GlobalISel: add code to widen scalar G_ADD

llvm-svn: 277747

3 files changed, 39 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 5e737d5e2bb..09a8fa6001b 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -119,6 +119,11 @@ MachineInstrBuilder MachineIRBuilder::buildStore(LLT VTy, LLT PTy,
       .addMemOperand(&MMO);
 }
 
+MachineInstrBuilder MachineIRBuilder::buildAnyExtend(LLT Ty, unsigned Res,
+                                                     unsigned Op) {
+  return buildInstr(TargetOpcode::G_ANYEXTEND, Ty).addDef(Res).addUse(Op);
+}
+
 MachineInstrBuilder
 MachineIRBuilder::buildExtract(LLT Ty, ArrayRef<unsigned> Results, unsigned Src,
                                ArrayRef<unsigned> Indexes) {
@@ -157,3 +162,8 @@ MachineInstrBuilder MachineIRBuilder::buildIntrinsic(ArrayRef<LLT> Tys,
   MIB.addIntrinsicID(ID);
   return MIB;
 }
+
+MachineInstrBuilder MachineIRBuilder::buildTrunc(LLT Ty, unsigned Res,
+                                           unsigned Op) {
+  return buildInstr(TargetOpcode::G_TRUNC, Ty).addDef(Res).addUse(Op);
+}
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp b/llvm/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
index 55adbbd20ce..71d3206dc55 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
@@ -66,7 +66,30 @@ MachineLegalizeHelper::narrowScalar(MachineInstr &MI, LLT NarrowTy) {
 
 MachineLegalizeHelper::LegalizeResult
 MachineLegalizeHelper::widenScalar(MachineInstr &MI, LLT WideTy) {
-  return UnableToLegalize;
+  switch (MI.getOpcode()) {
+  default:
+    return UnableToLegalize;
+  case TargetOpcode::G_ADD: {
+    // Perform operation at larger width (any extension is fine here, high bits
+    // don't affect the result) and then truncate the result back to the
+    // original type.
+    unsigned WideSize = WideTy.getSizeInBits();
+
+    MIRBuilder.setInstr(MI);
+
+    unsigned Src1Ext = MRI.createGenericVirtualRegister(WideSize);
+    unsigned Src2Ext = MRI.createGenericVirtualRegister(WideSize);
+    MIRBuilder.buildAnyExtend(WideTy, Src1Ext, MI.getOperand(1).getReg());
+    MIRBuilder.buildAnyExtend(WideTy, Src2Ext, MI.getOperand(2).getReg());
+
+    unsigned DstExt = MRI.createGenericVirtualRegister(WideSize);
+    MIRBuilder.buildAdd(WideTy, DstExt, Src1Ext, Src2Ext);
+
+    MIRBuilder.buildTrunc(MI.getType(), MI.getOperand(0).getReg(), DstExt);
+    MI.eraseFromParent();
+    return Legalized;
+  }
+  }
 }
 
 MachineLegalizeHelper::LegalizeResult
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp b/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp
index 6856ed57a0b..881b5026fa6 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp
@@ -25,6 +25,11 @@
 using namespace llvm;
 
 MachineLegalizer::MachineLegalizer() : TablesInitialized(false) {
+  // FIXME: these two can be legalized to the fundamental load/store Jakob
+  // proposed. Once loads & stores are supported.
+  DefaultActions[TargetOpcode::G_ANYEXTEND] = Legal;
+  DefaultActions[TargetOpcode::G_TRUNC] = Legal;
+
   DefaultActions[TargetOpcode::G_ADD] = NarrowScalar;
 }