1 files changed, 28 insertions, 7 deletions
diff --git a/contrib/llvm/lib/Transforms/Utils/BypassSlowDivision.cpp b/contrib/llvm/lib/Transforms/Utils/BypassSlowDivision.cpp
index 42287d3..bc2cef2 100644
--- a/contrib/llvm/lib/Transforms/Utils/BypassSlowDivision.cpp
+++ b/contrib/llvm/lib/Transforms/Utils/BypassSlowDivision.cpp
@@ -20,6 +20,7 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/Transforms/Utils/Local.h"
 
 using namespace llvm;
 
@@ -82,13 +83,17 @@ static bool insertFastDiv(Instruction *I, IntegerType *BypassType,
   Value *Dividend = I->getOperand(0);
   Value *Divisor = I->getOperand(1);
 
-  if (isa<ConstantInt>(Divisor) ||
-      (isa<ConstantInt>(Dividend) && isa<ConstantInt>(Divisor))) {
-    // Operations with immediate values should have
-    // been solved and replaced during compile time.
+  if (isa<ConstantInt>(Divisor)) {
+    // Division by a constant should have been been solved and replaced earlier
+    // in the pipeline.
     return false;
   }
 
+  // If the numerator is a constant, bail if it doesn't fit into BypassType.
+  if (ConstantInt *ConstDividend = dyn_cast<ConstantInt>(Dividend))
+    if (ConstDividend->getValue().getActiveBits() > BypassType->getBitWidth())
+      return false;
+
   // Basic Block is split before divide
   BasicBlock *MainBB = &*I->getParent();
   BasicBlock *SuccessorBB = MainBB->splitBasicBlock(I);
@@ -120,8 +125,7 @@ static bool insertFastDiv(Instruction *I, IntegerType *BypassType,
                                                  BypassType);
 
   // udiv/urem because optimization only handles positive numbers
-  Value *ShortQuotientV = FastBuilder.CreateExactUDiv(ShortDividendV,
-                                                      ShortDivisorV);
+  Value *ShortQuotientV = FastBuilder.CreateUDiv(ShortDividendV, ShortDivisorV);
   Value *ShortRemainderV = FastBuilder.CreateURem(ShortDividendV,
                                                   ShortDivisorV);
   Value *FastQuotientV = FastBuilder.CreateCast(Instruction::ZExt,
@@ -151,7 +155,17 @@ static bool insertFastDiv(Instruction *I, IntegerType *BypassType,
   // Combine operands into a single value with OR for value testing below
   MainBB->getInstList().back().eraseFromParent();
   IRBuilder<> MainBuilder(MainBB, MainBB->end());
-  Value *OrV = MainBuilder.CreateOr(Dividend, Divisor);
+
+  // We should have bailed out above if the divisor is a constant, but the
+  // dividend may still be a constant.  Set OrV to our non-constant operands
+  // OR'ed together.
+  assert(!isa<ConstantInt>(Divisor));
+
+  Value *OrV;
+  if (!isa<ConstantInt>(Dividend))
+    OrV = MainBuilder.CreateOr(Dividend, Divisor);
+  else
+    OrV = Divisor;
 
   // BitMask is inverted to check if the operands are
   // larger than the bypass type
@@ -247,5 +261,12 @@ bool llvm::bypassSlowDivision(
     MadeChange |= reuseOrInsertFastDiv(I, BT, UseDivOp, UseSignedOp, DivCache);
   }
 
+  // Above we eagerly create divs and rems, as pairs, so that we can efficiently
+  // create divrem machine instructions.  Now erase any unused divs / rems so we
+  // don't leave extra instructions sitting around.
+  for (auto &KV : DivCache)
+    for (Instruction *Phi : {KV.second.Quotient, KV.second.Remainder})
+      RecursivelyDeleteTriviallyDeadInstructions(Phi);
+
   return MadeChange;
 }