diff options
Diffstat (limited to 'llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp')
| -rw-r--r-- | llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp index 6d19bddb38f..b77557ec122 100644 --- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp +++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp @@ -674,10 +674,14 @@ SystemZInstrInfo::foldMemoryOperandImpl(MachineFunction &MF, // // Although MVC is in practice a fast choice in these cases, it is still // logically a bytewise copy. This means that we cannot use it if the - // load or store is volatile. It also means that the transformation is - // not valid in cases where the two memories partially overlap; however, - // that is not a problem here, because we know that one of the memories - // is a full frame index. + // load or store is volatile. We also wouldn't be able to use MVC if + // the two memories partially overlap, but that case cannot occur here, + // because we know that one of the memories is a full frame index. + // + // For performance reasons, we also want to avoid using MVC if the addresses + // might be equal. We don't worry about that case here, because spill slot + // coloring happens later, and because we have special code to remove + // MVCs that turn out to be redundant. if (OpNum == 0 && MI->hasOneMemOperand()) { MachineMemOperand *MMO = *MI->memoperands_begin(); if (MMO->getSize() == Size && !MMO->isVolatile()) { |
