diff options
| -rw-r--r-- | lib/CodeGen/LLVMTargetMachine.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp index 7f1a7c4f25..d437370031 100644 --- a/lib/CodeGen/LLVMTargetMachine.cpp +++ b/lib/CodeGen/LLVMTargetMachine.cpp @@ -330,6 +330,13 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM, PM.add(createOptimizePHIsPass()); // Delete dead machine instructions regardless of optimization level. + // + // At -O0, fast-isel frequently creates dead instructions. + // + // With optimization, dead code should already be eliminated. However + // there is one known exception: lowered code for arguments that are only + // used by tail calls, where the tail calls reuse the incoming stack + // arguments directly (see t11 in test/CodeGen/X86/sibcall.ll). PM.add(createDeadMachineInstructionElimPass()); printAndVerify(PM, "After codegen DCE pass", /* allowDoubleDefs= */ true); |