GlobalISel/InstructionSelector: Implement GIR_CopyFConstantAsFPImm

Summary: AMDGPU will need this to enable the TableGen'd GlobalISel selector.

Reviewers: dsanders, aditya_nandakumar

Reviewed By: dsanders

Subscribers: rovka, kristof.beyls, tpr, llvm-commits

Differential Revision: https://reviews.llvm.org/D45990

llvm-svn: 331579

2 files changed, 23 insertions, 0 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
index 90e213f750d..1dee6d12484 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
@@ -248,6 +248,12 @@ enum {
   /// The operand index is implicitly 1.
   GIR_CopyConstantAsSImm,
 
+  /// Render a G_FCONSTANT operator as a sign-extended immediate.
+  /// - NewInsnID - Instruction ID to modify
+  /// - OldInsnID - Instruction ID to copy from
+  /// The operand index is implicitly 1.
+  GIR_CopyFConstantAsFPImm,
+
   /// Constrain an instruction operand to a register class.
   /// - InsnID - Instruction ID to modify
   /// - OpIdx - Operand index
diff --git a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
index f7593ba6ef2..415ae74ed7f 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
@@ -662,6 +662,23 @@ bool InstructionSelector::executeMatchTable(
       break;
     }
 
+    // TODO: Needs a test case once we have a pattern that uses this.
+    case GIR_CopyFConstantAsFPImm: {
+      int64_t NewInsnID = MatchTable[CurrentIdx++];
+      int64_t OldInsnID = MatchTable[CurrentIdx++];
+      assert(OutMIs[NewInsnID] && "Attempted to add to undefined instruction");
+      assert(State.MIs[OldInsnID]->getOpcode() == TargetOpcode::G_FCONSTANT && "Expected G_FCONSTANT");
+      if (State.MIs[OldInsnID]->getOperand(1).isFPImm())
+        OutMIs[NewInsnID].addFPImm(
+            State.MIs[OldInsnID]->getOperand(1).getFPImm());
+      else
+        llvm_unreachable("Expected FPImm operand");
+      DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
+                      dbgs() << CurrentIdx << ": GIR_CopyFPConstantAsFPImm(OutMIs["
+                             << NewInsnID << "], MIs[" << OldInsnID << "])\n");
+      break;
+    }
+
     case GIR_CustomRenderer: {
       int64_t InsnID = MatchTable[CurrentIdx++];
       int64_t OldInsnID = MatchTable[CurrentIdx++];