Make LLVMIsAtomicSingleThread work on non-atomic instructions.

Add LLVMIsAtomic so that users can guard uses of LLVMGetAtomicSyncScopeID.

Author: maleadt

llvm/include/llvm-c/Core.h

@@ -4630,7 +4630,13 @@ LLVMBool LLVMIsAtomicSingleThread(LLVMValueRef AtomicInst);
 void LLVMSetAtomicSingleThread(LLVMValueRef AtomicInst, LLVMBool SingleThread);
 
 /**
- * Returns the synchronization scope ID of an atomic instruction
+ * Returns whether an instruction is an atomic instruction, e.g., atomicrmw,
+ * cmpxchg, fence, or loads and stores with atomic ordering.
+ */
+LLVMBool LLVMIsAtomic(LLVMValueRef Inst);
+
+/**
+ * Returns the synchronization scope ID of an atomic instruction.
  */
 unsigned LLVMGetAtomicSyncScopeID(LLVMValueRef AtomicInst);
 

llvm/lib/IR/Core.cpp

@@ -4368,22 +4368,33 @@ int LLVMGetMaskValue(LLVMValueRef SVInst, unsigned Elt) {
 
 int LLVMGetUndefMaskElem(void) { return PoisonMaskElem; }
 
-LLVMBool LLVMIsAtomicSingleThread(LLVMValueRef AtomicInst) {
-  return getAtomicSyncScopeID(unwrap<Instruction>(AtomicInst)).value() ==
-         SyncScope::SingleThread;
+LLVMBool LLVMIsAtomic(LLVMValueRef Inst) {
+  return unwrap<Instruction>(Inst)->isAtomic();
 }
 
-unsigned LLVMGetAtomicSyncScopeID(LLVMValueRef AtomicInst) {
-  return getAtomicSyncScopeID(unwrap<Instruction>(AtomicInst)).value();
+LLVMBool LLVMIsAtomicSingleThread(LLVMValueRef AtomicInst) {
+  // Backwards compatibility: return false for non-atomic instructions
+  Instruction *I = unwrap<Instruction>(AtomicInst);
+  if (!I->isAtomic())
+    return 0;
+  return getAtomicSyncScopeID(I).value() == SyncScope::SingleThread;
 }
 
 void LLVMSetAtomicSingleThread(LLVMValueRef AtomicInst, LLVMBool NewValue) {
   SyncScope::ID SSID = NewValue ? SyncScope::SingleThread : SyncScope::System;
   setAtomicSyncScopeID(unwrap<Instruction>(AtomicInst), SSID);
 }
 
+unsigned LLVMGetAtomicSyncScopeID(LLVMValueRef AtomicInst) {
+  Instruction *I = unwrap<Instruction>(AtomicInst);
+  assert(I->isAtomic() && "Expected an atomic instruction");
+  return getAtomicSyncScopeID(I).value();
+}
+
 void LLVMSetAtomicSyncScopeID(LLVMValueRef AtomicInst, unsigned SSID) {
-  setAtomicSyncScopeID(unwrap<Instruction>(AtomicInst), SSID);
+  Instruction *I = unwrap<Instruction>(AtomicInst);
+  assert(I->isAtomic() && "Expected an atomic instruction");
+  setAtomicSyncScopeID(I, SSID);
 }
 
 LLVMAtomicOrdering LLVMGetCmpXchgSuccessOrdering(LLVMValueRef CmpXchgInst)  {

llvm/tools/llvm-c-test/echo.cpp

@@ -755,11 +755,13 @@ struct FunCloner {
         LLVMSetAlignment(Dst, LLVMGetAlignment(Src));
         LLVMSetOrdering(Dst, LLVMGetOrdering(Src));
         LLVMSetVolatile(Dst, LLVMGetVolatile(Src));
-        LLVMBool IsAtomicSingleThread = LLVMIsAtomicSingleThread(Src);
-        if (IsAtomicSingleThread)
-          LLVMSetAtomicSingleThread(Dst, IsAtomicSingleThread);
-        else
-          LLVMSetAtomicSyncScopeID(Dst, LLVMGetAtomicSyncScopeID(Src));
+        if (LLVMIsAtomic(Src)) {
+          LLVMBool IsAtomicSingleThread = LLVMIsAtomicSingleThread(Src);
+          if (IsAtomicSingleThread)
+            LLVMSetAtomicSingleThread(Dst, IsAtomicSingleThread);
+          else
+            LLVMSetAtomicSyncScopeID(Dst, LLVMGetAtomicSyncScopeID(Src));
+        }
         break;
       }
       case LLVMStore: {
@@ -769,11 +771,13 @@ struct FunCloner {
         LLVMSetAlignment(Dst, LLVMGetAlignment(Src));
         LLVMSetOrdering(Dst, LLVMGetOrdering(Src));
         LLVMSetVolatile(Dst, LLVMGetVolatile(Src));
-        LLVMBool IsAtomicSingleThread = LLVMIsAtomicSingleThread(Src);
-        if (IsAtomicSingleThread)
-          LLVMSetAtomicSingleThread(Dst, IsAtomicSingleThread);
-        else
-          LLVMSetAtomicSyncScopeID(Dst, LLVMGetAtomicSyncScopeID(Src));
+        if (LLVMIsAtomic(Src)) {
+          LLVMBool IsAtomicSingleThread = LLVMIsAtomicSingleThread(Src);
+          if (IsAtomicSingleThread)
+            LLVMSetAtomicSingleThread(Dst, IsAtomicSingleThread);
+          else
+            LLVMSetAtomicSyncScopeID(Dst, LLVMGetAtomicSyncScopeID(Src));
+        }
         break;
       }
       case LLVMGetElementPtr: {