diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/LoopUnswitch.cpp | 26 | ||||
| -rw-r--r-- | llvm/test/Transforms/LoopUnswitch/exponential-behavior.ll | 51 |
2 files changed, 73 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp index 30aae21c90c..7aa730474d7 100644 --- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp +++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp @@ -389,7 +389,11 @@ Pass *llvm::createLoopUnswitchPass(bool Os) { /// Cond is a condition that occurs in L. If it is invariant in the loop, or has /// an invariant piece, return the invariant. Otherwise, return null. -static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { +static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed, + DenseMap<Value *, Value *> &Cache) { + auto CacheIt = Cache.find(Cond); + if (CacheIt != Cache.end()) + return CacheIt->second; // We started analyze new instruction, increment scanned instructions counter. ++TotalInsts; @@ -404,8 +408,10 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { // TODO: Handle: br (VARIANT|INVARIANT). // Hoist simple values out. - if (L->makeLoopInvariant(Cond, Changed)) + if (L->makeLoopInvariant(Cond, Changed)) { + Cache[Cond] = Cond; return Cond; + } if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond)) if (BO->getOpcode() == Instruction::And || @@ -413,15 +419,27 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { // If either the left or right side is invariant, we can unswitch on this, // which will cause the branch to go away in one loop and the condition to // simplify in the other one. - if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed)) + if (Value *LHS = + FindLIVLoopCondition(BO->getOperand(0), L, Changed, Cache)) { + Cache[Cond] = LHS; return LHS; - if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed)) + } + if (Value *RHS = + FindLIVLoopCondition(BO->getOperand(1), L, Changed, Cache)) { + Cache[Cond] = RHS; return RHS; + } } + Cache[Cond] = nullptr; return nullptr; } +static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { + DenseMap<Value *, Value *> Cache; + return FindLIVLoopCondition(Cond, L, Changed, Cache); +} + bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) { if (skipLoop(L)) return false; diff --git a/llvm/test/Transforms/LoopUnswitch/exponential-behavior.ll b/llvm/test/Transforms/LoopUnswitch/exponential-behavior.ll new file mode 100644 index 00000000000..fb5a1ccf87b --- /dev/null +++ b/llvm/test/Transforms/LoopUnswitch/exponential-behavior.ll @@ -0,0 +1,51 @@ +; RUN: opt -loop-unswitch -S < %s | FileCheck %s + +define void @f(i32 %n, i32* %ptr) { +; CHECK-LABEL: @f( +entry: + br label %loop + +loop: + %iv = phi i32 [ 0, %entry ], [ %iv.inc, %be ] + %iv.inc = add i32 %iv, 1 + %unswitch_cond_root = icmp ne i32 %iv.inc, 42 + %us.0 = and i1 %unswitch_cond_root, %unswitch_cond_root + %us.1 = and i1 %us.0, %us.0 + %us.2 = and i1 %us.1, %us.1 + %us.3 = and i1 %us.2, %us.2 + %us.4 = and i1 %us.3, %us.3 + %us.5 = and i1 %us.4, %us.4 + %us.6 = and i1 %us.5, %us.5 + %us.7 = and i1 %us.6, %us.6 + %us.8 = and i1 %us.7, %us.7 + %us.9 = and i1 %us.8, %us.8 + %us.10 = and i1 %us.9, %us.9 + %us.11 = and i1 %us.10, %us.10 + %us.12 = and i1 %us.11, %us.11 + %us.13 = and i1 %us.12, %us.12 + %us.14 = and i1 %us.13, %us.13 + %us.15 = and i1 %us.14, %us.14 + %us.16 = and i1 %us.15, %us.15 + %us.17 = and i1 %us.16, %us.16 + %us.18 = and i1 %us.17, %us.17 + %us.19 = and i1 %us.18, %us.18 + %us.20 = and i1 %us.19, %us.19 + %us.21 = and i1 %us.20, %us.20 + %us.22 = and i1 %us.21, %us.21 + %us.23 = and i1 %us.22, %us.22 + %us.24 = and i1 %us.23, %us.23 + %us.25 = and i1 %us.24, %us.24 + %us.26 = and i1 %us.25, %us.25 + %us.27 = and i1 %us.26, %us.26 + %us.28 = and i1 %us.27, %us.27 + %us.29 = and i1 %us.28, %us.28 + br i1 %us.29, label %leave, label %be + +be: + store volatile i32 0, i32* %ptr + %becond = icmp ult i32 %iv.inc, %n + br i1 %becond, label %leave, label %loop + +leave: + ret void +} |
