lib/Transforms/Utils/IntegerDivision.cpp

   1 //===-- IntegerDivision.cpp - Expand integer division ---------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains an implementation of 32bit and 64bit scalar integer
  10 // division for targets that don't have native support. It's largely derived
  11 // from compiler-rt's implementations of __udivsi3 and __udivmoddi4,
  12 // but hand-tuned for targets that prefer less control flow.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/Transforms/Utils/IntegerDivision.h"
  17 #include "llvm/IR/Function.h"
  18 #include "llvm/IR/IRBuilder.h"
  19 #include "llvm/IR/Instructions.h"
  20 #include "llvm/IR/Intrinsics.h"
  21 #include <utility>
  22
  23 using namespace llvm;
  24
  25 #define DEBUG_TYPE "integer-division"
  26
  27 /// Generate code to compute the remainder of two signed integers. Returns the
  28 /// remainder, which will have the sign of the dividend. Builder's insert point
  29 /// should be pointing where the caller wants code generated, e.g. at the srem
  30 /// instruction. This will generate a urem in the process, and Builder's insert
  31 /// point will be pointing at the uren (if present, i.e. not folded), ready to
  32 /// be expanded if the user wishes
  33 static Value *generateSignedRemainderCode(Value *Dividend, Value *Divisor,
  34                                           IRBuilder<> &Builder) {
  35   unsigned BitWidth = Dividend->getType()->getIntegerBitWidth();
  36   ConstantInt *Shift;
  37
  38   if (BitWidth == 64) {
  39     Shift = Builder.getInt64(63);
  40   } else {
  41     assert(BitWidth == 32 && "Unexpected bit width");
  42     Shift = Builder.getInt32(31);
  43   }
  44
  45   // Following instructions are generated for both i32 (shift 31) and
  46   // i64 (shift 63).
  47
  48   // ;   %dividend_sgn = ashr i32 %dividend, 31
  49   // ;   %divisor_sgn  = ashr i32 %divisor, 31
  50   // ;   %dvd_xor      = xor i32 %dividend, %dividend_sgn
  51   // ;   %dvs_xor      = xor i32 %divisor, %divisor_sgn
  52   // ;   %u_dividend   = sub i32 %dvd_xor, %dividend_sgn
  53   // ;   %u_divisor    = sub i32 %dvs_xor, %divisor_sgn
  54   // ;   %urem         = urem i32 %dividend, %divisor
  55   // ;   %xored        = xor i32 %urem, %dividend_sgn
  56   // ;   %srem         = sub i32 %xored, %dividend_sgn
  57   Value *DividendSign = Builder.CreateAShr(Dividend, Shift);
  58   Value *DivisorSign  = Builder.CreateAShr(Divisor, Shift);
  59   Value *DvdXor       = Builder.CreateXor(Dividend, DividendSign);
  60   Value *DvsXor       = Builder.CreateXor(Divisor, DivisorSign);
  61   Value *UDividend    = Builder.CreateSub(DvdXor, DividendSign);
  62   Value *UDivisor     = Builder.CreateSub(DvsXor, DivisorSign);
  63   Value *URem         = Builder.CreateURem(UDividend, UDivisor);
  64   Value *Xored        = Builder.CreateXor(URem, DividendSign);
  65   Value *SRem         = Builder.CreateSub(Xored, DividendSign);
  66
  67   if (Instruction *URemInst = dyn_cast<Instruction>(URem))
  68     Builder.SetInsertPoint(URemInst);
  69
  70   return SRem;
  71 }
  72
  73
  74 /// Generate code to compute the remainder of two unsigned integers. Returns the
  75 /// remainder. Builder's insert point should be pointing where the caller wants
  76 /// code generated, e.g. at the urem instruction. This will generate a udiv in
  77 /// the process, and Builder's insert point will be pointing at the udiv (if
  78 /// present, i.e. not folded), ready to be expanded if the user wishes
  79 static Value *generatedUnsignedRemainderCode(Value *Dividend, Value *Divisor,
  80                                              IRBuilder<> &Builder) {
  81   // Remainder = Dividend - Quotient*Divisor
  82
  83   // Following instructions are generated for both i32 and i64
  84
  85   // ;   %quotient  = udiv i32 %dividend, %divisor
  86   // ;   %product   = mul i32 %divisor, %quotient
  87   // ;   %remainder = sub i32 %dividend, %product
  88   Value *Quotient  = Builder.CreateUDiv(Dividend, Divisor);
  89   Value *Product   = Builder.CreateMul(Divisor, Quotient);
  90   Value *Remainder = Builder.CreateSub(Dividend, Product);
  91
  92   if (Instruction *UDiv = dyn_cast<Instruction>(Quotient))
  93     Builder.SetInsertPoint(UDiv);
  94
  95   return Remainder;
  96 }
  97
  98 /// Generate code to divide two signed integers. Returns the quotient, rounded
  99 /// towards 0. Builder's insert point should be pointing where the caller wants
 100 /// code generated, e.g. at the sdiv instruction. This will generate a udiv in
 101 /// the process, and Builder's insert point will be pointing at the udiv (if
 102 /// present, i.e. not folded), ready to be expanded if the user wishes.
 103 static Value *generateSignedDivisionCode(Value *Dividend, Value *Divisor,
 104                                          IRBuilder<> &Builder) {
 105   // Implementation taken from compiler-rt's __divsi3 and __divdi3
 106
 107   unsigned BitWidth = Dividend->getType()->getIntegerBitWidth();
 108   ConstantInt *Shift;
 109
 110   if (BitWidth == 64) {
 111     Shift = Builder.getInt64(63);
 112   } else {
 113     assert(BitWidth == 32 && "Unexpected bit width");
 114     Shift = Builder.getInt32(31);
 115   }
 116
 117   // Following instructions are generated for both i32 (shift 31) and
 118   // i64 (shift 63).
 119
 120   // ;   %tmp    = ashr i32 %dividend, 31
 121   // ;   %tmp1   = ashr i32 %divisor, 31
 122   // ;   %tmp2   = xor i32 %tmp, %dividend
 123   // ;   %u_dvnd = sub nsw i32 %tmp2, %tmp
 124   // ;   %tmp3   = xor i32 %tmp1, %divisor
 125   // ;   %u_dvsr = sub nsw i32 %tmp3, %tmp1
 126   // ;   %q_sgn  = xor i32 %tmp1, %tmp
 127   // ;   %q_mag  = udiv i32 %u_dvnd, %u_dvsr
 128   // ;   %tmp4   = xor i32 %q_mag, %q_sgn
 129   // ;   %q      = sub i32 %tmp4, %q_sgn
 130   Value *Tmp    = Builder.CreateAShr(Dividend, Shift);
 131   Value *Tmp1   = Builder.CreateAShr(Divisor, Shift);
 132   Value *Tmp2   = Builder.CreateXor(Tmp, Dividend);
 133   Value *U_Dvnd = Builder.CreateSub(Tmp2, Tmp);
 134   Value *Tmp3   = Builder.CreateXor(Tmp1, Divisor);
 135   Value *U_Dvsr = Builder.CreateSub(Tmp3, Tmp1);
 136   Value *Q_Sgn  = Builder.CreateXor(Tmp1, Tmp);
 137   Value *Q_Mag  = Builder.CreateUDiv(U_Dvnd, U_Dvsr);
 138   Value *Tmp4   = Builder.CreateXor(Q_Mag, Q_Sgn);
 139   Value *Q      = Builder.CreateSub(Tmp4, Q_Sgn);
 140
 141   if (Instruction *UDiv = dyn_cast<Instruction>(Q_Mag))
 142     Builder.SetInsertPoint(UDiv);
 143
 144   return Q;
 145 }
 146
 147 /// Generates code to divide two unsigned scalar 32-bit or 64-bit integers.
 148 /// Returns the quotient, rounded towards 0. Builder's insert point should
 149 /// point where the caller wants code generated, e.g. at the udiv instruction.
 150 static Value *generateUnsignedDivisionCode(Value *Dividend, Value *Divisor,
 151                                            IRBuilder<> &Builder) {
 152   // The basic algorithm can be found in the compiler-rt project's
 153   // implementation of __udivsi3.c. Here, we do a lower-level IR based approach
 154   // that's been hand-tuned to lessen the amount of control flow involved.
 155
 156   // Some helper values
 157   IntegerType *DivTy = cast<IntegerType>(Dividend->getType());
 158   unsigned BitWidth = DivTy->getBitWidth();
 159
 160   ConstantInt *Zero;
 161   ConstantInt *One;
 162   ConstantInt *NegOne;
 163   ConstantInt *MSB;
 164
 165   if (BitWidth == 64) {
 166     Zero      = Builder.getInt64(0);
 167     One       = Builder.getInt64(1);
 168     NegOne    = ConstantInt::getSigned(DivTy, -1);
 169     MSB       = Builder.getInt64(63);
 170   } else {
 171     assert(BitWidth == 32 && "Unexpected bit width");
 172     Zero      = Builder.getInt32(0);
 173     One       = Builder.getInt32(1);
 174     NegOne    = ConstantInt::getSigned(DivTy, -1);
 175     MSB       = Builder.getInt32(31);
 176   }
 177
 178   ConstantInt *True = Builder.getTrue();
 179
 180   BasicBlock *IBB = Builder.GetInsertBlock();
 181   Function *F = IBB->getParent();
 182   Function *CTLZ = Intrinsic::getDeclaration(F->getParent(), Intrinsic::ctlz,
 183                                              DivTy);
 184
 185   // Our CFG is going to look like:
 186   // +---------------------+
 187   // | special-cases       |
 188   // |   ...               |
 189   // +---------------------+
 190   //  |       |
 191   //  |   +----------+
 192   //  |   |  bb1     |
 193   //  |   |  ...     |
 194   //  |   +----------+
 195   //  |    |      |
 196   //  |    |  +------------+
 197   //  |    |  |  preheader |
 198   //  |    |  |  ...       |
 199   //  |    |  +------------+
 200   //  |    |      |
 201   //  |    |      |      +---+
 202   //  |    |      |      |   |
 203   //  |    |  +------------+ |
 204   //  |    |  |  do-while  | |
 205   //  |    |  |  ...       | |
 206   //  |    |  +------------+ |
 207   //  |    |      |      |   |
 208   //  |   +-----------+  +---+
 209   //  |   | loop-exit |
 210   //  |   |  ...      |
 211   //  |   +-----------+
 212   //  |     |
 213   // +-------+
 214   // | ...   |
 215   // | end   |
 216   // +-------+
 217   BasicBlock *SpecialCases = Builder.GetInsertBlock();
 218   SpecialCases->setName(Twine(SpecialCases->getName(), "_udiv-special-cases"));
 219   BasicBlock *End = SpecialCases->splitBasicBlock(Builder.GetInsertPoint(),
 220                                                   "udiv-end");
 221   BasicBlock *LoopExit  = BasicBlock::Create(Builder.getContext(),
 222                                              "udiv-loop-exit", F, End);
 223   BasicBlock *DoWhile   = BasicBlock::Create(Builder.getContext(),
 224                                              "udiv-do-while", F, End);
 225   BasicBlock *Preheader = BasicBlock::Create(Builder.getContext(),
 226                                              "udiv-preheader", F, End);
 227   BasicBlock *BB1       = BasicBlock::Create(Builder.getContext(),
 228                                              "udiv-bb1", F, End);
 229
 230   // We'll be overwriting the terminator to insert our extra blocks
 231   SpecialCases->getTerminator()->eraseFromParent();
 232
 233   // Same instructions are generated for both i32 (msb 31) and i64 (msb 63).
 234
 235   // First off, check for special cases: dividend or divisor is zero, divisor
 236   // is greater than dividend, and divisor is 1.
 237   // ; special-cases:
 238   // ;   %ret0_1      = icmp eq i32 %divisor, 0
 239   // ;   %ret0_2      = icmp eq i32 %dividend, 0
 240   // ;   %ret0_3      = or i1 %ret0_1, %ret0_2
 241   // ;   %tmp0        = tail call i32 @llvm.ctlz.i32(i32 %divisor, i1 true)
 242   // ;   %tmp1        = tail call i32 @llvm.ctlz.i32(i32 %dividend, i1 true)
 243   // ;   %sr          = sub nsw i32 %tmp0, %tmp1
 244   // ;   %ret0_4      = icmp ugt i32 %sr, 31
 245   // ;   %ret0        = or i1 %ret0_3, %ret0_4
 246   // ;   %retDividend = icmp eq i32 %sr, 31
 247   // ;   %retVal      = select i1 %ret0, i32 0, i32 %dividend
 248   // ;   %earlyRet    = or i1 %ret0, %retDividend
 249   // ;   br i1 %earlyRet, label %end, label %bb1
 250   Builder.SetInsertPoint(SpecialCases);
 251   Value *Ret0_1      = Builder.CreateICmpEQ(Divisor, Zero);
 252   Value *Ret0_2      = Builder.CreateICmpEQ(Dividend, Zero);
 253   Value *Ret0_3      = Builder.CreateOr(Ret0_1, Ret0_2);
 254   Value *Tmp0 = Builder.CreateCall(CTLZ, {Divisor, True});
 255   Value *Tmp1 = Builder.CreateCall(CTLZ, {Dividend, True});
 256   Value *SR          = Builder.CreateSub(Tmp0, Tmp1);
 257   Value *Ret0_4      = Builder.CreateICmpUGT(SR, MSB);
 258   Value *Ret0        = Builder.CreateOr(Ret0_3, Ret0_4);
 259   Value *RetDividend = Builder.CreateICmpEQ(SR, MSB);
 260   Value *RetVal      = Builder.CreateSelect(Ret0, Zero, Dividend);
 261   Value *EarlyRet    = Builder.CreateOr(Ret0, RetDividend);
 262   Builder.CreateCondBr(EarlyRet, End, BB1);
 263
 264   // ; bb1:                                             ; preds = %special-cases
 265   // ;   %sr_1     = add i32 %sr, 1
 266   // ;   %tmp2     = sub i32 31, %sr
 267   // ;   %q        = shl i32 %dividend, %tmp2
 268   // ;   %skipLoop = icmp eq i32 %sr_1, 0
 269   // ;   br i1 %skipLoop, label %loop-exit, label %preheader
 270   Builder.SetInsertPoint(BB1);
 271   Value *SR_1     = Builder.CreateAdd(SR, One);
 272   Value *Tmp2     = Builder.CreateSub(MSB, SR);
 273   Value *Q        = Builder.CreateShl(Dividend, Tmp2);
 274   Value *SkipLoop = Builder.CreateICmpEQ(SR_1, Zero);
 275   Builder.CreateCondBr(SkipLoop, LoopExit, Preheader);
 276
 277   // ; preheader:                                           ; preds = %bb1
 278   // ;   %tmp3 = lshr i32 %dividend, %sr_1
 279   // ;   %tmp4 = add i32 %divisor, -1
 280   // ;   br label %do-while
 281   Builder.SetInsertPoint(Preheader);
 282   Value *Tmp3 = Builder.CreateLShr(Dividend, SR_1);
 283   Value *Tmp4 = Builder.CreateAdd(Divisor, NegOne);
 284   Builder.CreateBr(DoWhile);
 285
 286   // ; do-while:                                 ; preds = %do-while, %preheader
 287   // ;   %carry_1 = phi i32 [ 0, %preheader ], [ %carry, %do-while ]
 288   // ;   %sr_3    = phi i32 [ %sr_1, %preheader ], [ %sr_2, %do-while ]
 289   // ;   %r_1     = phi i32 [ %tmp3, %preheader ], [ %r, %do-while ]
 290   // ;   %q_2     = phi i32 [ %q, %preheader ], [ %q_1, %do-while ]
 291   // ;   %tmp5  = shl i32 %r_1, 1
 292   // ;   %tmp6  = lshr i32 %q_2, 31
 293   // ;   %tmp7  = or i32 %tmp5, %tmp6
 294   // ;   %tmp8  = shl i32 %q_2, 1
 295   // ;   %q_1   = or i32 %carry_1, %tmp8
 296   // ;   %tmp9  = sub i32 %tmp4, %tmp7
 297   // ;   %tmp10 = ashr i32 %tmp9, 31
 298   // ;   %carry = and i32 %tmp10, 1
 299   // ;   %tmp11 = and i32 %tmp10, %divisor
 300   // ;   %r     = sub i32 %tmp7, %tmp11
 301   // ;   %sr_2  = add i32 %sr_3, -1
 302   // ;   %tmp12 = icmp eq i32 %sr_2, 0
 303   // ;   br i1 %tmp12, label %loop-exit, label %do-while
 304   Builder.SetInsertPoint(DoWhile);
 305   PHINode *Carry_1 = Builder.CreatePHI(DivTy, 2);
 306   PHINode *SR_3    = Builder.CreatePHI(DivTy, 2);
 307   PHINode *R_1     = Builder.CreatePHI(DivTy, 2);
 308   PHINode *Q_2     = Builder.CreatePHI(DivTy, 2);
 309   Value *Tmp5  = Builder.CreateShl(R_1, One);
 310   Value *Tmp6  = Builder.CreateLShr(Q_2, MSB);
 311   Value *Tmp7  = Builder.CreateOr(Tmp5, Tmp6);
 312   Value *Tmp8  = Builder.CreateShl(Q_2, One);
 313   Value *Q_1   = Builder.CreateOr(Carry_1, Tmp8);
 314   Value *Tmp9  = Builder.CreateSub(Tmp4, Tmp7);
 315   Value *Tmp10 = Builder.CreateAShr(Tmp9, MSB);
 316   Value *Carry = Builder.CreateAnd(Tmp10, One);
 317   Value *Tmp11 = Builder.CreateAnd(Tmp10, Divisor);
 318   Value *R     = Builder.CreateSub(Tmp7, Tmp11);
 319   Value *SR_2  = Builder.CreateAdd(SR_3, NegOne);
 320   Value *Tmp12 = Builder.CreateICmpEQ(SR_2, Zero);
 321   Builder.CreateCondBr(Tmp12, LoopExit, DoWhile);
 322
 323   // ; loop-exit:                                      ; preds = %do-while, %bb1
 324   // ;   %carry_2 = phi i32 [ 0, %bb1 ], [ %carry, %do-while ]
 325   // ;   %q_3     = phi i32 [ %q, %bb1 ], [ %q_1, %do-while ]
 326   // ;   %tmp13 = shl i32 %q_3, 1
 327   // ;   %q_4   = or i32 %carry_2, %tmp13
 328   // ;   br label %end
 329   Builder.SetInsertPoint(LoopExit);
 330   PHINode *Carry_2 = Builder.CreatePHI(DivTy, 2);
 331   PHINode *Q_3     = Builder.CreatePHI(DivTy, 2);
 332   Value *Tmp13 = Builder.CreateShl(Q_3, One);
 333   Value *Q_4   = Builder.CreateOr(Carry_2, Tmp13);
 334   Builder.CreateBr(End);
 335
 336   // ; end:                                 ; preds = %loop-exit, %special-cases
 337   // ;   %q_5 = phi i32 [ %q_4, %loop-exit ], [ %retVal, %special-cases ]
 338   // ;   ret i32 %q_5
 339   Builder.SetInsertPoint(End, End->begin());
 340   PHINode *Q_5 = Builder.CreatePHI(DivTy, 2);
 341
 342   // Populate the Phis, since all values have now been created. Our Phis were:
 343   // ;   %carry_1 = phi i32 [ 0, %preheader ], [ %carry, %do-while ]
 344   Carry_1->addIncoming(Zero, Preheader);
 345   Carry_1->addIncoming(Carry, DoWhile);
 346   // ;   %sr_3 = phi i32 [ %sr_1, %preheader ], [ %sr_2, %do-while ]
 347   SR_3->addIncoming(SR_1, Preheader);
 348   SR_3->addIncoming(SR_2, DoWhile);
 349   // ;   %r_1 = phi i32 [ %tmp3, %preheader ], [ %r, %do-while ]
 350   R_1->addIncoming(Tmp3, Preheader);
 351   R_1->addIncoming(R, DoWhile);
 352   // ;   %q_2 = phi i32 [ %q, %preheader ], [ %q_1, %do-while ]
 353   Q_2->addIncoming(Q, Preheader);
 354   Q_2->addIncoming(Q_1, DoWhile);
 355   // ;   %carry_2 = phi i32 [ 0, %bb1 ], [ %carry, %do-while ]
 356   Carry_2->addIncoming(Zero, BB1);
 357   Carry_2->addIncoming(Carry, DoWhile);
 358   // ;   %q_3 = phi i32 [ %q, %bb1 ], [ %q_1, %do-while ]
 359   Q_3->addIncoming(Q, BB1);
 360   Q_3->addIncoming(Q_1, DoWhile);
 361   // ;   %q_5 = phi i32 [ %q_4, %loop-exit ], [ %retVal, %special-cases ]
 362   Q_5->addIncoming(Q_4, LoopExit);
 363   Q_5->addIncoming(RetVal, SpecialCases);
 364
 365   return Q_5;
 366 }
 367
 368 /// Generate code to calculate the remainder of two integers, replacing Rem with
 369 /// the generated code. This currently generates code using the udiv expansion,
 370 /// but future work includes generating more specialized code, e.g. when more
 371 /// information about the operands are known. Implements both 32bit and 64bit
 372 /// scalar division.
 373 ///
 374 /// Replace Rem with generated code.
 375 bool llvm::expandRemainder(BinaryOperator *Rem) {
 376   assert((Rem->getOpcode() == Instruction::SRem ||
 377           Rem->getOpcode() == Instruction::URem) &&
 378          "Trying to expand remainder from a non-remainder function");
 379
 380   IRBuilder<> Builder(Rem);
 381
 382   assert(!Rem->getType()->isVectorTy() && "Div over vectors not supported");
 383   assert((Rem->getType()->getIntegerBitWidth() == 32 ||
 384           Rem->getType()->getIntegerBitWidth() == 64) &&
 385          "Div of bitwidth other than 32 or 64 not supported");
 386
 387   // First prepare the sign if it's a signed remainder
 388   if (Rem->getOpcode() == Instruction::SRem) {
 389     Value *Remainder = generateSignedRemainderCode(Rem->getOperand(0),
 390                                                    Rem->getOperand(1), Builder);
 391
 392     // Check whether this is the insert point while Rem is still valid.
 393     bool IsInsertPoint = Rem->getIterator() == Builder.GetInsertPoint();
 394     Rem->replaceAllUsesWith(Remainder);
 395     Rem->dropAllReferences();
 396     Rem->eraseFromParent();
 397
 398     // If we didn't actually generate an urem instruction, we're done
 399     // This happens for example if the input were constant. In this case the
 400     // Builder insertion point was unchanged
 401     if (IsInsertPoint)
 402       return true;
 403
 404     BinaryOperator *BO = dyn_cast<BinaryOperator>(Builder.GetInsertPoint());
 405     Rem = BO;
 406   }
 407
 408   Value *Remainder = generatedUnsignedRemainderCode(Rem->getOperand(0),
 409                                                     Rem->getOperand(1),
 410                                                     Builder);
 411
 412   Rem->replaceAllUsesWith(Remainder);
 413   Rem->dropAllReferences();
 414   Rem->eraseFromParent();
 415
 416   // Expand the udiv
 417   if (BinaryOperator *UDiv = dyn_cast<BinaryOperator>(Builder.GetInsertPoint())) {
 418     assert(UDiv->getOpcode() == Instruction::UDiv && "Non-udiv in expansion?");
 419     expandDivision(UDiv);
 420   }
 421
 422   return true;
 423 }
 424
 425
 426 /// Generate code to divide two integers, replacing Div with the generated
 427 /// code. This currently generates code similarly to compiler-rt's
 428 /// implementations, but future work includes generating more specialized code
 429 /// when more information about the operands are known. Implements both
 430 /// 32bit and 64bit scalar division.
 431 ///
 432 /// Replace Div with generated code.
 433 bool llvm::expandDivision(BinaryOperator *Div) {
 434   assert((Div->getOpcode() == Instruction::SDiv ||
 435           Div->getOpcode() == Instruction::UDiv) &&
 436          "Trying to expand division from a non-division function");
 437
 438   IRBuilder<> Builder(Div);
 439
 440   assert(!Div->getType()->isVectorTy() && "Div over vectors not supported");
 441   assert((Div->getType()->getIntegerBitWidth() == 32 ||
 442           Div->getType()->getIntegerBitWidth() == 64) &&
 443          "Div of bitwidth other than 32 or 64 not supported");
 444
 445   // First prepare the sign if it's a signed division
 446   if (Div->getOpcode() == Instruction::SDiv) {
 447     // Lower the code to unsigned division, and reset Div to point to the udiv.
 448     Value *Quotient = generateSignedDivisionCode(Div->getOperand(0),
 449                                                  Div->getOperand(1), Builder);
 450
 451     // Check whether this is the insert point while Div is still valid.
 452     bool IsInsertPoint = Div->getIterator() == Builder.GetInsertPoint();
 453     Div->replaceAllUsesWith(Quotient);
 454     Div->dropAllReferences();
 455     Div->eraseFromParent();
 456
 457     // If we didn't actually generate an udiv instruction, we're done
 458     // This happens for example if the input were constant. In this case the
 459     // Builder insertion point was unchanged
 460     if (IsInsertPoint)
 461       return true;
 462
 463     BinaryOperator *BO = dyn_cast<BinaryOperator>(Builder.GetInsertPoint());
 464     Div = BO;
 465   }
 466
 467   // Insert the unsigned division code
 468   Value *Quotient = generateUnsignedDivisionCode(Div->getOperand(0),
 469                                                  Div->getOperand(1),
 470                                                  Builder);
 471   Div->replaceAllUsesWith(Quotient);
 472   Div->dropAllReferences();
 473   Div->eraseFromParent();
 474
 475   return true;
 476 }
 477
 478 /// Generate code to compute the remainder of two integers of bitwidth up to
 479 /// 32 bits. Uses the above routines and extends the inputs/truncates the
 480 /// outputs to operate in 32 bits; that is, these routines are good for targets
 481 /// that have no or very little suppport for smaller than 32 bit integer
 482 /// arithmetic.
 483 ///
 484 /// Replace Rem with emulation code.
 485 bool llvm::expandRemainderUpTo32Bits(BinaryOperator *Rem) {
 486   assert((Rem->getOpcode() == Instruction::SRem ||
 487           Rem->getOpcode() == Instruction::URem) &&
 488           "Trying to expand remainder from a non-remainder function");
 489
 490   Type *RemTy = Rem->getType();
 491   assert(!RemTy->isVectorTy() && "Div over vectors not supported");
 492
 493   unsigned RemTyBitWidth = RemTy->getIntegerBitWidth();
 494
 495   assert(RemTyBitWidth <= 32 &&
 496          "Div of bitwidth greater than 32 not supported");
 497
 498   if (RemTyBitWidth == 32)
 499     return expandRemainder(Rem);
 500
 501   // If bitwidth smaller than 32 extend inputs, extend output and proceed
 502   // with 32 bit division.
 503   IRBuilder<> Builder(Rem);
 504
 505   Value *ExtDividend;
 506   Value *ExtDivisor;
 507   Value *ExtRem;
 508   Value *Trunc;
 509   Type *Int32Ty = Builder.getInt32Ty();
 510
 511   if (Rem->getOpcode() == Instruction::SRem) {
 512     ExtDividend = Builder.CreateSExt(Rem->getOperand(0), Int32Ty);
 513     ExtDivisor = Builder.CreateSExt(Rem->getOperand(1), Int32Ty);
 514     ExtRem = Builder.CreateSRem(ExtDividend, ExtDivisor);
 515   } else {
 516     ExtDividend = Builder.CreateZExt(Rem->getOperand(0), Int32Ty);
 517     ExtDivisor = Builder.CreateZExt(Rem->getOperand(1), Int32Ty);
 518     ExtRem = Builder.CreateURem(ExtDividend, ExtDivisor);
 519   }
 520   Trunc = Builder.CreateTrunc(ExtRem, RemTy);
 521
 522   Rem->replaceAllUsesWith(Trunc);
 523   Rem->dropAllReferences();
 524   Rem->eraseFromParent();
 525
 526   return expandRemainder(cast<BinaryOperator>(ExtRem));
 527 }
 528
 529 /// Generate code to compute the remainder of two integers of bitwidth up to
 530 /// 64 bits. Uses the above routines and extends the inputs/truncates the
 531 /// outputs to operate in 64 bits.
 532 ///
 533 /// Replace Rem with emulation code.
 534 bool llvm::expandRemainderUpTo64Bits(BinaryOperator *Rem) {
 535   assert((Rem->getOpcode() == Instruction::SRem ||
 536           Rem->getOpcode() == Instruction::URem) &&
 537           "Trying to expand remainder from a non-remainder function");
 538
 539   Type *RemTy = Rem->getType();
 540   assert(!RemTy->isVectorTy() && "Div over vectors not supported");
 541
 542   unsigned RemTyBitWidth = RemTy->getIntegerBitWidth();
 543
 544   assert(RemTyBitWidth <= 64 && "Div of bitwidth greater than 64 not supported");
 545
 546   if (RemTyBitWidth == 64)
 547     return expandRemainder(Rem);
 548
 549   // If bitwidth smaller than 64 extend inputs, extend output and proceed
 550   // with 64 bit division.
 551   IRBuilder<> Builder(Rem);
 552
 553   Value *ExtDividend;
 554   Value *ExtDivisor;
 555   Value *ExtRem;
 556   Value *Trunc;
 557   Type *Int64Ty = Builder.getInt64Ty();
 558
 559   if (Rem->getOpcode() == Instruction::SRem) {
 560     ExtDividend = Builder.CreateSExt(Rem->getOperand(0), Int64Ty);
 561     ExtDivisor = Builder.CreateSExt(Rem->getOperand(1), Int64Ty);
 562     ExtRem = Builder.CreateSRem(ExtDividend, ExtDivisor);
 563   } else {
 564     ExtDividend = Builder.CreateZExt(Rem->getOperand(0), Int64Ty);
 565     ExtDivisor = Builder.CreateZExt(Rem->getOperand(1), Int64Ty);
 566     ExtRem = Builder.CreateURem(ExtDividend, ExtDivisor);
 567   }
 568   Trunc = Builder.CreateTrunc(ExtRem, RemTy);
 569
 570   Rem->replaceAllUsesWith(Trunc);
 571   Rem->dropAllReferences();
 572   Rem->eraseFromParent();
 573
 574   return expandRemainder(cast<BinaryOperator>(ExtRem));
 575 }
 576
 577 /// Generate code to divide two integers of bitwidth up to 32 bits. Uses the
 578 /// above routines and extends the inputs/truncates the outputs to operate
 579 /// in 32 bits; that is, these routines are good for targets that have no
 580 /// or very little support for smaller than 32 bit integer arithmetic.
 581 ///
 582 /// Replace Div with emulation code.
 583 bool llvm::expandDivisionUpTo32Bits(BinaryOperator *Div) {
 584   assert((Div->getOpcode() == Instruction::SDiv ||
 585           Div->getOpcode() == Instruction::UDiv) &&
 586           "Trying to expand division from a non-division function");
 587
 588   Type *DivTy = Div->getType();
 589   assert(!DivTy->isVectorTy() && "Div over vectors not supported");
 590
 591   unsigned DivTyBitWidth = DivTy->getIntegerBitWidth();
 592
 593   assert(DivTyBitWidth <= 32 && "Div of bitwidth greater than 32 not supported");
 594
 595   if (DivTyBitWidth == 32)
 596     return expandDivision(Div);
 597
 598   // If bitwidth smaller than 32 extend inputs, extend output and proceed
 599   // with 32 bit division.
 600   IRBuilder<> Builder(Div);
 601
 602   Value *ExtDividend;
 603   Value *ExtDivisor;
 604   Value *ExtDiv;
 605   Value *Trunc;
 606   Type *Int32Ty = Builder.getInt32Ty();
 607
 608   if (Div->getOpcode() == Instruction::SDiv) {
 609     ExtDividend = Builder.CreateSExt(Div->getOperand(0), Int32Ty);
 610     ExtDivisor = Builder.CreateSExt(Div->getOperand(1), Int32Ty);
 611     ExtDiv = Builder.CreateSDiv(ExtDividend, ExtDivisor);
 612   } else {
 613     ExtDividend = Builder.CreateZExt(Div->getOperand(0), Int32Ty);
 614     ExtDivisor = Builder.CreateZExt(Div->getOperand(1), Int32Ty);
 615     ExtDiv = Builder.CreateUDiv(ExtDividend, ExtDivisor);
 616   }
 617   Trunc = Builder.CreateTrunc(ExtDiv, DivTy);
 618
 619   Div->replaceAllUsesWith(Trunc);
 620   Div->dropAllReferences();
 621   Div->eraseFromParent();
 622
 623   return expandDivision(cast<BinaryOperator>(ExtDiv));
 624 }
 625
 626 /// Generate code to divide two integers of bitwidth up to 64 bits. Uses the
 627 /// above routines and extends the inputs/truncates the outputs to operate
 628 /// in 64 bits.
 629 ///
 630 /// Replace Div with emulation code.
 631 bool llvm::expandDivisionUpTo64Bits(BinaryOperator *Div) {
 632   assert((Div->getOpcode() == Instruction::SDiv ||
 633           Div->getOpcode() == Instruction::UDiv) &&
 634           "Trying to expand division from a non-division function");
 635
 636   Type *DivTy = Div->getType();
 637   assert(!DivTy->isVectorTy() && "Div over vectors not supported");
 638
 639   unsigned DivTyBitWidth = DivTy->getIntegerBitWidth();
 640
 641   assert(DivTyBitWidth <= 64 &&
 642          "Div of bitwidth greater than 64 not supported");
 643
 644   if (DivTyBitWidth == 64)
 645     return expandDivision(Div);
 646
 647   // If bitwidth smaller than 64 extend inputs, extend output and proceed
 648   // with 64 bit division.
 649   IRBuilder<> Builder(Div);
 650
 651   Value *ExtDividend;
 652   Value *ExtDivisor;
 653   Value *ExtDiv;
 654   Value *Trunc;
 655   Type *Int64Ty = Builder.getInt64Ty();
 656
 657   if (Div->getOpcode() == Instruction::SDiv) {
 658     ExtDividend = Builder.CreateSExt(Div->getOperand(0), Int64Ty);
 659     ExtDivisor = Builder.CreateSExt(Div->getOperand(1), Int64Ty);
 660     ExtDiv = Builder.CreateSDiv(ExtDividend, ExtDivisor);
 661   } else {
 662     ExtDividend = Builder.CreateZExt(Div->getOperand(0), Int64Ty);
 663     ExtDivisor = Builder.CreateZExt(Div->getOperand(1), Int64Ty);
 664     ExtDiv = Builder.CreateUDiv(ExtDividend, ExtDivisor);
 665   }
 666   Trunc = Builder.CreateTrunc(ExtDiv, DivTy);
 667
 668   Div->replaceAllUsesWith(Trunc);
 669   Div->dropAllReferences();
 670   Div->eraseFromParent();
 671
 672   return expandDivision(cast<BinaryOperator>(ExtDiv));
 673 }