Replace "no-frame-pointer-*" function attributes with "frame-pointer"

Part of the effort to refactoring frame pointer code generation. We used
to use two function attributes "no-frame-pointer-elim" and
"no-frame-pointer-elim-non-leaf" to represent three kinds of frame
pointer usage: (all) frames use frame pointer, (non-leaf) frames use
frame pointer, (none) frame use frame pointer. This CL makes the idea
explicit by using only one enum function attribute "frame-pointer"

Option "-frame-pointer=" replaces "-disable-fp-elim" for tools such as
llc.

"no-frame-pointer-elim" and "no-frame-pointer-elim-non-leaf" are still
supported for easy migration to "frame-pointer".

tests are mostly updated with

// replace command line args ‘-disable-fp-elim=false’ with ‘-frame-pointer=none’
grep -iIrnl '\-disable-fp-elim=false' * | xargs sed -i '' -e "s/-disable-fp-elim=false/-frame-pointer=none/g"

// replace command line args ‘-disable-fp-elim’ with ‘-frame-pointer=all’
grep -iIrnl '\-disable-fp-elim' * | xargs sed -i '' -e "s/-disable-fp-elim/-frame-pointer=all/g"

Patch by Yuanfang Chen (tabloid.adroit)!

Differential Revision: https://reviews.llvm.org/D56351

llvm-svn: 351049

4 files changed, 28 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp b/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
index f0cfa2fbe4f..cf78fb5a1f1 100644
--- a/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
+++ b/llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
@@ -30,12 +30,6 @@ using namespace llvm;
 
 TargetFrameLowering::~TargetFrameLowering() = default;
 
-/// The default implementation just looks at attribute "no-frame-pointer-elim".
-bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
-  auto Attr = MF.getFunction().getFnAttribute("no-frame-pointer-elim");
-  return Attr.getValueAsString() == "true";
-}
-
 bool TargetFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
   assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
          MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
diff --git a/llvm/lib/CodeGen/TargetOptionsImpl.cpp b/llvm/lib/CodeGen/TargetOptionsImpl.cpp
index 853e71d0efa..3c133fb8594 100644
--- a/llvm/lib/CodeGen/TargetOptionsImpl.cpp
+++ b/llvm/lib/CodeGen/TargetOptionsImpl.cpp
@@ -23,15 +23,34 @@ using namespace llvm;
 /// DisableFramePointerElim - This returns true if frame pointer elimination
 /// optimization should be disabled for the given machine function.
 bool TargetOptions::DisableFramePointerElim(const MachineFunction &MF) const {
-  // Check to see if we should eliminate all frame pointers.
-  if (MF.getSubtarget().getFrameLowering()->noFramePointerElim(MF))
+  // Check to see if the target want to forcably keep frame pointer.
+  if (MF.getSubtarget().getFrameLowering()->keepFramePointer(MF))
     return true;
 
-  // Check to see if we should eliminate non-leaf frame pointers.
-  if (MF.getFunction().hasFnAttribute("no-frame-pointer-elim-non-leaf"))
-    return MF.getFrameInfo().hasCalls();
+  const Function &F = MF.getFunction();
+
+  // TODO: Remove support for old `fp elim` function attributes after fully
+  //       migrate to use "frame-pointer"
+  if (!F.hasFnAttribute("frame-pointer")) {
+    // Check to see if we should eliminate all frame pointers.
+    if (F.getFnAttribute("no-frame-pointer-elim").getValueAsString() == "true")
+      return true;
+
+    // Check to see if we should eliminate non-leaf frame pointers.
+    if (F.hasFnAttribute("no-frame-pointer-elim-non-leaf"))
+      return MF.getFrameInfo().hasCalls();
 
-  return false;
+    return false;
+  }
+
+  StringRef FP = F.getFnAttribute("frame-pointer").getValueAsString();
+  if (FP == "all")
+    return true;
+  if (FP == "non-leaf")
+    return MF.getFrameInfo().hasCalls();
+  if (FP == "none")
+    return false;
+  llvm_unreachable("unknown frame pointer flag");
 }
 
 /// HonorSignDependentRoundingFPMath - Return true if the codegen must assume
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index 2417166ca96..a9d87ced31f 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -79,12 +79,11 @@ ARMFrameLowering::ARMFrameLowering(const ARMSubtarget &sti)
     : TargetFrameLowering(StackGrowsDown, sti.getStackAlignment(), 0, 4),
       STI(sti) {}
 
-bool ARMFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
+bool ARMFrameLowering::keepFramePointer(const MachineFunction &MF) const {
   // iOS always has a FP for backtracking, force other targets to keep their FP
   // when doing FastISel. The emitted code is currently superior, and in cases
   // like test-suite's lencod FastISel isn't quite correct when FP is eliminated.
-  return TargetFrameLowering::noFramePointerElim(MF) ||
-         MF.getSubtarget<ARMSubtarget>().useFastISel();
+  return MF.getSubtarget<ARMSubtarget>().useFastISel();
 }
 
 /// Returns true if the target can safely skip saving callee-saved registers
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.h b/llvm/lib/Target/ARM/ARMFrameLowering.h
index e994cab28fe..2f7e23840e7 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.h
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.h
@@ -42,7 +42,7 @@ public:
                                   std::vector<CalleeSavedInfo> &CSI,
                                   const TargetRegisterInfo *TRI) const override;
 
-  bool noFramePointerElim(const MachineFunction &MF) const override;
+  bool keepFramePointer(const MachineFunction &MF) const override;
 
   bool enableCalleeSaveSkip(const MachineFunction &MF) const override;