[ARM] Lower modulo operation to generate __aeabi_divmod on Android

[sgundapa]

Summary

For a modulo (reminder) operation,
clang -target armv7-none-linux-gnueabi generates "_ _modsi3"
clang -target armv7-none-eabi generates "_ _aeabi_idivmod"
clang -target armv7-linux-androideabi generates "_ _modsi3"

Android bionic libc doesn't provide a _ _modsi3, instead it provides a
"_ _aeabi_idivmod". This patch fixes the LLVM ARMISelLowering to generate
the correct call when ever there is a modulo operation.

[t.p.northover]

This looks reasonable to me.

Tim.

[rengolin]

Sumanth, do you have commit rights?

[asl]

lib/Target/ARM/ARMISelLowering.cpp

742

What are the differences between "EABI" and "androideabi"? Can't we simply assume that "androideabi" is "eabi" ?

[sgundapa]

Renato, I have commit rights.

What are the differences between "EABI" and "androideabi"? Can't we simply assume that "androideabi" is "eabi" ?

It depends and assumption changes over time.

[sgundapa]

This patch was merged

lib/Target/ARM/ARMISelLowering.cpp

ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
 
   if (!(Subtarget->hasDivide() && Subtarget->isThumb2()) &&
       !(Subtarget->hasDivideInARMMode() && !Subtarget->isThumb())) {
     // These are expanded into libcalls if the cpu doesn't have HW divider.
     setOperationAction(ISD::SDIV,  MVT::i32, Expand);
     setOperationAction(ISD::UDIV,  MVT::i32, Expand);
   }
 
-  // FIXME: Also set divmod for SREM on EABI
+  // FIXME: Also set divmod for SREM on EABI/androideabi
   setOperationAction(ISD::SREM,  MVT::i32, Expand);
   setOperationAction(ISD::UREM,  MVT::i32, Expand);
   // Register based DivRem for AEABI (RTABI 4.2)
-  if (Subtarget->isTargetAEABI()) {
+  if (Subtarget->isTargetAEABI() || Subtarget->isTargetAndroid()) {
     setLibcallName(RTLIB::SDIVREM_I8,  "__aeabi_idivmod");
     setLibcallName(RTLIB::SDIVREM_I16, "__aeabi_idivmod");
     setLibcallName(RTLIB::SDIVREM_I32, "__aeabi_idivmod");
     setLibcallName(RTLIB::SDIVREM_I64, "__aeabi_ldivmod");
     setLibcallName(RTLIB::UDIVREM_I8,  "__aeabi_uidivmod");
     setLibcallName(RTLIB::UDIVREM_I16, "__aeabi_uidivmod");
     setLibcallName(RTLIB::UDIVREM_I32, "__aeabi_uidivmod");
     setLibcallName(RTLIB::UDIVREM_I64, "__aeabi_uldivmod");
void ARMTargetLowering::LowerAsmOperandForConstraint(SDValue Op,
   if (Result.getNode()) {
     Ops.push_back(Result);
     return;
   }
   return TargetLowering::LowerAsmOperandForConstraint(Op, Constraint, Ops, DAG);
 }
 
 SDValue ARMTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
-  assert(Subtarget->isTargetAEABI() && "Register-based DivRem lowering only");
+  assert((Subtarget->isTargetAEABI() || Subtarget->isTargetAndroid()) &&
+         "Register-based DivRem lowering only");
   unsigned Opcode = Op->getOpcode();
   assert((Opcode == ISD::SDIVREM || Opcode == ISD::UDIVREM) &&
          "Invalid opcode for Div/Rem lowering");
   bool isSigned = (Opcode == ISD::SDIVREM);
   EVT VT = Op->getValueType(0);
   Type *Ty = VT.getTypeForEVT(*DAG.getContext());
 
   RTLIB::Libcall LC;

test/CodeGen/ARM/divmod-eabi.ll

 ; RUN: llc -mtriple armv7-none-eabi %s -o - | FileCheck %s --check-prefix=EABI
 ; RUN: llc -mtriple armv7-none-eabihf %s -o - | FileCheck %s --check-prefix=EABI
+; Both "none-eabi" and "androideabi" must lower SREM/UREM to __aeabi_{u,i}divmod
+; RUN: llc -mtriple armv7-linux-androideabi %s -o - | FileCheck %s --check-prefix=EABI
 ; RUN: llc -mtriple armv7-linux-gnueabi %s -o - | FileCheck %s --check-prefix=GNU
 ; RUN: llc -mtriple armv7-apple-darwin %s -o - | FileCheck %s --check-prefix=DARWIN
 ; FIXME: long-term, we will use "-apple-macho" and won't need this exception:
 ; RUN: llc -mtriple armv7-apple-darwin-eabi %s -o - | FileCheck %s --check-prefix=DARWIN
 
 define signext i16 @f16(i16 signext %a, i16 signext %b) {
 ; EABI-LABEL: f16:
 ; GNU-LABEL: f16: