[PATCH] D61799: Factor out redzone ABI checks [NFCI]

[Philip Reames via Phabricator via llvm-commits]

reames created this revision.
reames added reviewers: chandlerc, jfb, craig.topper.
Herald added subscribers: dexonsmith, bollu, mcrosier.
Herald added a project: LLVM.

As requested in D58632 <https://reviews.llvm.org/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.


Repository:
  rL LLVM

https://reviews.llvm.org/D61799

Files:
  lib/Target/X86/X86FrameLowering.cpp
  lib/Target/X86/X86FrameLowering.h
  lib/Target/X86/X86InstrInfo.cpp
  lib/Target/X86/X86SpeculativeLoadHardening.cpp


Index: lib/Target/X86/X86SpeculativeLoadHardening.cpp
===================================================================
--- lib/Target/X86/X86SpeculativeLoadHardening.cpp
+++ lib/Target/X86/X86SpeculativeLoadHardening.cpp
@@ -2465,7 +2465,7 @@
   // If we have no red zones or if the function returns twice (possibly without
   // using the `ret` instruction) like setjmp, we need to save the expected
   // return address prior to the call.
-  if (MF.getFunction().hasFnAttribute(Attribute::NoRedZone) ||
+  if (!Subtarget->getFrameLowering()->has128ByteRedZone(MF) ||
       MF.exposesReturnsTwice()) {
     // If we don't have red zones, we need to compute the expected return
     // address prior to the call and store it in a register that lives across
Index: lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- lib/Target/X86/X86InstrInfo.cpp
+++ lib/Target/X86/X86InstrInfo.cpp
@@ -7464,7 +7464,7 @@
 
   // Does the function use a red zone? If it does, then we can't risk messing
   // with the stack.
-  if (!F.hasFnAttribute(Attribute::NoRedZone)) {
+  if (Subtarget.getFrameLowering()->has128ByteRedZone(MF)) {
     // It could have a red zone. If it does, then we don't want to touch it.
     const X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
     if (!X86FI || X86FI->getUsesRedZone())
Index: lib/Target/X86/X86FrameLowering.h
===================================================================
--- lib/Target/X86/X86FrameLowering.h
+++ lib/Target/X86/X86FrameLowering.h
@@ -171,6 +171,10 @@
 
   unsigned getInitialCFARegister(const MachineFunction &MF) const override;
 
+  /// Return true if the function has a redzone (accessible bytes past the
+  /// frame of the top of stack function) as part of it's ABI.  
+  bool has128ByteRedZone(const MachineFunction& MF) const;
+
 private:
   uint64_t calculateMaxStackAlign(const MachineFunction &MF) const;
 
Index: lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- lib/Target/X86/X86FrameLowering.cpp
+++ lib/Target/X86/X86FrameLowering.cpp
@@ -872,6 +872,17 @@
   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 @@
       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 @@
   // 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();


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