Index: llvm/lib/Target/AMDGPU/AMDGPULibFunc.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPULibFunc.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPULibFunc.cpp
@@ -954,13 +954,16 @@
   std::string FuncName = fInfo.mangle();
   Function *F = dyn_cast_or_null<Function>(
     M->getValueSymbolTable().lookup(FuncName));
+  if (!F || F->isDeclaration())
+    return nullptr;
 
-  // check formal with actual types conformance
-  if (F && !F->isDeclaration() &&
-      fInfo.isCompatibleSignature(F->getFunctionType()))
-    return F;
+  if (F->hasFnAttribute(Attribute::NoBuiltin))
+    return nullptr;
 
-  return nullptr;
+  if (!fInfo.isCompatibleSignature(F->getFunctionType()))
+    return nullptr;
+
+  return F;
 }
 
 FunctionCallee AMDGPULibFunc::getOrInsertFunction(Module *M,
@@ -969,10 +972,13 @@
   Function *F = dyn_cast_or_null<Function>(
     M->getValueSymbolTable().lookup(FuncName));
 
-  // check formal with actual types conformance
-  if (F && !F->isDeclaration() &&
-      fInfo.isCompatibleSignature(F->getFunctionType()))
-    return F;
+  if (F) {
+    if (F->hasFnAttribute(Attribute::NoBuiltin))
+      return nullptr;
+    if (!F->isDeclaration() &&
+        fInfo.isCompatibleSignature(F->getFunctionType()))
+      return F;
+  }
 
   FunctionType *FuncTy = fInfo.getFunctionType(*M);
 
Index: llvm/test/CodeGen/AMDGPU/simplify-libcall-nobuiltin-def.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/simplify-libcall-nobuiltin-def.ll
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -S -mtriple=amdgcn-- -passes=amdgpu-usenative -amdgpu-use-native=all < %s | FileCheck %s
+
+; Verify nobuiltin is respected on a defined function. native_cos is
+; marked nobuiltin, but native_sin is not.
+
+define float @_Z10native_sinf(float %x) {
+; CHECK-LABEL: define float @_Z10native_sinf
+; CHECK-SAME: (float [[X:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float asm "
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float asm "; $0 = native_sin($1)", "=v,v"(float %x)
+  ret float %result
+}
+
+define float @_Z10native_cosf(float %x) nobuiltin {
+; CHECK-LABEL: define float @_Z10native_cosf
+; CHECK-SAME: (float [[X:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float asm "
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float asm "; $0 = native_cos($1)", "=v,v"(float %x)
+  ret float %result
+}
+
+define float @_Z3sinf(float %x) {
+; CHECK-LABEL: define float @_Z3sinf
+; CHECK-SAME: (float [[X:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float asm "
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float asm "; $0 = sin($1)", "=v,v"(float %x)
+  ret float %result
+}
+
+define float @_Z3cosf(float %x) {
+; CHECK-LABEL: define float @_Z3cosf
+; CHECK-SAME: (float [[X:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float asm "
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float asm "; $0 = cos($1)", "=v,v"(float %x)
+  ret float %result
+}
+
+define float @call_cos(float %x) {
+; CHECK-LABEL: define float @call_cos
+; CHECK-SAME: (float [[X:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float @_Z3cosf(float [[X]])
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float @_Z3cosf(float %x)
+  ret float %result
+}
+
+define float @call_sin(float %x) {
+; CHECK-LABEL: define float @call_sin
+; CHECK-SAME: (float [[X:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float @_Z10native_sinf(float [[X]])
+; CHECK-NEXT:    ret float [[RESULT]]
+;
+  %result = call float @_Z3sinf(float %x)
+  ret float %result
+}