diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp index 964fe90c467d..991b11110b41 100644 --- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp +++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp @@ -9,23 +9,6 @@ // // This file implements the Jump Threading pass. // -// Jump threading tries to find distinct threads of control flow running through -// a basic block. This pass looks at blocks that have multiple predecessors and -// multiple successors. If one or more of the predecessors of the block can be -// proven to always cause a jump to one of the successors, we forward the edge -// from the predecessor to the successor by duplicating the contents of this -// block. -// -// An example of when this can occur is code like this: -// -// if () { ... -// X = 4; -// } -// if (X < 3) { -// -// In this case, the unconditional branch at the end of the first if can be -// revectored to the false side of the second if. -// //===----------------------------------------------------------------------===// #define DEBUG_TYPE "jump-threading" @@ -50,6 +33,22 @@ Threshold("jump-threading-threshold", cl::init(6), cl::Hidden); namespace { + /// This pass performs 'jump threading', which looks at blocks that have + /// multiple predecessors and multiple successors. If one or more of the + /// predecessors of the block can be proven to always jump to one of the + /// successors, we forward the edge from the predecessor to the successor by + /// duplicating the contents of this block. + /// + /// An example of when this can occur is code like this: + /// + /// if () { ... + /// X = 4; + /// } + /// if (X < 3) { + /// + /// In this case, the unconditional branch at the end of the first if can be + /// revectored to the false side of the second if. + /// class VISIBILITY_HIDDEN JumpThreading : public FunctionPass { public: static char ID; // Pass identification