[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.
llvm-svn: 351523
diff --git a/llvm/lib/Target/AVR/AVRISelLowering.cpp b/llvm/lib/Target/AVR/AVRISelLowering.cpp
index 57fc978..5db7577 100644
--- a/llvm/lib/Target/AVR/AVRISelLowering.cpp
+++ b/llvm/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 @@
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 @@
// 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 @@
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 @@
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 @@
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 @@
}
}
- return TargetLowering::getRegForInlineAsmConstraint(STI->getRegisterInfo(),
- Constraint, VT);
+ return TargetLowering::getRegForInlineAsmConstraint(
+ Subtarget.getRegisterInfo(), Constraint, VT);
}
void AVRTargetLowering::LowerAsmOperandForConstraint(SDValue Op,