GlobalISel: add merge/unmerge nodes for legalization.

These are simplified variants of the current G_SEQUENCE and G_EXTRACT, which
assume the individual parts will be contiguous, homogeneous, and occupy the
entirity of the larger register. This makes reasoning about them much easer
since you only have to look at the first register being merged and the result
to know what the instruction is doing.

I intend to gradually replace all uses of the more complicated sequence/extract
with these (or single-element insert/extracts), and then remove the older
variants. For now we start with legalization.

llvm-svn: 296921

1 files changed, 6 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 6bb64e068ec..2d28a42c797 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -86,13 +86,9 @@ LegalizerHelper::legalizeInstr(MachineInstr &MI,
 
 void LegalizerHelper::extractParts(unsigned Reg, LLT Ty, int NumParts,
                                    SmallVectorImpl<unsigned> &VRegs) {
-  unsigned Size = Ty.getSizeInBits();
-  SmallVector<uint64_t, 4> Indexes;
-  for (int i = 0; i < NumParts; ++i) {
+  for (int i = 0; i < NumParts; ++i)
     VRegs.push_back(MRI.createGenericVirtualRegister(Ty));
-    Indexes.push_back(i * Size);
-  }
-  MIRBuilder.buildExtract(VRegs, Indexes, Reg);
+  MIRBuilder.buildUnmerge(VRegs, Reg);
 }
 
 static RTLIB::Libcall getRTLibDesc(unsigned Opcode, unsigned Size) {
@@ -156,12 +152,10 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
     return UnableToLegalize;
   case TargetOpcode::G_ADD: {
     // Expand in terms of carry-setting/consuming G_ADDE instructions.
-    unsigned NarrowSize = NarrowTy.getSizeInBits();
     int NumParts = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits() /
                    NarrowTy.getSizeInBits();
 
     SmallVector<unsigned, 2> Src1Regs, Src2Regs, DstRegs;
-    SmallVector<uint64_t, 2> Indexes;
     extractParts(MI.getOperand(1).getReg(), NarrowTy, NumParts, Src1Regs);
     extractParts(MI.getOperand(2).getReg(), NarrowTy, NumParts, Src2Regs);
 
@@ -176,11 +170,10 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
                             Src2Regs[i], CarryIn);
 
       DstRegs.push_back(DstReg);
-      Indexes.push_back(i * NarrowSize);
       CarryIn = CarryOut;
     }
     unsigned DstReg = MI.getOperand(0).getReg();
-    MIRBuilder.buildSequence(DstReg, DstRegs, Indexes);
+    MIRBuilder.buildMerge(DstReg, DstRegs);
     MI.eraseFromParent();
     return Legalized;
   }
@@ -200,7 +193,6 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
     for (int i = 0; i < NumParts; ++i) {
       unsigned DstStart = i * NarrowSize;
       unsigned DstReg = MRI.createGenericVirtualRegister(NarrowTy);
-      Indexes.push_back(DstStart);
 
       findInsertionsForRange(DstStart, DstStart + NarrowSize, CurOp, EndOp, MI);
 
@@ -239,7 +231,7 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
     }
 
     assert(DstRegs.size() == (unsigned)NumParts && "not all parts covered");
-    MIRBuilder.buildSequence(MI.getOperand(0).getReg(), DstRegs, Indexes);
+    MIRBuilder.buildMerge(MI.getOperand(0).getReg(), DstRegs);
     MI.eraseFromParent();
     return Legalized;
   }
@@ -251,7 +243,6 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
         MRI.getType(MI.getOperand(1).getReg()).getAddressSpace(), NarrowSize);
 
     SmallVector<unsigned, 2> DstRegs;
-    SmallVector<uint64_t, 2> Indexes;
     for (int i = 0; i < NumParts; ++i) {
       unsigned DstReg = MRI.createGenericVirtualRegister(NarrowTy);
       unsigned SrcReg = MRI.createGenericVirtualRegister(NarrowPtrTy);
@@ -264,10 +255,9 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
       MIRBuilder.buildLoad(DstReg, SrcReg, **MI.memoperands_begin());
 
       DstRegs.push_back(DstReg);
-      Indexes.push_back(i * NarrowSize);
     }
     unsigned DstReg = MI.getOperand(0).getReg();
-    MIRBuilder.buildSequence(DstReg, DstRegs, Indexes);
+    MIRBuilder.buildMerge(DstReg, DstRegs);
     MI.eraseFromParent();
     return Legalized;
   }
@@ -578,7 +568,6 @@ LegalizerHelper::fewerElementsVector(MachineInstr &MI, unsigned TypeIdx,
     MIRBuilder.setInstr(MI);
 
     SmallVector<unsigned, 2> Src1Regs, Src2Regs, DstRegs;
-    SmallVector<uint64_t, 2> Indexes;
     extractParts(MI.getOperand(1).getReg(), NarrowTy, NumParts, Src1Regs);
     extractParts(MI.getOperand(2).getReg(), NarrowTy, NumParts, Src2Regs);
 
@@ -586,10 +575,9 @@ LegalizerHelper::fewerElementsVector(MachineInstr &MI, unsigned TypeIdx,
       unsigned DstReg = MRI.createGenericVirtualRegister(NarrowTy);
       MIRBuilder.buildAdd(DstReg, Src1Regs[i], Src2Regs[i]);
       DstRegs.push_back(DstReg);
-      Indexes.push_back(i * NarrowSize);
     }
 
-    MIRBuilder.buildSequence(DstReg, DstRegs, Indexes);
+    MIRBuilder.buildMerge(DstReg, DstRegs);
     MI.eraseFromParent();
     return Legalized;
   }