Translate cmpxchg instruction in case it is followed by store inst (#865)

Author: vmaksimo

lib/SPIRV/SPIRVRegularizeLLVM.cpp

@@ -341,6 +341,10 @@ bool SPIRVRegularizeLLVM::regularize() {
           // OpIEqual instruction. The OpIEqual instruction returns true if the
           // original value equals to the comparator which matches with
           // semantics of cmpxchg.
+          // In case the original value was stored as is without extraction, we
+          // create a composite type manually from OpAtomicCompareExchange and
+          // OpIEqual instructions, and replace the original value usage in
+          // Store insruction with the new composite type.
           for (User *U : Cmpxchg->users()) {
             if (auto *Extract = dyn_cast<ExtractValueInst>(U)) {
               if (Extract->getIndices()[0] == 0) {
@@ -355,6 +359,14 @@ bool SPIRVRegularizeLLVM::regularize() {
               assert(Extract->user_empty());
               Extract->dropAllReferences();
               ToErase.push_back(Extract);
+            } else if (auto *Store = dyn_cast<StoreInst>(U)) {
+              auto *Cmp = new ICmpInst(Store, CmpInst::ICMP_EQ, Res, Comparator,
+                                       "cmpxchg.success");
+              auto *Agg = InsertValueInst::Create(
+                  UndefValue::get(Cmpxchg->getType()), Res, 0, "agg0", Store);
+              auto *AggStruct =
+                  InsertValueInst::Create(Agg, Cmp, 1, "agg1", Store);
+              Store->getValueOperand()->replaceAllUsesWith(AggStruct);
             }
           }
           if (Cmpxchg->user_empty())

test/AtomicCompareExchange.ll

@@ -7,6 +7,11 @@
 ; CHECK-SPIRV: Constant [[Int]] [[MemScope_Device:[0-9]+]] 1
 ; CHECK-SPIRV: Constant [[Int]] [[MemSemEqual_SeqCst:[0-9]+]] 16
 ; CHECK-SPIRV: Constant [[Int]] [[MemSemUnequal_Acquire:[0-9]+]] 2
+; CHECK-SPIRV: Constant [[Int]] [[Constant_456:[0-9]+]] 456
+; CHECK-SPIRV: Constant [[Int]] [[Constant_128:[0-9]+]] 128
+; CHECK-SPIRV: TypeBool [[Bool:[0-9]+]]
+; CHECK-SPIRV: TypeStruct [[Struct:[0-9]+]] [[Int]] [[Bool]]
+; CHECK-SPIRV: Undef [[Struct]] [[UndefStruct:[0-9]+]]
 
 ; CHECK-SPIRV: FunctionParameter {{[0-9]+}} [[Pointer:[0-9]+]]
 ; CHECK-SPIRV: FunctionParameter {{[0-9]+}} [[Value_ptr:[0-9]+]]
@@ -40,6 +45,24 @@ cmpxchg.continue:                                 ; preds = %cmpxchg.store_expec
   ret void
 }
 
+; CHECK-SPIRV: FunctionParameter {{[0-9]+}} [[Ptr:[0-9]+]]
+; CHECK-SPIRV: FunctionParameter {{[0-9]+}} [[Store_ptr:[0-9]+]]
+
+; CHECK-SPIRV: AtomicCompareExchange [[Int]] [[Res_1:[0-9]+]] [[Ptr]] [[MemScope_Device]]
+; CHECK-SPIRV-SAME:                  [[MemSemEqual_SeqCst]] [[MemSemUnequal_Acquire]] [[Constant_456]] [[Constant_128]]
+; CHECK-SPIRV: IEqual {{[0-9]+}} [[Success_1:[0-9]+]] [[Res_1]] [[Constant_128]]
+; CHECK-SPIRV: CompositeInsert [[Struct]] [[Composite:[0-9]+]] [[Res_1]] [[UndefStruct]] 0
+; CHECK-SPIRV: CompositeInsert [[Struct]] [[Composite_1:[0-9]+]] [[Success_1]] [[Composite]] 1
+; CHECK-SPIRV: Store [[Store_ptr]] [[Composite_1]]
+
+; Function Attrs: nounwind
+define dso_local spir_func void @test2(i32* %ptr, {i32, i1}* %store_ptr) local_unnamed_addr #0 {
+entry:
+  %0 = cmpxchg i32* %ptr, i32 128, i32 456 seq_cst acquire
+  store { i32, i1 } %0, { i32, i1 }* %store_ptr, align 4
+  ret void
+}
+
 attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
 attributes #1 = { nounwind }