diff options
| author | Dan Gohman <gohman@apple.com> | 2010-06-24 23:41:59 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2010-06-24 23:41:59 +0000 |
| commit | 0879e2279025522a070d57a7c4e0122daef94e2f (patch) | |
| tree | 07604923ec5c57849f2809ee232529b6c78e700f /lib/CodeGen | |
| parent | 8b942977274e5e0940928e01699caf24075610ff (diff) | |
| download | external_llvm-0879e2279025522a070d57a7c4e0122daef94e2f.zip external_llvm-0879e2279025522a070d57a7c4e0122daef94e2f.tar.gz external_llvm-0879e2279025522a070d57a7c4e0122daef94e2f.tar.bz2 | |
Add some comments.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106809 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
| -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 7f1a7c4..d437370 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); |