[C API] Fix LLVMGetOrdering/LLVMIsAtomicSingleThread for fence/memory instrs

LLVMGetOrdering previously did not support Fence instructions, and calling it
on a fence would lead to a bad cast as it assumed a load/store, or an
AtomicRMWInst. This would either read a garbage memory order, or assertion

LLVMIsAtomicSingleThread did not support either Fence instructions, loads, or
stores, and would similarly lead to a bad cast

These cases are now fixed for the C API, and tests for these instructions are
added. The echo test utility now also supports cloning Fence instructions,
which it did not previously

Author: Benjins

llvm/lib/IR/Core.cpp

@@ -3758,6 +3758,8 @@ LLVMAtomicOrdering LLVMGetOrdering(LLVMValueRef MemAccessInst) {
     O = LI->getOrdering();
   else if (StoreInst *SI = dyn_cast<StoreInst>(P))
     O = SI->getOrdering();
+  else if (FenceInst *FI = dyn_cast<FenceInst>(P))
+    O = FI->getOrdering();
   else
     O = cast<AtomicRMWInst>(P)->getOrdering();
   return mapToLLVMOrdering(O);
@@ -3769,6 +3771,8 @@ void LLVMSetOrdering(LLVMValueRef MemAccessInst, LLVMAtomicOrdering Ordering) {
 
   if (LoadInst *LI = dyn_cast<LoadInst>(P))
     return LI->setOrdering(O);
+  else if (FenceInst *FI = dyn_cast<FenceInst>(P))
+    return FI->setOrdering(O);
   return cast<StoreInst>(P)->setOrdering(O);
 }
 
@@ -4039,6 +4043,12 @@ LLVMBool LLVMIsAtomicSingleThread(LLVMValueRef AtomicInst) {
 
   if (AtomicRMWInst *I = dyn_cast<AtomicRMWInst>(P))
     return I->getSyncScopeID() == SyncScope::SingleThread;
+  else if (FenceInst *FI = dyn_cast<FenceInst>(P))
+    return FI->getSyncScopeID() == SyncScope::SingleThread;
+  else if (StoreInst *SI = dyn_cast<StoreInst>(P))
+    return SI->getSyncScopeID() == SyncScope::SingleThread;
+  else if (LoadInst *LI = dyn_cast<LoadInst>(P))
+    return LI->getSyncScopeID() == SyncScope::SingleThread;
   return cast<AtomicCmpXchgInst>(P)->getSyncScopeID() ==
              SyncScope::SingleThread;
 }
@@ -4049,6 +4059,12 @@ void LLVMSetAtomicSingleThread(LLVMValueRef AtomicInst, LLVMBool NewValue) {
 
   if (AtomicRMWInst *I = dyn_cast<AtomicRMWInst>(P))
     return I->setSyncScopeID(SSID);
+  else if (FenceInst *FI = dyn_cast<FenceInst>(P))
+    return FI->setSyncScopeID(SSID);
+  else if (StoreInst *SI = dyn_cast<StoreInst>(P))
+    return SI->setSyncScopeID(SSID);
+  else if (LoadInst *LI = dyn_cast<LoadInst>(P))
+    return LI->setSyncScopeID(SSID);
   return cast<AtomicCmpXchgInst>(P)->setSyncScopeID(SSID);
 }
 

llvm/test/Bindings/llvm-c/atomics.ll

@@ -2,6 +2,40 @@
 ; RUN: llvm-as < %s | llvm-c-test --echo > %t.echo
 ; RUN: diff -w %t.orig %t.echo
 
+
+define void @fence_instrs() {
+  fence acquire
+  fence release
+  fence acq_rel
+  fence seq_cst
+
+  fence syncscope("singlethread") acquire
+  fence syncscope("singlethread") release
+  fence syncscope("singlethread") acq_rel
+  fence syncscope("singlethread") seq_cst
+
+  ret void
+}
+
+define void @atomic_load_store(ptr %word) {
+  ; Test different atomic loads
+  %ld.1 = load atomic i32, ptr %word monotonic, align 4
+  %ld.2 = load atomic volatile i32, ptr %word acquire, align 4
+  %ld.3 = load atomic volatile i32, ptr %word seq_cst, align 4
+  %ld.4 = load atomic volatile i32, ptr %word syncscope("singlethread") acquire, align 4
+  %ld.5 = load atomic volatile i32, ptr %word syncscope("singlethread") seq_cst, align 4
+  %ld.6 = load atomic i32, ptr %word syncscope("singlethread") seq_cst, align 4
+
+  ; Test different atomic stores
+  store atomic i32 1, ptr %word monotonic, align 4
+  store atomic volatile i32 2, ptr %word release, align 4
+  store atomic volatile i32 3, ptr %word seq_cst, align 4
+  store atomic volatile i32 4, ptr %word syncscope("singlethread") release, align 4
+  store atomic volatile i32 5, ptr %word syncscope("singlethread") seq_cst, align 4
+  store atomic i32 6, ptr %word syncscope("singlethread") seq_cst, align 4
+  ret void
+}
+
 define i32 @main() {
   %1 = alloca i32, align 4
   %2 = cmpxchg ptr %1, i32 2, i32 3 seq_cst acquire

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

@@ -677,6 +677,7 @@ struct FunCloner {
         LLVMSetAlignment(Dst, LLVMGetAlignment(Src));
         LLVMSetOrdering(Dst, LLVMGetOrdering(Src));
         LLVMSetVolatile(Dst, LLVMGetVolatile(Src));
+        LLVMSetAtomicSingleThread(Dst, LLVMIsAtomicSingleThread(Src));
         break;
       }
       case LLVMStore: {
@@ -686,6 +687,7 @@ struct FunCloner {
         LLVMSetAlignment(Dst, LLVMGetAlignment(Src));
         LLVMSetOrdering(Dst, LLVMGetOrdering(Src));
         LLVMSetVolatile(Dst, LLVMGetVolatile(Src));
+        LLVMSetAtomicSingleThread(Dst, LLVMIsAtomicSingleThread(Src));
         break;
       }
       case LLVMGetElementPtr: {
@@ -891,6 +893,12 @@ struct FunCloner {
         Dst = LLVMBuildFreeze(Builder, Arg, Name);
         break;
       }
+      case LLVMFence: {
+        LLVMAtomicOrdering Ordering = LLVMGetOrdering(Src);
+        LLVMBool IsSingleThreaded = LLVMIsAtomicSingleThread(Src);
+        Dst = LLVMBuildFence(Builder, Ordering, IsSingleThreaded, Name);
+        break;
+      }
       default:
         break;
     }