diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/Reassociate.cpp | 31 | ||||
| -rw-r--r-- | llvm/test/Transforms/Reassociate/basictest.ll | 13 |
2 files changed, 43 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp index d22b9bfc40b..bbb0e0a2dfc 100644 --- a/llvm/lib/Transforms/Scalar/Reassociate.cpp +++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp @@ -376,6 +376,9 @@ void Reassociate::RewriteExprTree(BinaryOperator *I, // that should be processed next by the reassociation pass. // static Value *NegateValue(Value *V, Instruction *BI) { + if (Constant *C = dyn_cast<Constant>(V)) + return ConstantExpr::getNeg(C); + // We are trying to expose opportunity for reassociation. One of the things // that we want to do to achieve this is to push a negation as deep into an // expression chain as possible, to expose the add instructions. In practice, @@ -400,10 +403,36 @@ static Value *NegateValue(Value *V, Instruction *BI) { I->setName(I->getName()+".neg"); return I; } + + // Okay, we need to materialize a negated version of V with an instruction. + // Scan the use lists of V to see if we have one already. + for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ + if (!BinaryOperator::isNeg(*UI)) continue; + + // We found one! Now we have to make sure that the definition dominates + // this use. We do this by moving it to the entry block (if it is a + // non-instruction value) or right after the definition. These negates will + // be zapped by reassociate later, so we don't need much finesse here. + BinaryOperator *TheNeg = cast<BinaryOperator>(*UI); + + BasicBlock::iterator InsertPt; + if (Instruction *InstInput = dyn_cast<Instruction>(V)) { + if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) { + InsertPt = II->getNormalDest()->begin(); + } else { + InsertPt = InstInput; + ++InsertPt; + } + while (isa<PHINode>(InsertPt)) ++InsertPt; + } else { + InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin(); + } + TheNeg->moveBefore(InsertPt); + return TheNeg; + } // Insert a 'neg' instruction that subtracts the value from zero to get the // negation. - // return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI); } diff --git a/llvm/test/Transforms/Reassociate/basictest.ll b/llvm/test/Transforms/Reassociate/basictest.ll index af08b583bb4..0f137dc8add 100644 --- a/llvm/test/Transforms/Reassociate/basictest.ll +++ b/llvm/test/Transforms/Reassociate/basictest.ll @@ -165,4 +165,17 @@ define i32 @test11(i32 %W) { ; CHECK-NEXT: ret i32 } +define i32 @test12(i32 %X) { + %A = sub i32 1, %X + %B = sub i32 2, %X + %C = sub i32 3, %X + + %Y = add i32 %A ,%B + %Z = add i32 %Y, %C + ret i32 %Z +; CHECK: @test12 +; CHECK-NEXT: mul i32 %X, -3 +; CHECK-NEXT: add i32{{.*}}, 6 +; CHECK-NEXT: ret i32 +} |
