diff options
| -rw-r--r-- | lib/Analysis/InstructionSimplify.cpp | 16 | ||||
| -rw-r--r-- | test/Transforms/InstSimplify/2010-12-20-Reassociate.ll | 8 |
2 files changed, 23 insertions, 1 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index d5cf626e60..1d4ff0fc9e 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -593,11 +593,25 @@ static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, match(Op0, m_Add(m_Specific(Op1), m_Value(X)))) return X; - /// i1 sub -> xor. + // i1 sub -> xor. if (MaxRecurse && Op0->getType()->isIntegerTy(1)) if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1)) return V; + // X - (X - Y) -> Y. More generally Z - (X - Y) -> (Z - X) + Y if everything + // simplifies. + Value *Y = 0, *Z = Op0; + if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y) + // See if "V === Z - X" simplifies. + if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, DT, MaxRecurse-1)) + // It does! Now see if "W === V + Y" simplifies. + if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, DT, + MaxRecurse-1)) { + // It does, we successfully reassociated! + ++NumReassoc; + return W; + } + // Mul distributes over Sub. Try some generic simplifications based on this. if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul, TD, DT, MaxRecurse)) diff --git a/test/Transforms/InstSimplify/2010-12-20-Reassociate.ll b/test/Transforms/InstSimplify/2010-12-20-Reassociate.ll index 87dfdda910..03d5c33f87 100644 --- a/test/Transforms/InstSimplify/2010-12-20-Reassociate.ll +++ b/test/Transforms/InstSimplify/2010-12-20-Reassociate.ll @@ -62,3 +62,11 @@ define i32 @xor2(i32 %x, i32 %y) { ret i32 %l ; CHECK: ret i32 %y } + +define i32 @sub1(i32 %x, i32 %y) { +; CHECK: @sub1 + %d = sub i32 %x, %y + %r = sub i32 %x, %d + ret i32 %r +; CHECK: ret i32 %y +} |