Add a command-line flag to control the Swift extended async frame info.

Introduce a new command-line flag `-swift-async-fp={auto|always|never}`
that controls how code generation sets the Swift extended async frame
info bit. There are three possibilities:

* `auto`: which determines how to set the bit based on deployment target, either
statically or dynamically via `swift_async_extendedFramePointerFlags`.
* `always`: the default, always set the bit statically, regardless of deployment
target.
* `never`: never set the bit, regardless of deployment target.

Patch by Doug Gregor <dgregor@apple.com>

Reviewed By: doug.gregor

Differential Revision: https://reviews.llvm.org/D109392

7 files changed, 99 insertions, 29 deletions

diff --git a/llvm/include/llvm/CodeGen/CommandFlags.h b/llvm/include/llvm/CodeGen/CommandFlags.h
index 7ae951e..b0f1438 100644
--- a/llvm/include/llvm/CodeGen/CommandFlags.h
+++ b/llvm/include/llvm/CodeGen/CommandFlags.h
@@ -74,6 +74,8 @@ llvm::FloatABI::ABIType getFloatABIForCalls();
 
 llvm::FPOpFusion::FPOpFusionMode getFuseFPOps();
 
+SwiftAsyncFramePointerMode getSwiftAsyncFramePointer();
+
 bool getDontPlaceZerosInBSS();
 
 bool getEnableGuaranteedTailCallOpt();
diff --git a/llvm/include/llvm/Target/TargetOptions.h b/llvm/include/llvm/Target/TargetOptions.h
index a50da11..7f57108 100644
--- a/llvm/include/llvm/Target/TargetOptions.h
+++ b/llvm/include/llvm/Target/TargetOptions.h
@@ -110,6 +110,17 @@ namespace llvm {
     DisableWithDiag // Disable the abort but emit a diagnostic on failure.
   };
 
+  /// Indicates when and how the Swift async frame pointer bit should be set.
+  enum class SwiftAsyncFramePointerMode {
+    /// Determine whether to set the bit statically or dynamically based
+    /// on the deployment target.
+    DeploymentBased,
+    /// Always set the bit.
+    Always,
+    /// Never set the bit.
+    Never,
+  };
+
   class TargetOptions {
   public:
     TargetOptions()
@@ -219,6 +230,11 @@ namespace llvm {
     /// selection fails to lower/select an instruction.
     GlobalISelAbortMode GlobalISelAbort = GlobalISelAbortMode::Enable;
 
+    /// Control when and how the Swift async frame pointer bit should
+    /// be set.
+    SwiftAsyncFramePointerMode SwiftAsyncFramePointer =
+        SwiftAsyncFramePointerMode::Always;
+
     /// UseInitArray - Use .init_array instead of .ctors for static
     /// constructors.
     unsigned UseInitArray : 1;
diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
index c30e1c3..8f31630 100644
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -65,6 +65,7 @@ CGOPT(DenormalMode::DenormalModeKind, DenormalFP32Math)
 CGOPT(bool, EnableHonorSignDependentRoundingFPMath)
 CGOPT(FloatABI::ABIType, FloatABIForCalls)
 CGOPT(FPOpFusion::FPOpFusionMode, FuseFPOps)
+CGOPT(SwiftAsyncFramePointerMode, SwiftAsyncFramePointer)
 CGOPT(bool, DontPlaceZerosInBSS)
 CGOPT(bool, EnableGuaranteedTailCallOpt)
 CGOPT(bool, DisableTailCalls)
@@ -278,6 +279,18 @@ codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
                      "Only fuse FP ops when the result won't be affected.")));
   CGBINDOPT(FuseFPOps);
 
+  static cl::opt<SwiftAsyncFramePointerMode> SwiftAsyncFramePointer(
+      "swift-async-fp",
+      cl::desc("Determine when the Swift async frame pointer should be set"),
+      cl::init(SwiftAsyncFramePointerMode::Always),
+      cl::values(clEnumValN(SwiftAsyncFramePointerMode::DeploymentBased, "auto",
+                            "Determine based on deployment target"),
+                 clEnumValN(SwiftAsyncFramePointerMode::Always, "always",
+                            "Always set the bit"),
+                 clEnumValN(SwiftAsyncFramePointerMode::Never, "never",
+                            "Never set the bit")));
+  CGBINDOPT(SwiftAsyncFramePointer);
+
   static cl::opt<bool> DontPlaceZerosInBSS(
       "nozero-initialized-in-bss",
       cl::desc("Don't place zero-initialized symbols into bss section"),
@@ -539,7 +552,7 @@ codegen::InitTargetOptionsFromCodeGenFlags(const Triple &TheTriple) {
   Options.ThreadModel = getThreadModel();
   Options.EABIVersion = getEABIVersion();
   Options.DebuggerTuning = getDebuggerTuningOpt();
-
+  Options.SwiftAsyncFramePointer = getSwiftAsyncFramePointer();
   return Options;
 }
 
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 02421b8..9883f63 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1158,22 +1158,32 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
   // ORR is sufficient, it is assumed a Swift kernel would initialize the TBI
   // bits so that is still true.
   if (HasFP && AFI->hasSwiftAsyncContext()) {
-    if  (Subtarget.swiftAsyncContextIsDynamicallySet()) {
-      // The special symbol below is absolute and has a *value* that can be
-      // combined with the frame pointer to signal an extended frame.
-      BuildMI(MBB, MBBI, DL, TII->get(AArch64::LOADgot), AArch64::X16)
-          .addExternalSymbol("swift_async_extendedFramePointerFlags",
-                             AArch64II::MO_GOT);
-      BuildMI(MBB, MBBI, DL, TII->get(AArch64::ORRXrs), AArch64::FP)
-          .addUse(AArch64::FP)
-          .addUse(AArch64::X16)
-          .addImm(Subtarget.isTargetILP32() ? 32 : 0);
-    } else {
+    switch (MF.getTarget().Options.SwiftAsyncFramePointer) {
+    case SwiftAsyncFramePointerMode::DeploymentBased:
+      if (Subtarget.swiftAsyncContextIsDynamicallySet()) {
+        // The special symbol below is absolute and has a *value* that can be
+        // combined with the frame pointer to signal an extended frame.
+        BuildMI(MBB, MBBI, DL, TII->get(AArch64::LOADgot), AArch64::X16)
+            .addExternalSymbol("swift_async_extendedFramePointerFlags",
+                               AArch64II::MO_GOT);
+        BuildMI(MBB, MBBI, DL, TII->get(AArch64::ORRXrs), AArch64::FP)
+            .addUse(AArch64::FP)
+            .addUse(AArch64::X16)
+            .addImm(Subtarget.isTargetILP32() ? 32 : 0);
+        break;
+      }
+      LLVM_FALLTHROUGH;
+
+    case SwiftAsyncFramePointerMode::Always:
       // ORR x29, x29, #0x1000_0000_0000_0000
       BuildMI(MBB, MBBI, DL, TII->get(AArch64::ORRXri), AArch64::FP)
           .addUse(AArch64::FP)
           .addImm(0x1100)
           .setMIFlag(MachineInstr::FrameSetup);
+      break;
+
+    case SwiftAsyncFramePointerMode::Never:
+      break;
     }
   }
 
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 15d5f8b..56a4ebe 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -1364,22 +1364,32 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
   unsigned StackProbeSize = STI.getTargetLowering()->getStackProbeSize(MF);
 
   if (HasFP && X86FI->hasSwiftAsyncContext()) {
-    if (STI.swiftAsyncContextIsDynamicallySet()) {
-      // The special symbol below is absolute and has a *value* suitable to be
-      // combined with the frame pointer directly.
-      BuildMI(MBB, MBBI, DL, TII.get(X86::OR64rm), MachineFramePtr)
-          .addUse(MachineFramePtr)
-          .addUse(X86::RIP)
-          .addImm(1)
-          .addUse(X86::NoRegister)
-          .addExternalSymbol("swift_async_extendedFramePointerFlags",
-                             X86II::MO_GOTPCREL)
-          .addUse(X86::NoRegister);
-    } else {
+    switch (MF.getTarget().Options.SwiftAsyncFramePointer) {
+    case SwiftAsyncFramePointerMode::DeploymentBased:
+      if (STI.swiftAsyncContextIsDynamicallySet()) {
+        // The special symbol below is absolute and has a *value* suitable to be
+        // combined with the frame pointer directly.
+        BuildMI(MBB, MBBI, DL, TII.get(X86::OR64rm), MachineFramePtr)
+            .addUse(MachineFramePtr)
+            .addUse(X86::RIP)
+            .addImm(1)
+            .addUse(X86::NoRegister)
+            .addExternalSymbol("swift_async_extendedFramePointerFlags",
+                               X86II::MO_GOTPCREL)
+            .addUse(X86::NoRegister);
+        break;
+      }
+      LLVM_FALLTHROUGH;
+
+    case SwiftAsyncFramePointerMode::Always:
       BuildMI(MBB, MBBI, DL, TII.get(X86::BTS64ri8), MachineFramePtr)
           .addUse(MachineFramePtr)
           .addImm(60)
           .setMIFlag(MachineInstr::FrameSetup);
+      break;
+
+    case SwiftAsyncFramePointerMode::Never:
+      break;
     }
   }
 
diff --git a/llvm/test/CodeGen/AArch64/swift-dynamic-async-frame.ll b/llvm/test/CodeGen/AArch64/swift-dynamic-async-frame.ll
index 6b17b49..b6be40f 100644
--- a/llvm/test/CodeGen/AArch64/swift-dynamic-async-frame.ll
+++ b/llvm/test/CodeGen/AArch64/swift-dynamic-async-frame.ll
@@ -1,15 +1,24 @@
 ; RUN: llc -mtriple arm64-apple-ios15.0.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
-; RUN: llc -mtriple arm64-apple-ios14.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
+; RUN: llc -mtriple arm64-apple-ios15.0.0 -swift-async-fp=auto %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple arm64-apple-ios15.0.0 -swift-async-fp=never %s -o - | FileCheck %s --check-prefix=CHECK-NEVER
+; RUN: llc -mtriple arm64-apple-ios14.9.0 -swift-async-fp=always %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple arm64-apple-ios14.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple arm64-apple-ios14.9.0 -swift-async-fp=auto %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
 ; RUN: llc -mtriple arm64-apple-tvos15.0.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
-; RUN: llc -mtriple arm64-apple-tvos14.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
+; RUN: llc -mtriple arm64-apple-tvos14.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
 ; RUN: llc -mtriple arm64-apple-macosx12.0.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
-; RUN: llc -mtriple arm64-apple-macosx11.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
+; RUN: llc -mtriple arm64-apple-macosx11.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
 ; RUN: llc -mtriple arm64_32-apple-watchos8.0.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
-; RUN: llc -mtriple arm64_32-apple-watchos7.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC-32
+; RUN: llc -mtriple arm64_32-apple-watchos7.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple arm64_32-apple-watchos7.9.0 -swift-async-fp=auto %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC-32
 
 ; CHECK-STATIC-LABEL: foo:
 ; CHECK-STATIC: orr x29, x29, #0x1000000000000000
 
+; CHECK-NEVER-LABEL: foo:
+; CHECK-NEVER-NOT: orr x29, x29, #0x1000000000000000
+; CHECK-NEVER-NOT: _swift_async_extendedFramePointerFlags
+
 ; CHECK-DYNAMIC-LABEL: foo:
 ; CHECK-DYNAMIC: adrp x16, _swift_async_extendedFramePointerFlags@GOTPAGE
 ; CHECK-DYNAMIC: ldr x16, [x16, _swift_async_extendedFramePointerFlags@GOTPAGEOFF]
diff --git a/llvm/test/CodeGen/X86/swift-dynamic-async-frame.ll b/llvm/test/CodeGen/X86/swift-dynamic-async-frame.ll
index 8719aee..439b57e 100644
--- a/llvm/test/CodeGen/X86/swift-dynamic-async-frame.ll
+++ b/llvm/test/CodeGen/X86/swift-dynamic-async-frame.ll
@@ -1,5 +1,11 @@
 ; RUN: llc -mtriple x86_64-apple-macosx12.0.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
-; RUN: llc -mtriple x86_64-apple-macosx11.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
+; RUN: llc -mtriple x86_64-apple-macosx12.0.0 -swift-async-fp=always %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple x86_64-apple-macosx12.0.0 -swift-async-fp=auto %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple x86_64-apple-macosx11.9.0 -swift-async-fp=always %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple x86_64-apple-macosx11.9.0 %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple x86_64-apple-macosx11.9.0 -swift-async-fp=auto %s -o - | FileCheck %s --check-prefix=CHECK-DYNAMIC
+; RUN: llc -mtriple x86_64-apple-macosx11.9.0 -swift-async-fp=always %s -o - | FileCheck %s --check-prefix=CHECK-STATIC
+; RUN: llc -mtriple x86_64-apple-macosx11.9.0 -swift-async-fp=never %s -o - | FileCheck %s --check-prefix=CHECK-NEVER
 
 ; CHECK-STATIC-LABEL: foo:
 ; CHECK-STATIC: btsq $60, %rbp
@@ -7,6 +13,10 @@
 ; CHECK-DYNAMIC-LABEL: foo:
 ; CHECK-DYNAMIC: orq _swift_async_extendedFramePointerFlags@GOTPCREL(%rip), %rbp
 
+; CHECK-NEVER-LABEL: foo:
+; CHECK-NEVER-NOT: btsq $60, %rbp
+; CHECK-NEVER-NOT: _swift_async_extendedFramePointerFlags
+
 define void @foo(i8* swiftasync) "frame-pointer"="all" {
   ret void
 }