[MachineOutliner] Don't outline functions starting with PATCHABLE_FUNCTION_ENTER/FENTRL_CALL

MachineOutliner may outline a "patchable-function-entry" function whose body has
a TargetOpcode::PATCHABLE_FUNCTION_ENTER MachineInstr. This is incorrect because
the special code sequence must stay unchanged to be used at run-time.
Avoid outlining PATCHABLE_FUNCTION_ENTER. While here, avoid outlining FENTRY_CALL too
(which doesn't reproduce currently) to allow phase ordering flexibility.

Fixes #52635

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D115614

(cherry picked from commit a6a07a514b8a084feaa7f4f15d569698b9840d83)

6 files changed, 208 insertions, 4 deletions

diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index 05d0591..35c3315 100644
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1922,9 +1922,7 @@ public:
   /// Optional target hook that returns true if \p MBB is safe to outline from,
   /// and returns any target-specific information in \p Flags.
   virtual bool isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
-                                      unsigned &Flags) const {
-    return true;
-  }
+                                      unsigned &Flags) const;
 
   /// Insert a custom frame for outlined functions.
   virtual void buildOutlinedFrame(MachineBasicBlock &MBB, MachineFunction &MF,
diff --git a/llvm/lib/CodeGen/TargetInstrInfo.cpp b/llvm/lib/CodeGen/TargetInstrInfo.cpp
index 2e4a656..4bbb5be 100644
--- a/llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ b/llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -1417,3 +1417,16 @@ std::string TargetInstrInfo::createMIROperandComment(
 }
 
 TargetInstrInfo::PipelinerLoopInfo::~PipelinerLoopInfo() {}
+
+bool TargetInstrInfo::isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
+                                             unsigned &Flags) const {
+  // Some instrumentations create special TargetOpcode at the start which
+  // expands to special code sequences which must be present.
+  auto First = MBB.getFirstNonDebugInstr();
+  if (First != MBB.end() &&
+      (First->getOpcode() == TargetOpcode::FENTRY_CALL ||
+       First->getOpcode() == TargetOpcode::PATCHABLE_FUNCTION_ENTER))
+    return false;
+
+  return true;
+}
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index 091a62a..f29bb83 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -6923,6 +6923,8 @@ bool AArch64InstrInfo::isFunctionSafeToOutlineFrom(
 
 bool AArch64InstrInfo::isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
                                               unsigned &Flags) const {
+  if (!TargetInstrInfo::isMBBSafeToOutlineFrom(MBB, Flags))
+    return false;
   // Check if LR is available through all of the MBB. If it's not, then set
   // a flag.
   assert(MBB.getParent()->getRegInfo().tracksLiveness() &&
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
index 2071017..7dab7a5 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -999,7 +999,7 @@ bool RISCVInstrInfo::isFunctionSafeToOutlineFrom(
 bool RISCVInstrInfo::isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
                                             unsigned &Flags) const {
   // More accurate safety checking is done in getOutliningCandidateInfo.
-  return true;
+  return TargetInstrInfo::isMBBSafeToOutlineFrom(MBB, Flags);
 }
 
 // Enum values indicating how an outlined call should be constructed.
diff --git a/llvm/test/CodeGen/AArch64/machine-outliner-patchable.ll b/llvm/test/CodeGen/AArch64/machine-outliner-patchable.ll
new file mode 100644
index 0000000..e381b49
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/machine-outliner-patchable.ll
@@ -0,0 +1,114 @@
+; RUN: llc < %s -verify-machineinstrs -enable-machine-outliner | FileCheck %s
+
+target triple = "aarch64-unknown-linux-gnu"
+
+declare void @foo(i32, i32, i32, i32) minsize
+
+;; TargetOpcode::FENTRY_CALL at the start of the function expands to a __fentry__
+;; call which must be present. Don't outline it.
+define void @fentry0(i1 %a) nounwind "fentry-call"="true" {
+; CHECK-LABEL: fentry0:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:    # FEntry call
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+define void @fentry1(i1 %a) nounwind "fentry-call"="true" {
+; CHECK-LABEL: fentry1:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:    # FEntry call
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+;; TargetOpcode::PATCHABLE_FUNCTION_ENTER at the start of the function expands to
+;; NOPs which must be present. Don't outline them.
+define void @patchable0(i1 %a) nounwind "patchable-function-entry"="2" {
+; CHECK-LABEL: patchable0:
+; CHECK-NEXT:  .Lfunc_begin0:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    nop
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+define void @patchable1(i1 %a) nounwind "patchable-function-entry"="2" {
+; CHECK-LABEL: patchable1:
+; CHECK-NEXT:  .Lfunc_begin1:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    nop
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+;; Similar to "patchable-function-entry".
+define void @xray0(i1 %a) nounwind "function-instrument"="xray-always" {
+; CHECK-LABEL: xray0:
+; CHECK-NEXT:  .Lfunc_begin2:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:  .p2align 2
+; CHECK-NEXT:  .Lxray_sled_0:
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+define void @xray1(i1 %a) nounwind "function-instrument"="xray-always" {
+; CHECK-LABEL: xray1:
+; CHECK-NEXT:  .Lfunc_begin3:
+; CHECK-NEXT:  // %bb.0:
+; CHECK-NEXT:  .p2align 2
+; CHECK-NEXT:  .Lxray_sled_2:
+; CHECK:       // %bb.1:
+; CHECK-NEXT:    bl OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
diff --git a/llvm/test/CodeGen/RISCV/machine-outliner-patchable.ll b/llvm/test/CodeGen/RISCV/machine-outliner-patchable.ll
new file mode 100644
index 0000000..4ef3abd
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/machine-outliner-patchable.ll
@@ -0,0 +1,77 @@
+; RUN: llc < %s -verify-machineinstrs -enable-machine-outliner | FileCheck %s
+
+target triple = "riscv64-unknown-linux-gnu"
+
+declare void @foo(i32, i32, i32, i32) minsize
+
+;; TargetOpcode::FENTRY_CALL at the start of the function expands to a __fentry__
+;; call which must be present. Don't outline it.
+define void @fentry0(i1 %a) nounwind "fentry-call"="true" {
+; CHECK-LABEL: fentry0:
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    # FEntry call
+; CHECK:       # %bb.1:
+; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+define void @fentry1(i1 %a) nounwind "fentry-call"="true" {
+; CHECK-LABEL: fentry1:
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    # FEntry call
+; CHECK:       # %bb.1:
+; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+;; TargetOpcode::PATCHABLE_FUNCTION_ENTER at the start of the function expands to
+;; NOPs which must be present. Don't outline them.
+define void @patchable0(i1 %a) nounwind "patchable-function-entry"="2" {
+; CHECK-LABEL: patchable0:
+; CHECK-NEXT:  .Lfunc_begin0:
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    nop
+; CHECK:       # %bb.1:
+; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}
+
+define void @patchable1(i1 %a) nounwind "patchable-function-entry"="2" {
+; CHECK-LABEL: patchable1:
+; CHECK-NEXT:  .Lfunc_begin1:
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    nop
+; CHECK:       # %bb.1:
+; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_1
+entry:
+  br i1 %a, label %if.then, label %if.end
+if.then:
+  call void @foo(i32 1, i32 2, i32 3, i32 4)
+  br label %if.end
+if.end:
+  call void @foo(i32 5, i32 6, i32 7, i32 8)
+  ret void
+}