simple fix for an incorrect factoring which causes a

miscompilation, PR5458.

llvm-svn: 92354

lib/Transforms/Scalar/Reassociate.cpp

@@ -714,6 +714,10 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
     // To efficiently find this, we count the number of times a factor occurs
     // for any ADD operands that are MULs.
     DenseMap<Value*, unsigned> FactorOccurrences;
+      
+    // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
+    // where they are actually the same multiply.
+    SmallPtrSet<BinaryOperator*, 4> Multiplies;
     unsigned MaxOcc = 0;
     Value *MaxOccVal = 0;
     for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
@@ -721,6 +725,9 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
       if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
         continue;
       
+      // If we've already seen this multiply, don't revisit it.
+      if (!Multiplies.insert(BOp)) continue;
+      
       // Compute all of the factors of this added value.
       SmallVector<Value*, 8> Factors;
       FindSingleUseMultiplyFactors(BOp, Factors);

test/Transforms/Reassociate/basictest.ll

@@ -133,3 +133,14 @@ define i32 @test8(i32 %X, i32 %Y, i32 %Z) {
 ; CHECK-NEXT: %C = sub i32 %Z, %A
 ; CHECK-NEXT: ret i32 %C
 }
+
+
+; PR5458
+define i32 @test9(i32 %X) {
+  %Y = mul i32 %X, 47
+  %Z = add i32 %Y, %Y
+  ret i32 %Z
+; CHECK: @test9
+; CHECK-NEXT: %Z = mul i32 %X, 94
+; CHECK-NEXT: ret i32 %Z
+}