[SubZero] Use DIV instruction instead of TargetHelperCall

src/IceTargetLoweringMIPS32.cpp

Index: src/IceTargetLoweringMIPS32.cpp
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index c4b602463f20af75a03df68d14f4f43a92998fa5..b3570a63c5c2a1f78158195e121c09e3d2842afd 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -277,71 +277,6 @@ void TargetMIPS32::genTargetHelperCallFor(Inst *Instr) {
       Instr->setDeleted();
       return;
     }
-    case IceType_i32:
-    case IceType_i16:
-    case IceType_i8: {
-      InstCast::OpKind CastKind;
-      RuntimeHelper HelperID = RuntimeHelper::H_Num;
-      switch (Op) {
-      default:
-        return;
-      case InstArithmetic::Udiv:
-        HelperID = RuntimeHelper::H_udiv_i32;
-        CastKind = InstCast::Zext;
-        break;
-      case InstArithmetic::Sdiv:
-        HelperID = RuntimeHelper::H_sdiv_i32;
-        CastKind = InstCast::Sext;
-        break;
-      case InstArithmetic::Urem:
-        HelperID = RuntimeHelper::H_urem_i32;
-        CastKind = InstCast::Zext;
-        break;
-      case InstArithmetic::Srem:
-        HelperID = RuntimeHelper::H_srem_i32;
-        CastKind = InstCast::Sext;
-        break;
-      }
-
-      if (HelperID == RuntimeHelper::H_Num) {
-        return;
-      }
-
-      Operand *Src0 = Instr->getSrc(0);
-      Operand *Src1 = Instr->getSrc(1);
-      if (DestTy != IceType_i32) {
-        // Src0 and Src1 have to be zero-, or signed-extended to i32. For Src0,
-        // we just insert a InstCast right before the call to the helper.
-        Variable *Src0_32 = Func->makeVariable(IceType_i32);
-        Context.insert<InstCast>(CastKind, Src0_32, Src0);
-        Src0 = Src0_32;
-
-        if (auto *C = llvm::dyn_cast<ConstantInteger32>(Src1)) {
-          const int32_t ShAmt = (DestTy == IceType_i16) ? 16 : 24;
-          int32_t NewC = C->getValue();
-          if (CastKind == InstCast::Zext) {
-            NewC &= ~(0x80000000l >> ShAmt);
-          } else {
-            NewC = (NewC << ShAmt) >> ShAmt;
-          }
-          Src1 = Ctx->getConstantInt32(NewC);
-        } else {
-          Variable *Src1_32 = Func->makeVariable(IceType_i32);
-          Context.insert<InstCast>(CastKind, Src1_32, Src1);
-          Src1 = Src1_32;
-        }
-      }
-      Operand *TargetHelper = Ctx->getRuntimeHelperFunc(HelperID);
-      constexpr SizeT MaxArgs = 2;
-      auto *Call = Context.insert<InstCall>(MaxArgs, Dest, TargetHelper,
-                                            NoTailCall, IsTargetHelperCall);
-      assert(Src0->getType() == IceType_i32);
-      Call->addArg(Src0);
-      assert(Src1->getType() == IceType_i32);
-      Call->addArg(Src1);
-      Instr->setDeleted();
-      return;
-    }
     case IceType_f32:
     case IceType_f64: {
       if (Op != InstArithmetic::Frem) {
@@ -1957,6 +1892,7 @@ void TargetMIPS32::lowerArithmetic(const InstArithmetic *Instr) {
   case InstArithmetic::Udiv: {
     auto *T_Zero = I32Reg(RegMIPS32::Reg_ZERO);
     _divu(T_Zero, Src0R, Src1R);
+    _teq(Src1R, T_Zero, 7); // Trap if divide-by-zero

[Jim Stichnoth, 2016/09/16 16:33:02]

I like to avoid magic constants when possible.

Instead, maybe somewhere before this switch statement:
  constexpr uint32_t TrapIfDivideByZero = 7;

or whatever it should be named to convey the proper semantics (I'm just guessing
here).

[jaydeep.patil, 2016/09/19 03:30:51]

Done.

     _mflo(T, T_Zero);
     _mov(Dest, T);
     return;
@@ -1964,6 +1900,7 @@ void TargetMIPS32::lowerArithmetic(const InstArithmetic *Instr) {
   case InstArithmetic::Sdiv: {
     auto *T_Zero = I32Reg(RegMIPS32::Reg_ZERO);
     _div(T_Zero, Src0R, Src1R);
+    _teq(Src1R, T_Zero, 7); // Trap if divide-by-zero

[obucinac, 2016/09/19 03:37:04]

auto *T_Zero = I32Reg(RegMIPS32::Reg_ZERO);
_teq(Src1R, T_Zero, 7);

May be changed with simpler

_teq(Src1R, getZero(), 7);

[jaydeep.patil, 2016/09/19 05:04:40]

Calling getZero() for each occurrence of T_Zero is not efficient. 

     _mflo(T, T_Zero);
     _mov(Dest, T);
     return;
@@ -1971,6 +1908,7 @@ void TargetMIPS32::lowerArithmetic(const InstArithmetic *Instr) {
   case InstArithmetic::Urem: {
     auto *T_Zero = I32Reg(RegMIPS32::Reg_ZERO);
     _divu(T_Zero, Src0R, Src1R);
+    _teq(Src1R, T_Zero, 7); // Trap if divide-by-zero
     _mfhi(T, T_Zero);
     _mov(Dest, T);
     return;
@@ -1978,6 +1916,7 @@ void TargetMIPS32::lowerArithmetic(const InstArithmetic *Instr) {
   case InstArithmetic::Srem: {
     auto *T_Zero = I32Reg(RegMIPS32::Reg_ZERO);
     _div(T_Zero, Src0R, Src1R);
+    _teq(Src1R, T_Zero, 7); // Trap if divide-by-zero
     _mfhi(T, T_Zero);
     _mov(Dest, T);
     return;