[AVR] Expand 8/16-bit multiplication to libcalls on MCUs that don't have hardware MUL

This change modifies the LLVM ISel lowering settings so that
8-bit/16-bit multiplication is expanded to calls into the compiler
runtime library if the MCU being targeted does not support
multiplication in hardware.

Before this, MUL instructions would be generated on CPUs like the
ATtiny85, triggering a CPU reset due to an illegal instruction at
runtime.

First raised in https://github.com/avr-rust/rust/issues/124.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351523 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AVR/AVRISelLowering.cpp b/lib/Target/AVR/AVRISelLowering.cpp
index 57fc978b54bb61aec6ee39e867d549200239054e..5db7577823226b640e575e89b32a6471ae7cfc6f 100644 (file)
--- a/lib/Target/AVR/AVRISelLowering.cpp
+++ b/lib/Target/AVR/AVRISelLowering.cpp
@@ -26,19 +26,21 @@
 
 #include "AVR.h"
 #include "AVRMachineFunctionInfo.h"
+#include "AVRSubtarget.h"
 #include "AVRTargetMachine.h"
 #include "MCTargetDesc/AVRMCTargetDesc.h"
 
 namespace llvm {
 
-AVRTargetLowering::AVRTargetLowering(AVRTargetMachine &tm)
-    : TargetLowering(tm) {
+AVRTargetLowering::AVRTargetLowering(const AVRTargetMachine &TM,
+                                     const AVRSubtarget &STI)
+    : TargetLowering(TM), Subtarget(STI) {
   // Set up the register classes.
   addRegisterClass(MVT::i8, &AVR::GPR8RegClass);
   addRegisterClass(MVT::i16, &AVR::DREGSRegClass);
 
   // Compute derived properties from the register classes.
-  computeRegisterProperties(tm.getSubtargetImpl()->getRegisterInfo());
+  computeRegisterProperties(Subtarget.getRegisterInfo());
 
   setBooleanContents(ZeroOrOneBooleanContent);
   setBooleanVectorContents(ZeroOrOneBooleanContent);
@@ -163,6 +165,13 @@ AVRTargetLowering::AVRTargetLowering(AVRTargetMachine &tm)
   setOperationAction(ISD::SMUL_LOHI, MVT::i16, Expand);
   setOperationAction(ISD::UMUL_LOHI, MVT::i16, Expand);
 
+  // Expand multiplications to libcalls when there is
+  // no hardware MUL.
+  if (!Subtarget.supportsMultiplication()) {
+    setOperationAction(ISD::SMUL_LOHI, MVT::i8, Expand);
+    setOperationAction(ISD::UMUL_LOHI, MVT::i8, Expand);
+  }
+
   for (MVT VT : MVT::integer_valuetypes()) {
     setOperationAction(ISD::MULHS, VT, Expand);
     setOperationAction(ISD::MULHU, VT, Expand);
@@ -1271,7 +1280,7 @@ SDValue AVRTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
 
   // Add a register mask operand representing the call-preserved registers.
   const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
-  const TargetRegisterInfo *TRI = TM.getSubtargetImpl()->getRegisterInfo();
+  const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
   const uint32_t *Mask =
       TRI->getCallPreservedMask(DAG.getMachineFunction(), CallConv);
   assert(Mask && "Missing call preserved mask for calling convention");
@@ -1434,7 +1443,7 @@ MachineBasicBlock *AVRTargetLowering::insertShift(MachineInstr &MI,
   MachineFunction *F = BB->getParent();
   MachineRegisterInfo &RI = F->getRegInfo();
   const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
-  const TargetInstrInfo &TII = *TM.getSubtargetImpl()->getInstrInfo();
+  const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
   DebugLoc dl = MI.getDebugLoc();
 
   switch (MI.getOpcode()) {
@@ -1575,7 +1584,7 @@ static bool isCopyMulResult(MachineBasicBlock::iterator const &I) {
 MachineBasicBlock *AVRTargetLowering::insertMul(MachineInstr &MI,
                                                 MachineBasicBlock *BB) const {
   const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
-  const TargetInstrInfo &TII = *TM.getSubtargetImpl()->getInstrInfo();
+  const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
   MachineBasicBlock::iterator I(MI);
   ++I; // in any case insert *after* the mul instruction
   if (isCopyMulResult(I))
@@ -1838,9 +1847,6 @@ std::pair<unsigned, const TargetRegisterClass *>
 AVRTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                                 StringRef Constraint,
                                                 MVT VT) const {
-  auto STI = static_cast<const AVRTargetMachine &>(this->getTargetMachine())
-                 .getSubtargetImpl();
-
   // We only support i8 and i16.
   //
   //:FIXME: remove this assert for now since it gets sometimes executed
@@ -1884,8 +1890,8 @@ AVRTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
     }
   }
 
-  return TargetLowering::getRegForInlineAsmConstraint(STI->getRegisterInfo(),
-                                                      Constraint, VT);
+  return TargetLowering::getRegForInlineAsmConstraint(
+      Subtarget.getRegisterInfo(), Constraint, VT);
 }
 
 void AVRTargetLowering::LowerAsmOperandForConstraint(SDValue Op,

diff --git a/lib/Target/AVR/AVRISelLowering.h b/lib/Target/AVR/AVRISelLowering.h
index c90c65c81f700672bf9e089c95929156a7ca9c52..7d77dd8fb01880f26337c967c9ad710c9c336a1e 100644 (file)
--- a/lib/Target/AVR/AVRISelLowering.h
+++ b/lib/Target/AVR/AVRISelLowering.h
@@ -64,12 +64,14 @@ enum NodeType {
 
 } // end of namespace AVRISD
 
+class AVRSubtarget;
 class AVRTargetMachine;
 
 /// Performs target lowering for the AVR.
 class AVRTargetLowering : public TargetLowering {
 public:
-  explicit AVRTargetLowering(AVRTargetMachine &TM);
+  explicit AVRTargetLowering(const AVRTargetMachine &TM,
+                             const AVRSubtarget &STI);
 
 public:
   MVT getScalarShiftAmountTy(const DataLayout &, EVT LHSTy) const override {
@@ -164,6 +166,10 @@ private:
                           const SDLoc &dl, SelectionDAG &DAG,
                           SmallVectorImpl<SDValue> &InVals) const;
 
+protected:
+
+  const AVRSubtarget &Subtarget;
+
 private:
   MachineBasicBlock *insertShift(MachineInstr &MI, MachineBasicBlock *BB) const;
   MachineBasicBlock *insertMul(MachineInstr &MI, MachineBasicBlock *BB) const;

diff --git a/lib/Target/AVR/AVRSubtarget.cpp b/lib/Target/AVR/AVRSubtarget.cpp
index 556d69ec523413ef2e9926142cac1c7f3b73387d..c7c566270f4329ebfdd5e0584c432e036d27719a 100644 (file)
--- a/lib/Target/AVR/AVRSubtarget.cpp
+++ b/lib/Target/AVR/AVRSubtarget.cpp
@@ -29,9 +29,9 @@
 namespace llvm {
 
 AVRSubtarget::AVRSubtarget(const Triple &TT, const std::string &CPU,
-                           const std::string &FS, AVRTargetMachine &TM)
+                           const std::string &FS, const AVRTargetMachine &TM)
     : AVRGenSubtargetInfo(TT, CPU, FS), InstrInfo(), FrameLowering(),
-      TLInfo(TM), TSInfo(),
+      TLInfo(TM, initializeSubtargetDependencies(CPU, FS, TM)), TSInfo(),
 
       // Subtarget features
       m_hasSRAM(false), m_hasJMPCALL(false), m_hasIJMPCALL(false),
@@ -44,4 +44,12 @@ AVRSubtarget::AVRSubtarget(const Triple &TT, const std::string &CPU,
   ParseSubtargetFeatures(CPU, FS);
 }
 
+AVRSubtarget &
+AVRSubtarget::initializeSubtargetDependencies(StringRef CPU, StringRef FS,
+                                              const TargetMachine &TM) {
+  // Parse features string.
+  ParseSubtargetFeatures(CPU, FS);
+  return *this;
+}
+
 } // end of namespace llvm

diff --git a/lib/Target/AVR/AVRSubtarget.h b/lib/Target/AVR/AVRSubtarget.h
index fa26738da1900e1b5e1427b9c7b89551572a96a9..ba036d5e40616c453876b787763deecf81214983 100644 (file)
--- a/lib/Target/AVR/AVRSubtarget.h
+++ b/lib/Target/AVR/AVRSubtarget.h
@@ -37,7 +37,7 @@ public:
   //! \param FS  The feature string.
   //! \param TM  The target machine.
   AVRSubtarget(const Triple &TT, const std::string &CPU, const std::string &FS,
-               AVRTargetMachine &TM);
+               const AVRTargetMachine &TM);
 
   const AVRInstrInfo *getInstrInfo() const override { return &InstrInfo; }
   const TargetFrameLowering *getFrameLowering() const override { return &FrameLowering; }
@@ -49,6 +49,9 @@ public:
   /// \note Definition of function is auto generated by `tblgen`.
   void ParseSubtargetFeatures(StringRef CPU, StringRef FS);
 
+  AVRSubtarget &initializeSubtargetDependencies(StringRef CPU, StringRef FS,
+                                                const TargetMachine &TM);
+
   // Subtarget feature getters.
   // See AVR.td for details.
   bool hasSRAM() const { return m_hasSRAM; }

diff --git a/test/CodeGen/AVR/mul.ll b/test/CodeGen/AVR/hardware-mul.ll
similarity index 90%
rename from test/CodeGen/AVR/mul.ll
rename to test/CodeGen/AVR/hardware-mul.ll
index 2f169347c46e0fdf0a282368d7e40305b5769e72..650697857b76b151ac8bb29c4ba556cd11d98d23 100644 (file)
--- a/test/CodeGen/AVR/mul.ll
+++ b/test/CodeGen/AVR/hardware-mul.ll
@@ -1,5 +1,7 @@
 ; RUN: llc -mattr=mul,movw < %s -march=avr | FileCheck %s
 
+; Tests lowering of multiplication to hardware instructions.
+
 define i8 @mult8(i8 %a, i8 %b) {
 ; CHECK-LABEL: mult8:
 ; CHECK: muls r22, r24

diff --git a/test/CodeGen/AVR/smul-with-overflow.ll b/test/CodeGen/AVR/smul-with-overflow.ll
index 745e93005cc2f22400f94409393ad1311addf28c..9eb2c7411dee85b93b7fe6355ae5630058b72301 100644 (file)
--- a/test/CodeGen/AVR/smul-with-overflow.ll
+++ b/test/CodeGen/AVR/smul-with-overflow.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=avr | FileCheck %s
+; RUN: llc -mattr=avr6 < %s -march=avr | FileCheck %s
 
 define i1 @signed_multiplication_did_overflow(i8, i8) unnamed_addr {
 ; CHECK-LABEL: signed_multiplication_did_overflow:

diff --git a/test/CodeGen/AVR/software-mul.ll b/test/CodeGen/AVR/software-mul.ll
new file mode 100644 (file)
index 0000000..9a4d281
--- /dev/null
+++ b/test/CodeGen/AVR/software-mul.ll
@@ -0,0 +1,28 @@
+; RUN: llc -mattr=avr6,-mul < %s -march=avr | FileCheck %s
+; RUN: llc -mcpu=attiny85 < %s -march=avr | FileCheck %s
+; RUN: llc -mcpu=ata5272 < %s -march=avr | FileCheck %s
+; RUN: llc -mcpu=attiny861a < %s -march=avr | FileCheck %s
+; RUN: llc -mcpu=at90usb82 < %s -march=avr | FileCheck %s
+
+; Tests lowering of multiplication to compiler support routines.
+
+; CHECK-LABEL: mul8:
+define i8 @mul8(i8 %a, i8 %b) {
+; CHECK: mov  r25, r24
+; CHECK: mov  r24, r22
+; CHECK: mov  r22, r25
+; CHECK: call __mulqi3
+  %mul = mul i8 %b, %a
+  ret i8 %mul
+}
+
+; CHECK-LABEL: mul16:
+define i16 @mul16(i16 %a, i16 %b) {
+; CHECK: movw  r18, r24
+; CHECK: movw  r24, r22
+; CHECK: movw  r22, r18
+; CHECK: call  __mulhi3
+  %mul = mul nsw i16 %b, %a
+  ret i16 %mul
+}
+

diff --git a/test/CodeGen/AVR/umul-with-overflow.ll b/test/CodeGen/AVR/umul-with-overflow.ll
index aa8b10a313d380e063fb5e161d03ff023bb18bee..c6457552dea88f90d28aa92474b2869f4b4ad1c4 100644 (file)
--- a/test/CodeGen/AVR/umul-with-overflow.ll
+++ b/test/CodeGen/AVR/umul-with-overflow.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=avr | FileCheck %s
+; RUN: llc -mattr=avr6 < %s -march=avr | FileCheck %s
 
 define i1 @unsigned_multiplication_did_overflow(i8, i8) unnamed_addr {
 ; CHECK-LABEL: unsigned_multiplication_did_overflow: