diff options
Diffstat (limited to 'lib/CodeGen/MachineSink.cpp')
| -rw-r--r-- | lib/CodeGen/MachineSink.cpp | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp index 7717fc88cf..d158c481ee 100644 --- a/lib/CodeGen/MachineSink.cpp +++ b/lib/CodeGen/MachineSink.cpp @@ -7,7 +7,12 @@ // //===----------------------------------------------------------------------===// // -// This pass +// This pass moves instructions into successor blocks, when possible, so that +// they aren't executed on paths where their results aren't needed. +// +// This pass is not intended to be a replacement or a complete alternative +// for an LLVM-IR-level sinking pass. It is only designed to sink simple +// constructs that are not exposed before lowering and instruction selection. // //===----------------------------------------------------------------------===// @@ -31,7 +36,7 @@ namespace { const TargetInstrInfo *TII; MachineFunction *CurMF; // Current MachineFunction MachineRegisterInfo *RegInfo; // Machine register information - MachineDominatorTree *DT; // Machine dominator tree for the current Loop + MachineDominatorTree *DT; // Machine dominator tree public: static char ID; // Pass identification @@ -152,7 +157,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) { // also sink them down before their first use in the block. This xform has to // be careful not to *increase* register pressure though, e.g. sinking // "x = y + z" down if it kills y and z would increase the live ranges of y - // and z only the shrink the live range of x. + // and z and only shrink the live range of x. // Loop over all the operands of the specified instruction. If there is // anything we can't handle, bail out. |