[SDAG] Introduce a new BITREVERSE node along with a corresponding LLVM intrinsic
Several backends have instructions to reverse the order of bits in an integer. Conceptually matching such patterns is similar to @llvm.bswap, and it was mentioned in http://reviews.llvm.org/D14234 that it would be best if these patterns were matched in InstCombine instead of reimplemented in every different target.
This patch introduces an intrinsic @llvm.bitreverse.i* that operates similarly to @llvm.bswap. For plumbing purposes there is also a new ISD node ISD::BITREVERSE, with simple expansion and promotion support.
The intention is that InstCombine's BSWAP detection logic will be extended to support BITREVERSE too, and @llvm.bitreverse intrinsics emitted (if the backend supports lowering it efficiently).
llvm-svn: 252878
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 8fae6e2..186697d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -145,6 +145,7 @@
SDValue PromoteLegalFP_TO_INT(SDValue LegalOp, EVT DestVT, bool isSigned,
SDLoc dl);
+ SDValue ExpandBITREVERSE(SDValue Op, SDLoc dl);
SDValue ExpandBSWAP(SDValue Op, SDLoc dl);
SDValue ExpandBitCount(unsigned Opc, SDValue Op, SDLoc dl);
@@ -2775,6 +2776,29 @@
return DAG.getNode(ISD::TRUNCATE, dl, DestVT, Operation);
}
+/// Open code the operations for BITREVERSE.
+SDValue SelectionDAGLegalize::ExpandBITREVERSE(SDValue Op, SDLoc dl) {
+ EVT VT = Op.getValueType();
+ EVT SHVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
+ unsigned Sz = VT.getSizeInBits();
+
+ SDValue Tmp, Tmp2;
+ Tmp = DAG.getConstant(0, dl, VT);
+ for (unsigned I = 0, J = Sz-1; I < Sz; ++I, --J) {
+ if (I < J)
+ Tmp2 =
+ DAG.getNode(ISD::SHL, dl, VT, Op, DAG.getConstant(J - I, dl, SHVT));
+ else
+ Tmp2 =
+ DAG.getNode(ISD::SRL, dl, VT, Op, DAG.getConstant(I - J, dl, SHVT));
+ Tmp2 =
+ DAG.getNode(ISD::AND, dl, VT, Tmp2, DAG.getConstant(1U << J, dl, VT));
+ Tmp = DAG.getNode(ISD::OR, dl, VT, Tmp, Tmp2);
+ }
+
+ return Tmp;
+}
+
/// Open code the operations for BSWAP of the specified operation.
SDValue SelectionDAGLegalize::ExpandBSWAP(SDValue Op, SDLoc dl) {
EVT VT = Op.getValueType();
@@ -2941,6 +2965,9 @@
Tmp1 = ExpandBitCount(Node->getOpcode(), Node->getOperand(0), dl);
Results.push_back(Tmp1);
break;
+ case ISD::BITREVERSE:
+ Results.push_back(ExpandBITREVERSE(Node->getOperand(0), dl));
+ break;
case ISD::BSWAP:
Results.push_back(ExpandBSWAP(Node->getOperand(0), dl));
break;
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 108c07d..3c7586d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -53,6 +53,7 @@
case ISD::AssertSext: Res = PromoteIntRes_AssertSext(N); break;
case ISD::AssertZext: Res = PromoteIntRes_AssertZext(N); break;
case ISD::BITCAST: Res = PromoteIntRes_BITCAST(N); break;
+ case ISD::BITREVERSE: Res = PromoteIntRes_BITREVERSE(N); break;
case ISD::BSWAP: Res = PromoteIntRes_BSWAP(N); break;
case ISD::BUILD_PAIR: Res = PromoteIntRes_BUILD_PAIR(N); break;
case ISD::Constant: Res = PromoteIntRes_Constant(N); break;
@@ -320,6 +321,19 @@
TLI.getShiftAmountTy(NVT, DAG.getDataLayout())));
}
+SDValue DAGTypeLegalizer::PromoteIntRes_BITREVERSE(SDNode *N) {
+ SDValue Op = GetPromotedInteger(N->getOperand(0));
+ EVT OVT = N->getValueType(0);
+ EVT NVT = Op.getValueType();
+ SDLoc dl(N);
+
+ unsigned DiffBits = NVT.getScalarSizeInBits() - OVT.getScalarSizeInBits();
+ return DAG.getNode(
+ ISD::SRL, dl, NVT, DAG.getNode(ISD::BITREVERSE, dl, NVT, Op),
+ DAG.getConstant(DiffBits, dl,
+ TLI.getShiftAmountTy(NVT, DAG.getDataLayout())));
+}
+
SDValue DAGTypeLegalizer::PromoteIntRes_BUILD_PAIR(SDNode *N) {
// The pair element type may be legal, or may not promote to the same type as
// the result, for example i14 = BUILD_PAIR (i7, i7). Handle all cases.
@@ -1263,6 +1277,7 @@
case ISD::ANY_EXTEND: ExpandIntRes_ANY_EXTEND(N, Lo, Hi); break;
case ISD::AssertSext: ExpandIntRes_AssertSext(N, Lo, Hi); break;
case ISD::AssertZext: ExpandIntRes_AssertZext(N, Lo, Hi); break;
+ case ISD::BITREVERSE: ExpandIntRes_BITREVERSE(N, Lo, Hi); break;
case ISD::BSWAP: ExpandIntRes_BSWAP(N, Lo, Hi); break;
case ISD::Constant: ExpandIntRes_Constant(N, Lo, Hi); break;
case ISD::CTLZ_ZERO_UNDEF:
@@ -1833,6 +1848,14 @@
}
}
+void DAGTypeLegalizer::ExpandIntRes_BITREVERSE(SDNode *N,
+ SDValue &Lo, SDValue &Hi) {
+ SDLoc dl(N);
+ GetExpandedInteger(N->getOperand(0), Hi, Lo); // Note swapped operands.
+ Lo = DAG.getNode(ISD::BITREVERSE, dl, Lo.getValueType(), Lo);
+ Hi = DAG.getNode(ISD::BITREVERSE, dl, Hi.getValueType(), Hi);
+}
+
void DAGTypeLegalizer::ExpandIntRes_BSWAP(SDNode *N,
SDValue &Lo, SDValue &Hi) {
SDLoc dl(N);
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
index 5d8e46b..7f4501e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
@@ -234,6 +234,7 @@
SDValue PromoteIntRes_CONCAT_VECTORS(SDNode *N);
SDValue PromoteIntRes_BITCAST(SDNode *N);
SDValue PromoteIntRes_BSWAP(SDNode *N);
+ SDValue PromoteIntRes_BITREVERSE(SDNode *N);
SDValue PromoteIntRes_BUILD_PAIR(SDNode *N);
SDValue PromoteIntRes_Constant(SDNode *N);
SDValue PromoteIntRes_CONVERT_RNDSAT(SDNode *N);
@@ -330,6 +331,7 @@
void ExpandIntRes_ADDSUB (SDNode *N, SDValue &Lo, SDValue &Hi);
void ExpandIntRes_ADDSUBC (SDNode *N, SDValue &Lo, SDValue &Hi);
void ExpandIntRes_ADDSUBE (SDNode *N, SDValue &Lo, SDValue &Hi);
+ void ExpandIntRes_BITREVERSE (SDNode *N, SDValue &Lo, SDValue &Hi);
void ExpandIntRes_BSWAP (SDNode *N, SDValue &Lo, SDValue &Hi);
void ExpandIntRes_MUL (SDNode *N, SDValue &Lo, SDValue &Hi);
void ExpandIntRes_SDIV (SDNode *N, SDValue &Lo, SDValue &Hi);
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index dffcaaa..96b8cc0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -67,6 +67,7 @@
case ISD::UNDEF: R = ScalarizeVecRes_UNDEF(N); break;
case ISD::VECTOR_SHUFFLE: R = ScalarizeVecRes_VECTOR_SHUFFLE(N); break;
case ISD::ANY_EXTEND:
+ case ISD::BITREVERSE:
case ISD::BSWAP:
case ISD::CTLZ:
case ISD::CTLZ_ZERO_UNDEF:
@@ -616,6 +617,7 @@
SplitVecRes_VECTOR_SHUFFLE(cast<ShuffleVectorSDNode>(N), Lo, Hi);
break;
+ case ISD::BITREVERSE:
case ISD::BSWAP:
case ISD::CONVERT_RNDSAT:
case ISD::CTLZ:
@@ -2027,6 +2029,7 @@
Res = WidenVecRes_Convert(N);
break;
+ case ISD::BITREVERSE:
case ISD::BSWAP:
case ISD::CTLZ:
case ISD::CTPOP:
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 5090bfb..63b5d02 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4872,6 +4872,11 @@
DAG.setRoot(Res.getValue(1));
return nullptr;
}
+ case Intrinsic::bitreverse:
+ setValue(&I, DAG.getNode(ISD::BITREVERSE, sdl,
+ getValue(I.getArgOperand(0)).getValueType(),
+ getValue(I.getArgOperand(0))));
+ return nullptr;
case Intrinsic::bswap:
setValue(&I, DAG.getNode(ISD::BSWAP, sdl,
getValue(I.getArgOperand(0)).getValueType(),
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
index 8034634..541cb36 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
@@ -311,13 +311,14 @@
case ISD::GC_TRANSITION_END: return "gc_transition.end";
// Bit manipulation
+ case ISD::BITREVERSE: return "bitreverse";
case ISD::BSWAP: return "bswap";
case ISD::CTPOP: return "ctpop";
case ISD::CTTZ: return "cttz";
case ISD::CTTZ_ZERO_UNDEF: return "cttz_zero_undef";
case ISD::CTLZ: return "ctlz";
case ISD::CTLZ_ZERO_UNDEF: return "ctlz_zero_undef";
-
+
// Trampolines
case ISD::INIT_TRAMPOLINE: return "init_trampoline";
case ISD::ADJUST_TRAMPOLINE: return "adjust_trampoline";