diff options
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 23 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/switch-to-icmp.ll | 40 |
2 files changed, 57 insertions, 6 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index bf753dc..93d8143 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2241,14 +2241,25 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { /// integer range comparison into a sub, an icmp and a branch. static bool TurnSwitchRangeIntoICmp(SwitchInst *SI) { assert(SI->getNumCases() > 2 && "Degenerate switch?"); - // We can do this transform if the switch consists of an ascending series - // and all cases point to the same destination. - for (unsigned I = 2, E = SI->getNumCases(); I != E; ++I) - if (SI->getSuccessor(I-1) != SI->getSuccessor(I) || - SI->getCaseValue(I-1)->getValue()+1 != SI->getCaseValue(I)->getValue()) + + // Make sure all cases point to the same destination and gather the values. + SmallVector<ConstantInt *, 16> Cases; + Cases.push_back(SI->getCaseValue(1)); + for (unsigned I = 2, E = SI->getNumCases(); I != E; ++I) { + if (SI->getSuccessor(I-1) != SI->getSuccessor(I)) return false; + Cases.push_back(SI->getCaseValue(I)); + } + assert(Cases.size() == SI->getNumCases()-1 && "Not all cases gathered"); + + // Sort the case values, then check if they form a range we can transform. + array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate); + for (unsigned I = 1, E = Cases.size(); I != E; ++I) { + if (Cases[I-1]->getValue() != Cases[I]->getValue()+1) + return false; + } - Constant *Offset = ConstantExpr::getNeg(SI->getCaseValue(1)); + Constant *Offset = ConstantExpr::getNeg(Cases.back()); Constant *NumCases = ConstantInt::get(Offset->getType(), SI->getNumCases()-1); Value *Sub = BinaryOperator::CreateAdd(SI->getCondition(), Offset, "off", SI); diff --git a/test/Transforms/SimplifyCFG/switch-to-icmp.ll b/test/Transforms/SimplifyCFG/switch-to-icmp.ll new file mode 100644 index 0000000..2499cdb --- /dev/null +++ b/test/Transforms/SimplifyCFG/switch-to-icmp.ll @@ -0,0 +1,40 @@ +; RUN: opt -S -simplifycfg < %s | FileCheck %s + +define zeroext i1 @test1(i32 %x) nounwind readnone ssp noredzone { +entry: + switch i32 %x, label %lor.rhs [ + i32 2, label %lor.end + i32 1, label %lor.end + i32 3, label %lor.end + ] + +lor.rhs: + br label %lor.end + +lor.end: + %0 = phi i1 [ true, %entry ], [ false, %lor.rhs ], [ true, %entry ], [ true, %entry ] + ret i1 %0 + +; CHECK: @test1 +; CHECK: %off = add i32 %x, -1 +; CHECK: %switch = icmp ult i32 %off, 3 +} + +define zeroext i1 @test2(i32 %x) nounwind readnone ssp noredzone { +entry: + switch i32 %x, label %lor.rhs [ + i32 0, label %lor.end + i32 1, label %lor.end + ] + +lor.rhs: + br label %lor.end + +lor.end: + %0 = phi i1 [ true, %entry ], [ false, %lor.rhs ], [ true, %entry ] + ret i1 %0 + +; CHECK: @test2 +; CHECK: %off = add i32 %x, 0 +; CHECK: %switch = icmp ult i32 %off, 2 +} |