2 files changed, 55 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMLegalizerInfo.cpp b/llvm/lib/Target/ARM/ARMLegalizerInfo.cpp
index d1c5d964d95..9b86030fdd2 100644
--- a/llvm/lib/Target/ARM/ARMLegalizerInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMLegalizerInfo.cpp
@@ -13,6 +13,8 @@
 
 #include "ARMLegalizerInfo.h"
 #include "ARMSubtarget.h"
+#include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Type.h"
@@ -48,6 +50,11 @@ ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) {
       setAction({Op, Ty}, Legal);
 
   for (unsigned Op : {G_SDIV, G_UDIV}) {
+    for (auto Ty : {s8, s16})
+      // FIXME: We need WidenScalar here, but in the case of targets with
+      // software division we'll also need Libcall afterwards. Treat as Custom
+      // until we have better support for chaining legalization actions.
+      setAction({Op, Ty}, Custom);
     if (ST.hasDivideInARMMode())
       setAction({Op, s32}, Legal);
     else
@@ -82,3 +89,48 @@ ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) {
 
   computeTables();
 }
+
+bool ARMLegalizerInfo::legalizeCustom(MachineInstr &MI,
+                                      MachineRegisterInfo &MRI,
+                                      MachineIRBuilder &MIRBuilder) const {
+  using namespace TargetOpcode;
+
+  switch (MI.getOpcode()) {
+  default:
+    return false;
+  case G_SDIV:
+  case G_UDIV: {
+    LLT Ty = MRI.getType(MI.getOperand(0).getReg());
+    if (Ty != LLT::scalar(16) && Ty != LLT::scalar(8))
+      return false;
+
+    // We need to widen to 32 bits and then maybe, if the target requires,
+    // transform into a libcall.
+    LegalizerHelper Helper(MIRBuilder.getMF());
+
+    MachineInstr *NewMI = nullptr;
+    Helper.MIRBuilder.recordInsertions([&](MachineInstr *MI) {
+      // Store the new, 32-bit div instruction.
+      if (MI->getOpcode() == G_SDIV || MI->getOpcode() == G_UDIV)
+        NewMI = MI;
+    });
+
+    auto Result = Helper.widenScalar(MI, 0, LLT::scalar(32));
+    Helper.MIRBuilder.stopRecordingInsertions();
+    if (Result == LegalizerHelper::UnableToLegalize) {
+      return false;
+    }
+    assert(NewMI && "Couldn't find widened instruction");
+    assert((NewMI->getOpcode() == G_SDIV || NewMI->getOpcode() == G_UDIV) &&
+           "Unexpected widened instruction");
+    assert(MRI.getType(NewMI->getOperand(0).getReg()).getSizeInBits() == 32 &&
+           "Unexpected type for the widened instruction");
+
+    Result = Helper.legalizeInstrStep(*NewMI);
+    if (Result == LegalizerHelper::UnableToLegalize) {
+      return false;
+    }
+    return true;
+  }
+  }
+}
diff --git a/llvm/lib/Target/ARM/ARMLegalizerInfo.h b/llvm/lib/Target/ARM/ARMLegalizerInfo.h
index 0b8a608a6bd..a9bdd367737 100644
--- a/llvm/lib/Target/ARM/ARMLegalizerInfo.h
+++ b/llvm/lib/Target/ARM/ARMLegalizerInfo.h
@@ -24,6 +24,9 @@ class ARMSubtarget;
 class ARMLegalizerInfo : public LegalizerInfo {
 public:
   ARMLegalizerInfo(const ARMSubtarget &ST);
+
+  bool legalizeCustom(MachineInstr &MI, MachineRegisterInfo &MRI,
+                      MachineIRBuilder &MIRBuilder) const override;
 };
 } // End llvm namespace.
 #endif