InferAddressSpaces: Handle llvm.fake.use (#109567)

Author: arsenm

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

@@ -414,6 +414,10 @@ bool InferAddressSpacesImpl::rewriteIntrinsicOperands(IntrinsicInst *II,
     II->setCalledFunction(NewDecl);
     return true;
   }
+  case Intrinsic::fake_use: {
+    II->replaceUsesOfWith(OldV, NewV);
+    return true;
+  }
   default: {
     Value *Rewrite = TTI->rewriteIntrinsicWithAddressSpace(II, OldV, NewV);
     if (!Rewrite)
@@ -455,6 +459,16 @@ void InferAddressSpacesImpl::collectRewritableIntrinsicOperands(
     appendsFlatAddressExpressionToPostorderStack(II->getArgOperand(1),
                                                  PostorderStack, Visited);
     break;
+  case Intrinsic::fake_use: {
+    for (Value *Op : II->operands()) {
+      if (Op->getType()->isPtrOrPtrVectorTy()) {
+        appendsFlatAddressExpressionToPostorderStack(Op, PostorderStack,
+                                                     Visited);
+      }
+    }
+
+    break;
+  }
   default:
     SmallVector<int, 2> OpIndexes;
     if (TTI->collectFlatAddressOperands(OpIndexes, IID)) {

llvm/test/Transforms/InferAddressSpaces/fake-use.ll

@@ -0,0 +1,97 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=infer-address-spaces -assume-default-is-flat-addrspace %s | FileCheck %s
+
+declare void @llvm.fake.use(...)
+
+@gv = internal addrspace(3) global float 0.0, align 4
+
+define void @one_fake_use(ptr addrspace(1) %global.ptr) {
+; CHECK-LABEL: define void @one_fake_use(
+; CHECK-SAME: ptr addrspace(1) [[GLOBAL_PTR:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GLOBAL_PTR]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast ptr addrspace(1) %global.ptr to ptr
+  call void (...) @llvm.fake.use(ptr %cast0)
+  ret void
+}
+
+define void @one_fake_use_repeat_operands(ptr addrspace(1) %global.ptr) {
+; CHECK-LABEL: define void @one_fake_use_repeat_operands(
+; CHECK-SAME: ptr addrspace(1) [[GLOBAL_PTR:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GLOBAL_PTR]], ptr addrspace(1) [[GLOBAL_PTR]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast ptr addrspace(1) %global.ptr to ptr
+  call void (...) @llvm.fake.use(ptr %cast0, ptr %cast0)
+  ret void
+}
+
+define void @one_fake_use_refers_original_ptr(ptr addrspace(1) %global.ptr) {
+; CHECK-LABEL: define void @one_fake_use_refers_original_ptr(
+; CHECK-SAME: ptr addrspace(1) [[GLOBAL_PTR:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GLOBAL_PTR]], ptr addrspace(1) [[GLOBAL_PTR]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast ptr addrspace(1) %global.ptr to ptr
+  call void (...) @llvm.fake.use(ptr %cast0, ptr addrspace(1) %global.ptr)
+  ret void
+}
+
+define void @multiple_inferrable_fake_use(ptr addrspace(1) %global.ptr0, ptr addrspace(1) %global.ptr1) {
+; CHECK-LABEL: define void @multiple_inferrable_fake_use(
+; CHECK-SAME: ptr addrspace(1) [[GLOBAL_PTR0:%.*]], ptr addrspace(1) [[GLOBAL_PTR1:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GLOBAL_PTR0]], ptr addrspace(1) [[GLOBAL_PTR1]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast ptr addrspace(1) %global.ptr0 to ptr
+  %cast1 = addrspacecast ptr addrspace(1) %global.ptr1 to ptr
+  call void (...) @llvm.fake.use(ptr %cast0, ptr %cast1)
+  ret void
+}
+
+define void @multiple_fake_use_one_inferrable(ptr %flat.ptr0, ptr addrspace(1) %global.ptr1) {
+; CHECK-LABEL: define void @multiple_fake_use_one_inferrable(
+; CHECK-SAME: ptr [[FLAT_PTR0:%.*]], ptr addrspace(1) [[GLOBAL_PTR1:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr [[FLAT_PTR0]], ptr addrspace(1) [[GLOBAL_PTR1]])
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GLOBAL_PTR1]], ptr [[FLAT_PTR0]])
+; CHECK-NEXT:    ret void
+;
+  %cast1 = addrspacecast ptr addrspace(1) %global.ptr1 to ptr
+  call void (...) @llvm.fake.use(ptr %flat.ptr0, ptr %cast1)
+  call void (...) @llvm.fake.use(ptr %cast1, ptr %flat.ptr0)
+  ret void
+}
+
+define void @vector_of_pointers(<2 x ptr addrspace(1)> %global.ptr) {
+; CHECK-LABEL: define void @vector_of_pointers(
+; CHECK-SAME: <2 x ptr addrspace(1)> [[GLOBAL_PTR:%.*]]) {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(<2 x ptr addrspace(1)> [[GLOBAL_PTR]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast <2 x ptr addrspace(1)> %global.ptr to <2 x ptr>
+  call void (...) @llvm.fake.use(<2 x ptr> %cast0)
+  ret void
+}
+
+define void @use_global_var() {
+; CHECK-LABEL: define void @use_global_var() {
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(3) @gv)
+; CHECK-NEXT:    ret void
+;
+  call void (...) @llvm.fake.use(ptr addrspacecast (ptr addrspace(3) @gv to ptr))
+  ret void
+}
+
+define void @use_gep_cast(ptr addrspace(1) %global.ptr) {
+; CHECK-LABEL: define void @use_gep_cast(
+; CHECK-SAME: ptr addrspace(1) [[GLOBAL_PTR:%.*]]) {
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr addrspace(1) [[GLOBAL_PTR]], i64 16
+; CHECK-NEXT:    call void (...) @llvm.fake.use(ptr addrspace(1) [[GEP]], ptr addrspace(1) [[GLOBAL_PTR]])
+; CHECK-NEXT:    ret void
+;
+  %cast0 = addrspacecast ptr addrspace(1) %global.ptr to ptr
+  %gep = getelementptr i8, ptr %cast0, i64 16
+  call void (...) @llvm.fake.use(ptr %gep, ptr %cast0)
+  ret void
+}