GlobalISel: support translating select instructions.

llvm-svn: 279309

include/llvm/CodeGen/GlobalISel/IRTranslator.h

@@ -153,6 +153,8 @@ private:
 
   bool translateInsertValue(const User &U);
 
+  bool translateSelect(const User &U);
+
   /// Translate return (ret) instruction.
   /// The target needs to implement CallLowering::lowerReturn for
   /// this to succeed.
@@ -263,7 +265,6 @@ private:
   bool translateCleanupPad(const User &U) { return false; }
   bool translateCatchPad(const User &U) { return false; }
   bool translateFCmp(const User &U) { return false; }
-  bool translateSelect(const User &U) { return false; }
   bool translateUserOp1(const User &U) { return false; }
   bool translateUserOp2(const User &U) { return false; }
   bool translateVAArg(const User &U) { return false; }

include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h

@@ -301,13 +301,21 @@ public:
   /// \return The newly created instruction.
   MachineInstrBuilder buildTrunc(LLT Ty, unsigned Res, unsigned Op);
 
-  /// Build and insert either a G_ICMP
+  /// Build and insert a G_ICMP
   ///
   /// \pre setBasicBlock or setMI must have been called.
   ///
   /// \return a MachineInstrBuilder for the newly created instruction.
   MachineInstrBuilder buildICmp(ArrayRef<LLT> Tys, CmpInst::Predicate Pred,
                                 unsigned Res, unsigned Op0, unsigned Op1);
+
+  /// Build and insert a \p Res = G_SELECT { \p Ty, s1 } \p Tst, \p Op0, \p Op1
+  ///
+  /// \pre setBasicBlock or setMI must have been called.
+  ///
+  /// \return a MachineInstrBuilder for the newly created instruction.
+  MachineInstrBuilder buildSelect(LLT Ty, unsigned Res, unsigned Tst,
+                                  unsigned Op0, unsigned Op1);
 };
 
 } // End namespace llvm.

include/llvm/Target/GenericOpcodes.td

@@ -191,6 +191,13 @@ def G_ICMP : Instruction {
   let hasSideEffects = 0;
 }
 
+// Generic select
+def G_SELECT : Instruction {
+  let OutOperandList = (outs unknown:$dst);
+  let InOperandList = (ins unknown:$tst, unknown:$src1, unknown:$src2);
+  let hasSideEffects = 0;
+}
+
 //------------------------------------------------------------------------------
 // Overflow ops
 //------------------------------------------------------------------------------

include/llvm/Target/TargetOpcodes.def

@@ -262,6 +262,9 @@ HANDLE_TARGET_OPCODE(G_ASHR)
 /// Generic integer-base comparison, also applicable to vectors of integers.
 HANDLE_TARGET_OPCODE(G_ICMP)
 
+/// Generic select.
+HANDLE_TARGET_OPCODE(G_SELECT)
+
 /// Generic unsigned add instruction, consuming the normal operands plus a carry
 /// flag, and similarly producing the result and a carry flag.
 HANDLE_TARGET_OPCODE(G_UADDE)

lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -236,6 +236,13 @@ bool IRTranslator::translateInsertValue(const User &U) {
   return true;
 }
 
+bool IRTranslator::translateSelect(const User &U) {
+  MIRBuilder.buildSelect(
+      LLT{*U.getType()}, getOrCreateVReg(U), getOrCreateVReg(*U.getOperand(0)),
+      getOrCreateVReg(*U.getOperand(1)), getOrCreateVReg(*U.getOperand(2)));
+  return true;
+}
+
 bool IRTranslator::translateBitCast(const User &U) {
   if (LLT{*U.getOperand(0)->getType()} == LLT{*U.getType()}) {
     unsigned &Reg = ValToVReg[&U];

lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

@@ -216,3 +216,13 @@ MachineInstrBuilder MachineIRBuilder::buildICmp(ArrayRef<LLT> Tys,
       .addUse(Op0)
       .addUse(Op1);
 }
+
+MachineInstrBuilder MachineIRBuilder::buildSelect(LLT Ty, unsigned Res,
+                                                  unsigned Tst,
+                                                  unsigned Op0, unsigned Op1) {
+  return buildInstr(TargetOpcode::G_SELECT, {Ty, LLT::scalar(1)})
+      .addDef(Res)
+      .addUse(Tst)
+      .addUse(Op0)
+      .addUse(Op1);
+}

test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll

@@ -729,3 +729,14 @@ define void @test_insertvalue_agg(%struct.nested* %addr, {i8, i32}* %addr2) {
   store %struct.nested %res, %struct.nested* %addr
   ret void
 }
+
+; CHECK-LABEL: name: test_select
+; CHECK: [[TST:%[0-9]+]](1) = COPY %w0
+; CHECK: [[LHS:%[0-9]+]](32) = COPY %w1
+; CHECK: [[RHS:%[0-9]+]](32) = COPY %w2
+; CHECK: [[RES:%[0-9]+]](32) = G_SELECT { s32, s1 } [[TST]], [[LHS]], [[RHS]]
+; CHECK: %w0 = COPY [[RES]]
+define i32 @test_select(i1 %tst, i32 %lhs, i32 %rhs) {
+  %res = select i1 %tst, i32 %lhs, i32 %rhs
+  ret i32 %res
+}