[WebAssembly] Improve clang diagnostics for wasm attributes

This patch addresses the review comments on r352930:

 - Removes redundant diagnostic checking code
 - Removes errnoneous use of diag::err_alias_is_definition, which
   turned out to be ineffective anyway since functions can be defined later
   in the translation unit and avoid detection.
 - Adds a test for various invalid cases for import_name and import_module.

This reapplies D59520, with the addition of adding
`InGroup<IgnoredAttributes>` to the new warnings, to fix the
Misc/warning-flags.c failure.

Differential Revision: https://reviews.llvm.org/D59520

Author: sunfishcode

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10770,6 +10770,14 @@ def err_matrix_separate_incomplete_index: Error<
 def err_matrix_subscript_comma: Error<
   "comma expressions are not allowed as indices in matrix subscript expressions">;
 
+def warn_mismatched_import : Warning<
+  "import %select{module|name}0 (%1) does not match the import %select{module|name}0 (%2) of the "
+  "previous declaration">,
+  InGroup<IgnoredAttributes>;
+def warn_import_on_definition : Warning<
+  "import %select{module|name}0 cannot be applied to a function with a definition">,
+  InGroup<IgnoredAttributes>;
+
 def err_preserve_field_info_not_field : Error<
   "__builtin_preserve_field_info argument %0 not a field access">;
 def err_preserve_field_info_not_const: Error<

clang/include/clang/Sema/Sema.h

@@ -2999,6 +2999,10 @@ class Sema final {
                                                 const InternalLinkageAttr &AL);
   CommonAttr *mergeCommonAttr(Decl *D, const ParsedAttr &AL);
   CommonAttr *mergeCommonAttr(Decl *D, const CommonAttr &AL);
+  WebAssemblyImportNameAttr *mergeImportNameAttr(
+      Decl *D, const WebAssemblyImportNameAttr &AL);
+  WebAssemblyImportModuleAttr *mergeImportModuleAttr(
+      Decl *D, const WebAssemblyImportModuleAttr &AL);
 
   void mergeDeclAttributes(NamedDecl *New, Decl *Old,
                            AvailabilityMergeKind AMK = AMK_Redeclaration);

clang/lib/Sema/SemaDecl.cpp

@@ -2598,6 +2598,10 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
     NewAttr = S.mergeSpeculativeLoadHardeningAttr(D, *SLHA);
   else if (const auto *SLHA = dyn_cast<NoSpeculativeLoadHardeningAttr>(Attr))
     NewAttr = S.mergeNoSpeculativeLoadHardeningAttr(D, *SLHA);
+  else if (const auto *IMA = dyn_cast<WebAssemblyImportModuleAttr>(Attr))
+    NewAttr = S.mergeImportModuleAttr(D, *IMA);
+  else if (const auto *INA = dyn_cast<WebAssemblyImportNameAttr>(Attr))
+    NewAttr = S.mergeImportNameAttr(D, *INA);
   else if (Attr->shouldInheritEvenIfAlreadyPresent() || !DeclHasAttr(D, Attr))
     NewAttr = cast<InheritableAttr>(Attr->clone(S.Context));
 

clang/lib/Sema/SemaDeclAttr.cpp

@@ -5892,45 +5892,75 @@ static void handleWebAssemblyExportNameAttr(Sema &S, Decl *D, const ParsedAttr &
   D->addAttr(UsedAttr::CreateImplicit(S.Context));
 }
 
-static void handleWebAssemblyImportModuleAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
-  if (!isFunctionOrMethod(D)) {
-    S.Diag(D->getLocation(), diag::warn_attribute_wrong_decl_type)
-        << "'import_module'" << ExpectedFunction;
-    return;
+WebAssemblyImportModuleAttr *
+Sema::mergeImportModuleAttr(Decl *D, const WebAssemblyImportModuleAttr &AL) {
+  auto *FD = cast<FunctionDecl>(D);
+
+  if (const auto *ExistingAttr = FD->getAttr<WebAssemblyImportModuleAttr>()) {
+    if (ExistingAttr->getImportModule() == AL.getImportModule())
+      return nullptr;
+    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_import) << 0
+      << ExistingAttr->getImportModule() << AL.getImportModule();
+    Diag(AL.getLoc(), diag::note_previous_attribute);
+    return nullptr;
+  }
+  if (FD->hasBody()) {
+    Diag(AL.getLoc(), diag::warn_import_on_definition) << 0;
+    return nullptr;
   }
+  return ::new (Context) WebAssemblyImportModuleAttr(Context, AL,
+                                                     AL.getImportModule());
+}
 
+WebAssemblyImportNameAttr *
+Sema::mergeImportNameAttr(Decl *D, const WebAssemblyImportNameAttr &AL) {
   auto *FD = cast<FunctionDecl>(D);
-  if (FD->isThisDeclarationADefinition()) {
-    S.Diag(D->getLocation(), diag::err_alias_is_definition) << FD << 0;
-    return;
+
+  if (const auto *ExistingAttr = FD->getAttr<WebAssemblyImportNameAttr>()) {
+    if (ExistingAttr->getImportName() == AL.getImportName())
+      return nullptr;
+    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_import) << 1
+      << ExistingAttr->getImportName() << AL.getImportName();
+    Diag(AL.getLoc(), diag::note_previous_attribute);
+    return nullptr;
+  }
+  if (FD->hasBody()) {
+    Diag(AL.getLoc(), diag::warn_import_on_definition) << 1;
+    return nullptr;
   }
+  return ::new (Context) WebAssemblyImportNameAttr(Context, AL,
+                                                   AL.getImportName());
+}
+
+static void
+handleWebAssemblyImportModuleAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  auto *FD = cast<FunctionDecl>(D);
 
   StringRef Str;
   SourceLocation ArgLoc;
   if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &ArgLoc))
     return;
+  if (FD->hasBody()) {
+    S.Diag(AL.getLoc(), diag::warn_import_on_definition) << 0;
+    return;
+  }
 
   FD->addAttr(::new (S.Context)
                   WebAssemblyImportModuleAttr(S.Context, AL, Str));
 }
 
-static void handleWebAssemblyImportNameAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
-  if (!isFunctionOrMethod(D)) {
-    S.Diag(D->getLocation(), diag::warn_attribute_wrong_decl_type)
-        << "'import_name'" << ExpectedFunction;
-    return;
-  }
-
+static void
+handleWebAssemblyImportNameAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   auto *FD = cast<FunctionDecl>(D);
-  if (FD->isThisDeclarationADefinition()) {
-    S.Diag(D->getLocation(), diag::err_alias_is_definition) << FD << 0;
-    return;
-  }
 
   StringRef Str;
   SourceLocation ArgLoc;
   if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &ArgLoc))
     return;
+  if (FD->hasBody()) {
+    S.Diag(AL.getLoc(), diag::warn_import_on_definition) << 1;
+    return;
+  }
 
   FD->addAttr(::new (S.Context) WebAssemblyImportNameAttr(S.Context, AL, Str));
 }

clang/test/AST/ast-dump-wasm-attr-export.c

@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -ast-dump %s | FileCheck --strict-whitespace %s
+
+// Test that functions can be redeclared and they retain their attributes.
+
+__attribute__((export_name("export_red"))) void red(void) {}
+__attribute__((export_name("export_orange"))) void orange(void) {}
+__attribute__((export_name("export_yellow"))) void yellow(void) {}
+
+void red(void);
+void orange(void);
+void yellow(void);
+
+// CHECK: |-FunctionDecl {{.+}} used red 'void (void)'
+// CHECK: | |-CompoundStmt {{.+}}
+// CHECK: | |-WebAssemblyExportNameAttr {{.+}} "export_red"
+// CHECK: | `-UsedAttr {{.+}} Implicit
+// CHECK: |-FunctionDecl {{.+}} used orange 'void (void)'
+// CHECK: | |-CompoundStmt {{.+}}
+// CHECK: | |-WebAssemblyExportNameAttr {{.+}} "export_orange"
+// CHECK: | `-UsedAttr {{.+}} Implicit
+// CHECK: |-FunctionDecl {{.+}} used yellow 'void (void)'
+// CHECK: | |-CompoundStmt {{.+}}
+// CHECK: | |-WebAssemblyExportNameAttr {{.+}} "export_yellow"
+// CHECK: | `-UsedAttr {{.+}} Implicit
+// CHECK: |-FunctionDecl {{.+}} used red 'void (void)'
+// CHECK: | |-UsedAttr {{.+}} Inherited Implicit
+// CHECK: | `-WebAssemblyExportNameAttr {{.+}} Inherited "export_red"
+// CHECK: |-FunctionDecl {{.+}} used orange 'void (void)'
+// CHECK: | |-UsedAttr {{.+}} Inherited Implicit
+// CHECK: | `-WebAssemblyExportNameAttr {{.+}} Inherited "export_orange"
+// CHECK: `-FunctionDecl {{.+}} used yellow 'void (void)'
+// CHECK:   |-UsedAttr {{.+}} Inherited Implicit
+// CHECK:     `-WebAssemblyExportNameAttr {{.+}} Inherited "export_yellow"

clang/test/AST/ast-dump-wasm-attr-import.c

@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -ast-dump %s | FileCheck --strict-whitespace %s
+
+// Test that functions can be redeclared and they retain their attributes.
+
+__attribute__((import_name("import_red"), import_module("mod"))) void red(void);
+__attribute__((import_name("import_orange"), import_module("mod"))) void orange(void);
+__attribute__((import_name("import_yellow"), import_module("mod"))) void yellow(void);
+
+void red(void);
+void orange(void);
+void yellow(void);
+
+void calls(void) {
+    red();
+    orange();
+    yellow();
+}
+
+// CHECK: |-FunctionDecl {{.+}} used red 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} "import_red"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} "mod"
+// CHECK: |-FunctionDecl {{.+}} used orange 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} "import_orange"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} "mod"
+// CHECK: |-FunctionDecl {{.+}} used yellow 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} "import_yellow"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} "mod"
+// CHECK: |-FunctionDecl {{.+}} used red 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} Inherited "import_red"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} Inherited "mod"
+// CHECK: |-FunctionDecl {{.+}} used orange 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} Inherited "import_orange"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} Inherited "mod"
+// CHECK: |-FunctionDecl {{.+}} used yellow 'void (void)'
+// CHECK: | |-WebAssemblyImportNameAttr {{.+}} Inherited "import_yellow"
+// CHECK: | `-WebAssemblyImportModuleAttr {{.+}} Inherited "mod"

clang/test/Sema/attr-wasm.c

@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -fsyntax-only -verify %s
+
+void name_a() __attribute__((import_name)); //expected-error {{'import_name' attribute takes one argument}}
+
+int name_b __attribute__((import_name("foo"))); //expected-error {{'import_name' attribute only applies to functions}}
+
+void name_c() __attribute__((import_name("foo", "bar"))); //expected-error {{'import_name' attribute takes one argument}}
+
+void name_d() __attribute__((import_name("foo", "bar", "qux"))); //expected-error {{'import_name' attribute takes one argument}}
+
+void name_z() __attribute__((import_name("foo"))); //expected-note {{previous attribute is here}}
+
+void name_z() __attribute__((import_name("bar"))); //expected-warning {{import name (bar) does not match the import name (foo) of the previous declaration}}
+
+void module_a() __attribute__((import_module)); //expected-error {{'import_module' attribute takes one argument}}
+
+int module_b __attribute__((import_module("foo"))); //expected-error {{'import_module' attribute only applies to functions}}
+
+void module_c() __attribute__((import_module("foo", "bar"))); //expected-error {{'import_module' attribute takes one argument}}
+
+void module_d() __attribute__((import_module("foo", "bar", "qux"))); //expected-error {{'import_module' attribute takes one argument}}
+
+void module_z() __attribute__((import_module("foo"))); //expected-note {{previous attribute is here}}
+
+void module_z() __attribute__((import_module("bar"))); //expected-warning {{import module (bar) does not match the import module (foo) of the previous declaration}}
+
+void both() __attribute__((import_name("foo"), import_module("bar")));