enhance vmcore to know that udiv's can be exact, and add a trivial

instcombine xform to exercise this.

Nothing forms exact udivs yet though.  This is progress on PR8862



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124992 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 26 insertions, 17 deletions

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 8ef4634..6d71c9e 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -2304,7 +2304,7 @@ bool LLParser::ParseValID(ValID &ID, PerFunctionState *PFS) {
         if (EatIfPresent(lltok::kw_nuw))
           NUW = true;
       }
-    } else if (Opc == Instruction::SDiv) {
+    } else if (Opc == Instruction::SDiv || Opc == Instruction::UDiv) {
       if (EatIfPresent(lltok::kw_exact))
         Exact = true;
     }
@@ -2347,7 +2347,7 @@ bool LLParser::ParseValID(ValID &ID, PerFunctionState *PFS) {
     unsigned Flags = 0;
     if (NUW)   Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
     if (NSW)   Flags |= OverflowingBinaryOperator::NoSignedWrap;
-    if (Exact) Flags |= SDivOperator::IsExact;
+    if (Exact) Flags |= PossiblyExactOperator::IsExact;
     Constant *C = ConstantExpr::get(Opc, Val0, Val1, Flags);
     ID.ConstantVal = C;
     ID.Kind = ValID::t_Constant;
@@ -3032,7 +3032,8 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
   case lltok::kw_fsub:
   case lltok::kw_fmul:    return ParseArithmetic(Inst, PFS, KeywordVal, 2);
 
-  case lltok::kw_sdiv: {
+  case lltok::kw_sdiv:
+  case lltok::kw_udiv: {
     bool Exact = false;
     if (EatIfPresent(lltok::kw_exact))
       Exact = true;
@@ -3043,7 +3044,6 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
     return Result;
   }
 
-  case lltok::kw_udiv:
   case lltok::kw_urem:
   case lltok::kw_srem:   return ParseArithmetic(Inst, PFS, KeywordVal, 1);
   case lltok::kw_fdiv:
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index adcad74..a744d83 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1090,8 +1090,9 @@ bool BitcodeReader::ParseConstants() {
               Flags |= OverflowingBinaryOperator::NoSignedWrap;
             if (Record[3] & (1 << bitc::OBO_NO_UNSIGNED_WRAP))
               Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
-          } else if (Opc == Instruction::SDiv) {
-            if (Record[3] & (1 << bitc::SDIV_EXACT))
+          } else if (Opc == Instruction::SDiv ||
+                     Opc == Instruction::UDiv) {
+            if (Record[3] & (1 << bitc::PEO_EXACT))
               Flags |= SDivOperator::IsExact;
           }
         }
@@ -1905,8 +1906,9 @@ bool BitcodeReader::ParseFunctionBody(Function *F) {
             cast<BinaryOperator>(I)->setHasNoSignedWrap(true);
           if (Record[OpNum] & (1 << bitc::OBO_NO_UNSIGNED_WRAP))
             cast<BinaryOperator>(I)->setHasNoUnsignedWrap(true);
-        } else if (Opc == Instruction::SDiv) {
-          if (Record[OpNum] & (1 << bitc::SDIV_EXACT))
+        } else if (Opc == Instruction::SDiv ||
+                   Opc == Instruction::UDiv) {
+          if (Record[OpNum] & (1 << bitc::PEO_EXACT))
             cast<BinaryOperator>(I)->setIsExact(true);
         }
       }
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index 702a611..f8ef8c6 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -470,9 +470,10 @@ static uint64_t GetOptimizationFlags(const Value *V) {
       Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
     if (OBO->hasNoUnsignedWrap())
       Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
-  } else if (const SDivOperator *Div = dyn_cast<SDivOperator>(V)) {
-    if (Div->isExact())
-      Flags |= 1 << bitc::SDIV_EXACT;
+  } else if (const PossiblyExactOperator *PEO =
+               dyn_cast<PossiblyExactOperator>(V)) {
+    if (PEO->isExact())
+      Flags |= 1 << bitc::PEO_EXACT;
   }
 
   return Flags;
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 035ee72..559788b 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -135,8 +135,8 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
          BO->getOpcode() == Instruction::SDiv)) {
       Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
 
-      // If the division is exact, X % Y is zero.
-      if (SDivOperator *SDiv = dyn_cast<SDivOperator>(BO))
+      // If the division is exact, X % Y is zero, so we end up with X or -X.
+      if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
         if (SDiv->isExact()) {
           if (Op1BO == Op1C)
             return ReplaceInstUsesWith(I, Op0BO);
diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 1a11d9c..5b56cb5 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -831,7 +831,8 @@ static void WriteOptimizationInfo(raw_ostream &Out, const User *U) {
       Out << " nuw";
     if (OBO->hasNoSignedWrap())
       Out << " nsw";
-  } else if (const SDivOperator *Div = dyn_cast<SDivOperator>(U)) {
+  } else if (const PossiblyExactOperator *Div =
+               dyn_cast<PossiblyExactOperator>(U)) {
     if (Div->isExact())
       Out << " exact";
   } else if (const GEPOperator *GEP = dyn_cast<GEPOperator>(U)) {
diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp
index 62117b2..d2359e5 100644
--- a/lib/VMCore/Constants.cpp
+++ b/lib/VMCore/Constants.cpp
@@ -683,7 +683,12 @@ Constant* ConstantExpr::getNUWMul(Constant* C1, Constant* C2) {
 
 Constant* ConstantExpr::getExactSDiv(Constant* C1, Constant* C2) {
   return getTy(C1->getType(), Instruction::SDiv, C1, C2,
-               SDivOperator::IsExact);
+               PossiblyExactOperator::IsExact);
+}
+
+Constant* ConstantExpr::getExactUDiv(Constant* C1, Constant* C2) {
+  return getTy(C1->getType(), Instruction::UDiv, C1, C2,
+               PossiblyExactOperator::IsExact);
 }
 
 // Utility function for determining if a ConstantExpr is a CastOp or not. This
diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 6b561f3..d129028 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -1822,7 +1822,7 @@ void BinaryOperator::setHasNoSignedWrap(bool b) {
 }
 
 void BinaryOperator::setIsExact(bool b) {
-  cast<SDivOperator>(this)->setIsExact(b);
+  cast<PossiblyExactOperator>(this)->setIsExact(b);
 }
 
 bool BinaryOperator::hasNoUnsignedWrap() const {
@@ -1834,7 +1834,7 @@ bool BinaryOperator::hasNoSignedWrap() const {
 }
 
 bool BinaryOperator::isExact() const {
-  return cast<SDivOperator>(this)->isExact();
+  return cast<PossiblyExactOperator>(this)->isExact();
 }
 
 //===----------------------------------------------------------------------===//