Revert "ARM: Do not spill CSR to stack on entry to noreturn functions"

Breaks ubsan test TestCases/Misc/missing_return.cpp on ARM

This reverts commit r329287

llvm-svn: 329486

3 files changed, 0 insertions, 31 deletions

diff --git a/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp b/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
index 76c5425b692..79fafa5497f 100644
--- a/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
+++ b/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
@@ -36,12 +36,6 @@ bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
   return Attr.getValueAsString() == "true";
 }
 
-bool TargetFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
-  assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
-      MF.getFunction().hasFnAttribute(Attribute::NoUnwind));
-  return false;
-}
-
 /// Returns the displacement from the frame register to the stack
 /// frame of the specified index, along with the frame register used
 /// (in output arg FrameReg). This is the default implementation which
@@ -91,18 +85,6 @@ void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
   if (MF.getFunction().hasFnAttribute(Attribute::Naked))
     return;
 
-  // Noreturn+nounwind functions never restore CSR, so no saves are needed.
-  // Purely noreturn functions may still return through throws, so those must
-  // save CSR for caller exception handlers.
-  //
-  // If the function uses longjmp to break out of its current path of
-  // execution we do not need the CSR spills either: setjmp stores all CSRs
-  // it was called with into the jmp_buf, which longjmp then restores.
-  if (MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
-        MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
-        enableCalleeSaveSkip(MF))
-    return;
-
   // Functions which call __builtin_unwind_init get all their registers saved.
   bool CallsUnwindInit = MF.callsUnwindInit();
   const MachineRegisterInfo &MRI = MF.getRegInfo();
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index f9d2b606987..5da1e766a9e 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -87,17 +87,6 @@ bool ARMFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
          MF.getSubtarget<ARMSubtarget>().useFastISel();
 }
 
-/// Returns true if the target can safely skip saving callee-saved registers
-/// for noreturn nounwind functions.
-bool ARMFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
-  assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
-      MF.getFunction().hasFnAttribute(Attribute::NoUnwind));
-
-  // Frame pointer and link register are not treated as normal CSR, thus we
-  // can always skip CSR saves for nonreturning functions.
-  return true;
-}
-
 /// hasFP - Return true if the specified function should have a dedicated frame
 /// pointer register.  This is true if the function has variable sized allocas
 /// or if frame pointer elimination is disabled.
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.h b/llvm/lib/Target/ARM/ARMFrameLowering.h
index e994cab28fe..1f18e2bf80c 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.h
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.h
@@ -44,8 +44,6 @@ public:
 
   bool noFramePointerElim(const MachineFunction &MF) const override;
 
-  bool enableCalleeSaveSkip(const MachineFunction &MF) const override;
-
   bool hasFP(const MachineFunction &MF) const override;
   bool hasReservedCallFrame(const MachineFunction &MF) const override;
   bool canSimplifyCallFramePseudos(const MachineFunction &MF) const override;