[BPF] Ensure GotoX only supported at CPU V4

Yonghong Song · Yonghong Song · commit c2022dd1ae8d · 2025-07-27T09:13:05.000-07:00
This is temporary and it makes easy to run bpf selftests.
Once kernel side is ready, we will implement CPU V5 which
will support jump tables.
diff --git a/llvm/lib/Target/BPF/BPFISelLowering.cpp b/llvm/lib/Target/BPF/BPFISelLowering.cpp
@@ -74,10 +74,14 @@ BPFTargetLowering::BPFTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::BR_JT, MVT::Other, Expand);
   setOperationAction(ISD::BRCOND, MVT::Other, Expand);
 
+  if (!STI.hasGotox())
+    setOperationAction(ISD::BRIND, MVT::Other, Expand);
+
   setOperationAction(ISD::TRAP, MVT::Other, Custom);
 
   setOperationAction({ISD::GlobalAddress, ISD::ConstantPool}, MVT::i64, Custom);
-  setOperationAction({ISD::JumpTable, ISD::BlockAddress}, MVT::i64, Custom);
+  if (STI.hasGotox())
+    setOperationAction({ISD::JumpTable, ISD::BlockAddress}, MVT::i64, Custom);
 
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i64, Custom);
   setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
diff --git a/llvm/lib/Target/BPF/BPFInstrInfo.td b/llvm/lib/Target/BPF/BPFInstrInfo.td
@@ -61,6 +61,7 @@ def BPFNoMovsx : Predicate<"!Subtarget->hasMovsx()">;
 def BPFNoBswap : Predicate<"!Subtarget->hasBswap()">;
 def BPFHasStoreImm : Predicate<"Subtarget->hasStoreImm()">;
 def BPFHasLoadAcqStoreRel : Predicate<"Subtarget->hasLoadAcqStoreRel()">;
+def BPFHasGotox : Predicate<"Subtarget->hasGotox()">;
 
 class ImmediateAsmOperand<string name> : AsmOperandClass {
   let Name = name;
@@ -294,8 +295,10 @@ defm JSLE : J<BPF_JSLE, "s<=", BPF_CC_LE, BPF_CC_LE_32>;
 defm JSET : J<BPF_JSET, "&", NoCond, NoCond>;
 def JCOND : JMP_JCOND<BPF_JCOND, "may_goto", []>;
 
-let isIndirectBranch = 1, isBarrier = 1 in {
-  def JX : JMP_IND<BPF_JA, "gotox", [(brind i64:$dst)]>;
+let Predicates = [BPFHasGotox] in {
+  let isIndirectBranch = 1, isBarrier = 1 in {
+    def JX : JMP_IND<BPF_JA, "gotox", [(brind i64:$dst)]>;
+  }
 }
 }
 
diff --git a/llvm/lib/Target/BPF/BPFSubtarget.cpp b/llvm/lib/Target/BPF/BPFSubtarget.cpp
@@ -43,6 +43,8 @@ static cl::opt<bool>
 static cl::opt<bool> Disable_load_acq_store_rel(
     "disable-load-acq-store-rel", cl::Hidden, cl::init(false),
     cl::desc("Disable load-acquire and store-release insns"));
+static cl::opt<bool> Disable_gotox("disable-gotox", cl::Hidden, cl::init(false),
+                                   cl::desc("Disable gotox insn"));
 
 void BPFSubtarget::anchor() {}
 
@@ -66,6 +68,7 @@ void BPFSubtarget::initializeEnvironment() {
   HasGotol = false;
   HasStoreImm = false;
   HasLoadAcqStoreRel = false;
+  HasGotox = false;
 }
 
 void BPFSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
@@ -96,6 +99,7 @@ void BPFSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
     HasGotol = !Disable_gotol;
     HasStoreImm = !Disable_StoreImm;
     HasLoadAcqStoreRel = !Disable_load_acq_store_rel;
+    HasGotox = !Disable_gotox;
     return;
   }
 }
diff --git a/llvm/lib/Target/BPF/BPFSubtarget.h b/llvm/lib/Target/BPF/BPFSubtarget.h
@@ -65,7 +65,7 @@ class BPFSubtarget : public BPFGenSubtargetInfo {
 
   // whether cpu v4 insns are enabled.
   bool HasLdsx, HasMovsx, HasBswap, HasSdivSmod, HasGotol, HasStoreImm,
-      HasLoadAcqStoreRel;
+      HasLoadAcqStoreRel, HasGotox;
 
   std::unique_ptr<CallLowering> CallLoweringInfo;
   std::unique_ptr<InstructionSelector> InstSelector;
@@ -94,6 +94,7 @@ class BPFSubtarget : public BPFGenSubtargetInfo {
   bool hasGotol() const { return HasGotol; }
   bool hasStoreImm() const { return HasStoreImm; }
   bool hasLoadAcqStoreRel() const { return HasLoadAcqStoreRel; }
+  bool hasGotox() const { return HasGotox; }
 
   bool isLittleEndian() const { return IsLittleEndian; }
 
