~cflags, cc0/~cc0, flag0)
+ // brcond ~cc1
+
+ // cmp(and/or(setcc(cc0, flag0), setcc(cc1, cmp (X, 0))), 0)
+ // brcond ne
+ //
+ // ->
+ //
+ // ctest(X, X, cflags/~cflags, cc0/~cc0, flag0)
+ // brcond cc1
+ //
+ //
+ // sub(and/or(setcc(cc0, flag0), setcc(cc1, cmp (X, 0))), 1)
+ // brcond ne
+ //
+ // ->
+ //
+ // ctest(X, X, cflags/~cflags, cc0/~cc0, flag0)
+ // brcond ~cc1
+
+ // if only flag has users, where cflags is determined by cc1.
+
+ SDValue LHS = N->getOperand(0);
+
+ if (!ST.hasCCMP() ||
+ (LHS.getOpcode() != ISD::AND && LHS.getOpcode() != ISD::OR) ||
+ !Flag.hasOneUse())
+ return SDValue();
+
+ SDValue SetCC0 = LHS.getOperand(0);
+ SDValue SetCC1 = LHS.getOperand(1);
+ if (SetCC0.getOpcode() != X86ISD::SETCC ||
+ SetCC1.getOpcode() != X86ISD::SETCC)
+ return SDValue();
+
+ auto GetCombineToOpc = [&](SDValue V) {
+ SDValue Op = V.getOperand(1);
+ unsigned Opc = Op.getOpcode();
+ return (Opc == X86ISD::SUB) ? X86ISD::CCMP
+ : (Opc == X86ISD::CMP && isNullConstant(Op.getOperand(1)))
+ ? X86ISD::CTEST
+ : 0U;
+ };
+
+ unsigned NewOpc = 0;
+
+ // and/or is commutable. Try to commute the operands and then test again.
+ if (!(NewOpc = GetCombineToOpc(SetCC1))) {
+ std::swap(SetCC0, SetCC1);
+ if (!(NewOpc = GetCombineToOpc(SetCC1)))
+ return SDValue();
+ }
+
+ SDValue Sub = SetCC1.getOperand(1);
+ SDNode *BrCond = *Flag->uses().begin();
+ if (BrCond->getOpcode() != X86ISD::BRCOND)
+ return SDValue();
+ unsigned CondNo = 2;
+ if (static_cast<X86::CondCode>(BrCond->getConstantOperandVal(CondNo)) !=
+ X86::COND_NE)
+ return SDValue();
+
+ X86::CondCode CC0 =
+ static_cast<X86::CondCode>(SetCC0.getConstantOperandVal(0));
+ // CCMP/CTEST is not conditional when the source condition is COND_P/COND_NP.
+ if (CC0 == X86::COND_P || CC0 == X86::COND_NP)
+ return SDValue();
----------------
goldsteinn wrote:
What about SetCC1? Also think this should be above where you do the `X86ISD::SETCC` opcode checks.
https://github.com/llvm/llvm-project/pull/91747
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