Factor out redzone ABI checks [NFCI]

As requested in D58632, cleanup our red zone detection logic in the X86 backend. The existing X86MachineFunctionInfo flag is used to track whether we *use* the redzone (via a particularly optimization?), but there's no common way to check whether the function *has* a red zone.

I'd appreciate careful review of the uses being updated. I think they are NFC, but a careful eye from someone else would be appreciated.

Differential Revision: https://reviews.llvm.org/D61799

llvm-svn: 360479

1 files changed, 12 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index f4ef796e80c..f52bb2f4203 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -872,6 +872,17 @@ void X86FrameLowering::BuildStackAlignAND(MachineBasicBlock &MBB,
   MI->getOperand(3).setIsDead();
 }
 
+bool X86FrameLowering::has128ByteRedZone(const MachineFunction& MF) const {
+  // x86-64 (non Win64) has a 128 byte red zone which is guaranteed not to be
+  // clobbered by any interrupt handler.   
+  assert(&STI == &MF.getSubtarget<X86Subtarget>() &&
+         "MF used frame lowering for wrong subtarget");
+  const Function &Fn = MF.getFunction();
+  const bool IsWin64CC = STI.isCallingConvWin64(Fn.getCallingConv());
+  return Is64Bit && !IsWin64CC && !Fn.hasFnAttribute(Attribute::NoRedZone);
+}
+
+
 /// emitPrologue - Push callee-saved registers onto the stack, which
 /// automatically adjust the stack pointer. Adjust the stack pointer to allocate
 /// space for local variables. Also emit labels used by the exception handler to
@@ -976,7 +987,6 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
       MF.hasEHFunclets() && Personality == EHPersonality::CoreCLR;
   bool IsClrFunclet = IsFunclet && FnHasClrFunclet;
   bool HasFP = hasFP(MF);
-  bool IsWin64CC = STI.isCallingConvWin64(Fn.getCallingConv());
   bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
   bool NeedsWin64CFI = IsWin64Prologue && Fn.needsUnwindTableEntry();
   // FIXME: Emit FPO data for EH funclets.
@@ -1030,12 +1040,11 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
   // pointer, calls, or dynamic alloca then we do not need to adjust the
   // stack pointer (we fit in the Red Zone). We also check that we don't
   // push and pop from the stack.
-  if (Is64Bit && !Fn.hasFnAttribute(Attribute::NoRedZone) &&
+  if (has128ByteRedZone(MF) &&
       !TRI->needsStackRealignment(MF) &&
       !MFI.hasVarSizedObjects() &&             // No dynamic alloca.
       !MFI.adjustsStack() &&                   // No calls.
       !UseStackProbe &&                        // No stack probes.
-      !IsWin64CC &&                            // Win64 has no Red Zone
       !MFI.hasCopyImplyingStackAdjustment() && // Don't push and pop.
       !MF.shouldSplitStack()) {                // Regular stack
     uint64_t MinSize = X86FI->getCalleeSavedFrameSize();