+ // If this is x86-64 and the Red Zone is not disabled, if we are a leaf
+ // function, and use up to 128 bytes of stack space, don't have a frame
+ // pointer, calls, or dynamic alloca then we do not need to adjust the
+ // stack pointer (we fit in the Red Zone).
+ if (Is64Bit && !DisableRedZone &&
+ !needsStackRealignment(MF) &&
+ !MFI->hasVarSizedObjects() && // No dynamic alloca.
+ !MFI->hasCalls()) { // No calls.
+ uint64_t MinSize = X86FI->getCalleeSavedFrameSize();
+ if (hasFP(MF)) MinSize += SlotSize;
+ StackSize = std::max(MinSize,
+ StackSize > 128 ? StackSize - 128 : 0);
+ MFI->setStackSize(StackSize);
+ }
+