[PPC] Move the combine "a << (b % (sizeof(a) * 8)) -> (PPCshl a, b)" to the backend...

Summary:
Eli pointed out that it's unsafe to combine the shifts to ISD::SHL etc.,
because those are not defined for b > sizeof(a) * 8, even after some of
the combiners run.

However, PPCISD::SHL defines that behavior (as the instructions themselves).
Move the combination to the backend.

The tests in shift_mask.ll still pass.

Reviewers: echristo, hfinkel, efriedma, iteratee

Subscribers: nemanjai, llvm-commits

Differential Revision: https://reviews.llvm.org/D33076

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302937 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index e282ca157708c03155b64b61ed5eefff92042b6c..1ca32d4c35898d88d604a4e928028f8dad314856 100644 (file)
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -2063,14 +2063,6 @@ public:
     return false;
   }
 
-  // Return true if the instruction that performs a << b actually performs
-  // a << (b % (sizeof(a) * 8)).
-  virtual bool supportsModuloShift(ISD::NodeType Inst, EVT ReturnType) const {
-    assert((Inst == ISD::SHL || Inst == ISD::SRA || Inst == ISD::SRL) &&
-           "Expect a shift instruction");
-    return false;
-  }
-
   //===--------------------------------------------------------------------===//
   // Runtime Library hooks
   //

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5f6c6fd4508393d0ac44ca0c51ff73f0c16d7c1c..fb8c50a4d69dc239d451efba43c074870c2f8476 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5313,17 +5313,6 @@ SDValue DAGCombiner::visitSHL(SDNode *N) {
     }
   }
 
-  // If the target supports masking y in (shl, y),
-  // fold (shl x, (and y, ((1 << numbits(x)) - 1))) -> (shl x, y)
-  if (TLI.isOperationLegal(ISD::SHL, VT) &&
-      TLI.supportsModuloShift(ISD::SHL, VT) && N1->getOpcode() == ISD::AND) {
-    if (ConstantSDNode *Mask = isConstOrConstSplat(N1->getOperand(1))) {
-      if (Mask->getZExtValue() == OpSizeInBits - 1) {
-        return DAG.getNode(ISD::SHL, SDLoc(N), VT, N0, N1->getOperand(0));
-      }
-    }
-  }
-
   ConstantSDNode *N1C = isConstOrConstSplat(N1);
 
   // fold (shl c1, c2) -> c1<<c2
@@ -5522,17 +5511,6 @@ SDValue DAGCombiner::visitSRA(SDNode *N) {
   EVT VT = N0.getValueType();
   unsigned OpSizeInBits = VT.getScalarSizeInBits();
 
-  // If the target supports masking y in (sra, y),
-  // fold (sra x, (and y, ((1 << numbits(x)) - 1))) -> (sra x, y)
-  if (TLI.isOperationLegal(ISD::SRA, VT) &&
-      TLI.supportsModuloShift(ISD::SRA, VT) && N1->getOpcode() == ISD::AND) {
-    if (ConstantSDNode *Mask = isConstOrConstSplat(N1->getOperand(1))) {
-      if (Mask->getZExtValue() == OpSizeInBits - 1) {
-        return DAG.getNode(ISD::SRA, SDLoc(N), VT, N0, N1->getOperand(0));
-      }
-    }
-  }
-
   // Arithmetic shifting an all-sign-bit value is a no-op.
   // fold (sra 0, x) -> 0
   // fold (sra -1, x) -> -1
@@ -5687,17 +5665,6 @@ SDValue DAGCombiner::visitSRL(SDNode *N) {
   EVT VT = N0.getValueType();
   unsigned OpSizeInBits = VT.getScalarSizeInBits();
 
-  // If the target supports masking y in (srl, y),
-  // fold (srl x, (and y, ((1 << numbits(x)) - 1))) -> (srl x, y)
-  if (TLI.isOperationLegal(ISD::SRL, VT) &&
-      TLI.supportsModuloShift(ISD::SRL, VT) && N1->getOpcode() == ISD::AND) {
-    if (ConstantSDNode *Mask = isConstOrConstSplat(N1->getOperand(1))) {
-      if (Mask->getZExtValue() == OpSizeInBits - 1) {
-        return DAG.getNode(ISD::SRL, SDLoc(N), VT, N0, N1->getOperand(0));
-      }
-    }
-  }
-
   // fold vector ops
   if (VT.isVector())
     if (SDValue FoldedVOp = SimplifyVBinOp(N))

diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index 5de774ea372162008ba8cfef2b7e33a9351b1b92..17bdd595da109a848f0b5da0cb24a3e40d9ed77a 100644 (file)
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -923,6 +923,9 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
   setStackPointerRegisterToSaveRestore(isPPC64 ? PPC::X1 : PPC::R1);
 
   // We have target-specific dag combine patterns for the following nodes:
+  setTargetDAGCombine(ISD::SHL);
+  setTargetDAGCombine(ISD::SRA);
+  setTargetDAGCombine(ISD::SRL);
   setTargetDAGCombine(ISD::SINT_TO_FP);
   setTargetDAGCombine(ISD::BUILD_VECTOR);
   if (Subtarget.hasFPCVT())
@@ -11312,6 +11315,12 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
   SDLoc dl(N);
   switch (N->getOpcode()) {
   default: break;
+  case ISD::SHL:
+    return combineSHL(N, DCI);
+  case ISD::SRA:
+    return combineSRA(N, DCI);
+  case ISD::SRL:
+    return combineSRL(N, DCI);
   case PPCISD::SHL:
     if (isNullConstant(N->getOperand(0))) // 0 << V -> 0.
         return N->getOperand(0);
@@ -12944,3 +12953,58 @@ bool PPCTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT) const {
     return Imm.isPosZero();
   }
 }
+
+// For vector shift operation op, fold
+// (op x, (and y, ((1 << numbits(x)) - 1))) -> (target op x, y)
+static SDValue stripModuloOnShift(const TargetLowering &TLI, SDNode *N,
+                                  SelectionDAG &DAG) {
+  SDValue N0 = N->getOperand(0);
+  SDValue N1 = N->getOperand(1);
+  EVT VT = N0.getValueType();
+  unsigned OpSizeInBits = VT.getScalarSizeInBits();
+  unsigned Opcode = N->getOpcode();
+  unsigned TargetOpcode;
+
+  switch (Opcode) {
+  default:
+    llvm_unreachable("Unexpected shift operation");
+  case ISD::SHL:
+    TargetOpcode = PPCISD::SHL;
+    break;
+  case ISD::SRL:
+    TargetOpcode = PPCISD::SRL;
+    break;
+  case ISD::SRA:
+    TargetOpcode = PPCISD::SRA;
+    break;
+  }
+
+  if (VT.isVector() && TLI.isOperationLegal(Opcode, VT) &&
+      N1->getOpcode() == ISD::AND)
+    if (ConstantSDNode *Mask = isConstOrConstSplat(N1->getOperand(1)))
+      if (Mask->getZExtValue() == OpSizeInBits - 1)
+        return DAG.getNode(TargetOpcode, SDLoc(N), VT, N0, N1->getOperand(0));
+
+  return SDValue();
+}
+
+SDValue PPCTargetLowering::combineSHL(SDNode *N, DAGCombinerInfo &DCI) const {
+  if (auto Value = stripModuloOnShift(*this, N, DCI.DAG))
+    return Value;
+
+  return SDValue();
+}
+
+SDValue PPCTargetLowering::combineSRA(SDNode *N, DAGCombinerInfo &DCI) const {
+  if (auto Value = stripModuloOnShift(*this, N, DCI.DAG))
+    return Value;
+
+  return SDValue();
+}
+
+SDValue PPCTargetLowering::combineSRL(SDNode *N, DAGCombinerInfo &DCI) const {
+  if (auto Value = stripModuloOnShift(*this, N, DCI.DAG))
+    return Value;
+
+  return SDValue();
+}

diff --git a/lib/Target/PowerPC/PPCISelLowering.h b/lib/Target/PowerPC/PPCISelLowering.h
index d0793c7a3aeea62ddf68f3585e3f636d5d29ddeb..4fc7442572628e8935806fbea67e4a3344130379 100644 (file)
--- a/lib/Target/PowerPC/PPCISelLowering.h
+++ b/lib/Target/PowerPC/PPCISelLowering.h
@@ -117,9 +117,13 @@ namespace llvm {
       /// at function entry, used for PIC code.
       GlobalBaseReg,
 
-      /// These nodes represent the 32-bit PPC shifts that operate on 6-bit
-      /// shift amounts.  These nodes are generated by the multi-precision shift
-      /// code.
+      /// These nodes represent PPC shifts.
+      ///
+      /// For scalar types, only the last `n + 1` bits of the shift amounts
+      /// are used, where n is log2(sizeof(element) * 8). See sld/slw, etc.
+      /// for exact behaviors.
+      ///
+      /// For vector types, only the last n bits are used. See vsld.
       SRL, SRA, SHL,
 
       /// The combination of sra[wd]i and addze used to implemented signed
@@ -999,6 +1003,9 @@ namespace llvm {
     SDValue DAGCombineBuildVector(SDNode *N, DAGCombinerInfo &DCI) const;
     SDValue DAGCombineTruncBoolExt(SDNode *N, DAGCombinerInfo &DCI) const;
     SDValue combineFPToIntToFP(SDNode *N, DAGCombinerInfo &DCI) const;
+    SDValue combineSHL(SDNode *N, DAGCombinerInfo &DCI) const;
+    SDValue combineSRA(SDNode *N, DAGCombinerInfo &DCI) const;
+    SDValue combineSRL(SDNode *N, DAGCombinerInfo &DCI) const;
 
     /// ConvertSETCCToSubtract - looks at SETCC that compares ints. It replaces
     /// SETCC with integer subtraction when (1) there is a legal way of doing it
@@ -1017,14 +1024,6 @@ namespace llvm {
     SDValue
     combineElementTruncationToVectorTruncation(SDNode *N,
                                                DAGCombinerInfo &DCI) const;
-
-    bool supportsModuloShift(ISD::NodeType Inst,
-                             EVT ReturnType) const override {
-      assert((Inst == ISD::SHL || Inst == ISD::SRA || Inst == ISD::SRL) &&
-             "Expect a shift instruction");
-      assert(isOperationLegal(Inst, ReturnType));
-      return ReturnType.isVector();
-    }
   };
 
   namespace PPC {

diff --git a/lib/Target/PowerPC/PPCInstrAltivec.td b/lib/Target/PowerPC/PPCInstrAltivec.td
index c380766e9f5c44f9f86c0ad097e335f0d5412a03..e14d18fd54331bd2a3ccf96a1c22be43ca21a643 100644 (file)
--- a/lib/Target/PowerPC/PPCInstrAltivec.td
+++ b/lib/Target/PowerPC/PPCInstrAltivec.td
@@ -987,6 +987,12 @@ def : Pat<(v8i16 (shl v8i16:$vA, v8i16:$vB)),
           (v8i16 (VSLH $vA, $vB))>;
 def : Pat<(v4i32 (shl v4i32:$vA, v4i32:$vB)),
           (v4i32 (VSLW $vA, $vB))>;
+def : Pat<(v16i8 (PPCshl v16i8:$vA, v16i8:$vB)),
+          (v16i8 (VSLB $vA, $vB))>;
+def : Pat<(v8i16 (PPCshl v8i16:$vA, v8i16:$vB)),
+          (v8i16 (VSLH $vA, $vB))>;
+def : Pat<(v4i32 (PPCshl v4i32:$vA, v4i32:$vB)),
+          (v4i32 (VSLW $vA, $vB))>;
 
 def : Pat<(v16i8 (srl v16i8:$vA, v16i8:$vB)),
           (v16i8 (VSRB $vA, $vB))>;
@@ -994,6 +1000,12 @@ def : Pat<(v8i16 (srl v8i16:$vA, v8i16:$vB)),
           (v8i16 (VSRH $vA, $vB))>;
 def : Pat<(v4i32 (srl v4i32:$vA, v4i32:$vB)),
           (v4i32 (VSRW $vA, $vB))>;
+def : Pat<(v16i8 (PPCsrl v16i8:$vA, v16i8:$vB)),
+          (v16i8 (VSRB $vA, $vB))>;
+def : Pat<(v8i16 (PPCsrl v8i16:$vA, v8i16:$vB)),
+          (v8i16 (VSRH $vA, $vB))>;
+def : Pat<(v4i32 (PPCsrl v4i32:$vA, v4i32:$vB)),
+          (v4i32 (VSRW $vA, $vB))>;
 
 def : Pat<(v16i8 (sra v16i8:$vA, v16i8:$vB)),
           (v16i8 (VSRAB $vA, $vB))>;
@@ -1001,6 +1013,12 @@ def : Pat<(v8i16 (sra v8i16:$vA, v8i16:$vB)),
           (v8i16 (VSRAH $vA, $vB))>;
 def : Pat<(v4i32 (sra v4i32:$vA, v4i32:$vB)),
           (v4i32 (VSRAW $vA, $vB))>;
+def : Pat<(v16i8 (PPCsra v16i8:$vA, v16i8:$vB)),
+          (v16i8 (VSRAB $vA, $vB))>;
+def : Pat<(v8i16 (PPCsra v8i16:$vA, v8i16:$vB)),
+          (v8i16 (VSRAH $vA, $vB))>;
+def : Pat<(v4i32 (PPCsra v4i32:$vA, v4i32:$vB)),
+          (v4i32 (VSRAW $vA, $vB))>;
 
 // Float to integer and integer to float conversions
 def : Pat<(v4i32 (fp_to_sint v4f32:$vA)),
@@ -1072,14 +1090,24 @@ def:Pat<(vmrgow_swapped_shuffle v16i8:$vA, v16i8:$vB),
 // Vector shifts
 def VRLD : VX1_Int_Ty<196, "vrld", int_ppc_altivec_vrld, v2i64>;
 def VSLD : VXForm_1<1476, (outs vrrc:$vD), (ins vrrc:$vA, vrrc:$vB),
-                    "vsld $vD, $vA, $vB", IIC_VecGeneral,
-                    [(set v2i64:$vD, (shl v2i64:$vA, v2i64:$vB))]>;
+                    "vsld $vD, $vA, $vB", IIC_VecGeneral, []>;
 def VSRD : VXForm_1<1732, (outs vrrc:$vD), (ins vrrc:$vA, vrrc:$vB),
-                   "vsrd $vD, $vA, $vB", IIC_VecGeneral,
-                   [(set v2i64:$vD, (srl v2i64:$vA, v2i64:$vB))]>;
+                   "vsrd $vD, $vA, $vB", IIC_VecGeneral, []>;
 def VSRAD : VXForm_1<964, (outs vrrc:$vD), (ins vrrc:$vA, vrrc:$vB),
-                    "vsrad $vD, $vA, $vB", IIC_VecGeneral,
-                    [(set v2i64:$vD, (sra v2i64:$vA, v2i64:$vB))]>;
+                    "vsrad $vD, $vA, $vB", IIC_VecGeneral, []>;
+
+def : Pat<(v2i64 (shl v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSLD $vA, $vB))>;
+def : Pat<(v2i64 (PPCshl v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSLD $vA, $vB))>;
+def : Pat<(v2i64 (srl v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSRD $vA, $vB))>;
+def : Pat<(v2i64 (PPCsrl v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSRD $vA, $vB))>;
+def : Pat<(v2i64 (sra v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSRAD $vA, $vB))>;
+def : Pat<(v2i64 (PPCsra v2i64:$vA, v2i64:$vB)),
+          (v2i64 (VSRAD $vA, $vB))>;
 
 // Vector Integer Arithmetic Instructions
 let isCommutable = 1 in {