commit c2d5e6d63774c5d015c7b5e1b6822d854e1ac465
author Tim Northover <tnorthover@apple.com> Mon Jun 26 20:34:13 2017 +0000
committer Tim Northover <tnorthover@apple.com> Mon Jun 26 20:34:13 2017 +0000
tree b620d740100fbf0d9da4e3ffa5c00383466f167e
parent f6766bd2464bd5e405c5450cfa9daad7035d0ddb

AArch64: legalize G_EXTRACT operations.

This is the dual problem to legalizing G_INSERTs so most of the code and
testing was cribbed from there.

llvm-svn: 306328

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 1d0d3df..1218232 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -158,7 +158,7 @@
                                                               unsigned TypeIdx,
                                                               LLT NarrowTy) {
   // FIXME: Don't know how to handle secondary types yet.
-  if (TypeIdx != 0)
+  if (TypeIdx != 0 && MI.getOpcode() != TargetOpcode::G_EXTRACT)
     return UnableToLegalize;
 
   MIRBuilder.setInstr(MI);
@@ -193,6 +193,58 @@
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_EXTRACT: {
+    if (TypeIdx != 1)
+      return UnableToLegalize;
+
+    int64_t NarrowSize = NarrowTy.getSizeInBits();
+    int NumParts =
+        MRI.getType(MI.getOperand(1).getReg()).getSizeInBits() / NarrowSize;
+
+    SmallVector<unsigned, 2> SrcRegs, DstRegs;
+    SmallVector<uint64_t, 2> Indexes;
+    extractParts(MI.getOperand(1).getReg(), NarrowTy, NumParts, SrcRegs);
+
+    unsigned OpReg = MI.getOperand(0).getReg();
+    int64_t OpStart = MI.getOperand(2).getImm();
+    int64_t OpSize = MRI.getType(OpReg).getSizeInBits();
+    for (int i = 0; i < NumParts; ++i) {
+      unsigned SrcStart = i * NarrowSize;
+
+      if (SrcStart + NarrowSize <= OpStart || SrcStart >= OpStart + OpSize) {
+        // No part of the extract uses this subregister, ignore it.
+        continue;
+      } else if (SrcStart == OpStart && NarrowTy == MRI.getType(OpReg)) {
+        // The entire subregister is extracted, forward the value.
+        DstRegs.push_back(SrcRegs[i]);
+        continue;
+      }
+
+      // OpSegStart is where this destination segment would start in OpReg if it
+      // extended infinitely in both directions.
+      int64_t ExtractOffset, SegSize;
+      if (OpStart < SrcStart) {
+        ExtractOffset = 0;
+        SegSize = std::min(NarrowSize, OpStart + OpSize - SrcStart);
+      } else {
+        ExtractOffset = OpStart - SrcStart;
+        SegSize = std::min(SrcStart + NarrowSize - OpStart, OpSize);
+      }
+
+      unsigned SegReg = SrcRegs[i];
+      if (ExtractOffset != 0 || SegSize != NarrowSize) {
+        // A genuine extract is needed.
+        SegReg = MRI.createGenericVirtualRegister(LLT::scalar(SegSize));
+        MIRBuilder.buildExtract(SegReg, SrcRegs[i], ExtractOffset);
+      }
+
+      DstRegs.push_back(SegReg);
+    }
+
+    MIRBuilder.buildMerge(MI.getOperand(0).getReg(), DstRegs);
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_INSERT: {
     if (TypeIdx != 0)
       return UnableToLegalize;

llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
index 595802f..ef1ce7f 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
@@ -42,6 +42,7 @@
 
   DefaultActions[TargetOpcode::G_BRCOND] = WidenScalar;
   DefaultActions[TargetOpcode::G_INSERT] = NarrowScalar;
+  DefaultActions[TargetOpcode::G_EXTRACT] = NarrowScalar;
   DefaultActions[TargetOpcode::G_FNEG] = Lower;
 }
 
@@ -75,8 +76,7 @@
 
   // FIXME: the long-term plan calls for expansion in terms of load/store (if
   // they're not legal).
-  if (Aspect.Opcode == TargetOpcode::G_EXTRACT ||
-      Aspect.Opcode == TargetOpcode::G_MERGE_VALUES ||
+  if (Aspect.Opcode == TargetOpcode::G_MERGE_VALUES ||
       Aspect.Opcode == TargetOpcode::G_UNMERGE_VALUES)
     return std::make_pair(Legal, Aspect.Type);
 

llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 3c70013..6fcc390 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -482,6 +482,9 @@
          "input operands do not cover output register");
 #endif
 
+  if (Ops.size() == 1)
+    return buildCopy(Res, Ops[0]);
+
   MachineInstrBuilder MIB = buildInstr(TargetOpcode::G_MERGE_VALUES);
   MIB.addDef(Res);
   for (unsigned i = 0; i < Ops.size(); ++i)