Revert "[ARM] Lower UDIV+UREM to UDIV+MLS (and the same for SREM)"

This reverts commit r280808.

It is possible that this change results in an infinite loop. This
is causing timeouts in some tests on ARM, and a Chromebook bot is
failing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280918 91177308-0d34-0410-b5e6-96231b3b80d8

Author: pbarrio

lib/Target/ARM/ARMISelLowering.cpp

@@ -12098,24 +12098,6 @@ SDValue ARMTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
   bool isSigned = (Opcode == ISD::SDIVREM);
   EVT VT = Op->getValueType(0);
   Type *Ty = VT.getTypeForEVT(*DAG.getContext());
-  SDLoc dl(Op);
-
-  // If the target has hardware divide, use divide + multiply + subtract:
-  //     div = a / b
-  //     rem = a - b * div
-  //     return {div, rem}
-  // This should be lowered into UDIV/SDIV + MLS later on.
-  if (Subtarget->hasDivide()) {
-    unsigned DivOpcode = isSigned ? ISD::SDIV : ISD::UDIV;
-    const SDValue Dividend = Op->getOperand(0);
-    const SDValue Divisor = Op->getOperand(1);
-    SDValue Div = DAG.getNode(DivOpcode, dl, VT, Dividend, Divisor);
-    SDValue Mul = DAG.getNode(ISD::MUL, dl, VT, Div, Divisor);
-    SDValue Rem = DAG.getNode(ISD::SUB, dl, VT, Dividend, Mul);
-
-    SDValue Values[2] = {Div, Rem};
-    return DAG.getNode(ISD::MERGE_VALUES, dl, DAG.getVTList(VT, VT), Values);
-  }
 
   RTLIB::Libcall LC = getDivRemLibcall(Op.getNode(),
                                        VT.getSimpleVT().SimpleTy);
@@ -12129,6 +12111,7 @@ SDValue ARMTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
 
   Type *RetTy = (Type*)StructType::get(Ty, Ty, nullptr);
 
+  SDLoc dl(Op);
   TargetLowering::CallLoweringInfo CLI(DAG);
   CLI.setDebugLoc(dl).setChain(InChain)
     .setCallee(getLibcallCallingConv(LC), RetTy, Callee, std::move(Args))

test/CodeGen/ARM/urem-opt-size.ll

@@ -3,12 +3,7 @@
 ; expanded to a sequence of umull, lsrs, muls and sub instructions, but
 ; just a call to __aeabi_uidivmod.
 ;
-; When the processor features hardware division, UDIV + UREM can be turned
-; into UDIV + MLS. This prevents the library function __aeabi_uidivmod to be
-; pulled into the binary. The test uses ARMv7-M.
-;
 ; RUN: llc -mtriple=armv7a-eabi -mattr=-neon -verify-machineinstrs %s -o - | FileCheck %s
-; RUN: llc -mtriple=thumbv7m-eabi -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=V7M
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "thumbv7m-arm-none-eabi"
@@ -33,56 +28,18 @@ entry:
   ret i32 %div
 }
 
-; Test for unsigned remainder
 define i32 @foo3() local_unnamed_addr #0 {
 entry:
 ; CHECK-LABEL: foo3:
 ; CHECK: __aeabi_uidivmod
 ; CHECK-NOT: umull
-; V7M-LABEL: foo3:
-; V7M: udiv [[R2:r[0-9]+]], [[R0:r[0-9]+]], [[R1:r[0-9]+]]
-; V7M: mls {{r[0-9]+}}, [[R2]], [[R1]], [[R0]]
-; V7M-NOT: __aeabi_uidivmod
   %call = tail call i32 bitcast (i32 (...)* @GetValue to i32 ()*)()
   %rem = urem i32 %call, 1000000
   %cmp = icmp eq i32 %rem, 0
   %conv = zext i1 %cmp to i32
   ret i32 %conv
 }
 
-; Test for signed remainder
-define i32 @foo4() local_unnamed_addr #0 {
-entry:
-; CHECK-LABEL: foo4:
-; CHECK:__aeabi_idivmod
-; V7M-LABEL: foo4:
-; V7M: sdiv [[R2:r[0-9]+]], [[R0:r[0-9]+]], [[R1:r[0-9]+]]
-; V7M: mls {{r[0-9]+}}, [[R2]], [[R1]], [[R0]]
-; V7M-NOT: __aeabi_idivmod
-  %call = tail call i32 bitcast (i32 (...)* @GetValue to i32 ()*)()
-  %rem = srem i32 %call, 1000000
-  ret i32 %rem
-}
-
-; Check that doing a sdiv+srem has the same effect as only the srem,
-; as the division needs to be computed anyway in order to calculate
-; the remainder (i.e. make sure we don't end up with two divisions).
-define i32 @foo5() local_unnamed_addr #0 {
-entry:
-; CHECK-LABEL: foo5:
-; CHECK:__aeabi_idivmod
-; V7M-LABEL: foo5:
-; V7M: sdiv [[R2:r[0-9]+]], [[R0:r[0-9]+]], [[R1:r[0-9]+]]
-; V7M-NOT: sdiv
-; V7M: mls {{r[0-9]+}}, [[R2]], [[R1]], [[R0]]
-; V7M-NOT: __aeabi_idivmod
-  %call = tail call i32 bitcast (i32 (...)* @GetValue to i32 ()*)()
-  %div = sdiv i32 %call, 1000000
-  %rem = srem i32 %call, 1000000
-  %add = add i32 %div, %rem
-  ret i32 %add
-}
-
 declare i32 @GetValue(...) local_unnamed_addr
 
 attributes #0 = { minsize nounwind optsize }