[PATCH] D124701: [clang] Honor __attribute__((no_builtin("foo"))) on functions

[Stephen Long via Phabricator via cfe-commits]

steplong updated this revision to Diff 428970.
steplong edited the summary of this revision.
steplong added a comment.

- Added `isPredefinedLibFunction()` check
- Added testcase for __attribute__((no_builtin("*")))


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124701/new/

https://reviews.llvm.org/D124701

Files:
  clang/lib/CodeGen/CGExpr.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/CodeGen/no-builtin-2.c


Index: clang/test/CodeGen/no-builtin-2.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/no-builtin-2.c
@@ -0,0 +1,63 @@
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+
+typedef typeof(sizeof(0)) size_t;
+
+void bar(char *s);
+void *memset(void *s, int c, size_t n);
+void *memcpy(void *d, const void *s, size_t n);
+void *memmove(void *d, const void *s, size_t n);
+
+// CHECK: define{{.*}} void @foo1({{.*}}) #[[NO_NOBUILTIN:[0-9]+]]
+// CHECK:   call void @bar
+// CHECK:   call void @llvm.memset
+// CHECK:   call void @llvm.memcpy
+// CHECK:   call void @llvm.memmove
+void foo1(char *s, char *d, size_t n) {
+  bar(s);
+  memset(s, 0, n);
+  memcpy(d, s, n);
+  memmove(d, s, n);
+}
+
+// CHECK: define{{.*}} void @foo2({{.*}}) #[[NOBUILTIN_MEMSET:[0-9]+]]
+// CHECK:   call void @bar
+// CHECK:   {{.*}}call {{.*}} @memset
+// CHECK:   call void @llvm.memcpy
+// CHECK:   call void @llvm.memmove
+void foo2(char *s, char *d, size_t n) __attribute__((no_builtin("memset"))) {
+  bar(s);
+  memset(s, 1, n);
+  memcpy(d, s, n);
+  memmove(d, s, n);
+}
+
+// CHECK: define{{.*}} void @foo3({{.*}}) #[[NOBUILTIN_MEMSET_MEMCPY:[0-9]+]]
+// CHECK:   call void @bar
+// CHECK:   {{.*}}call {{.*}} @memset
+// CHECK:   {{.*}}call {{.*}} @memcpy
+// CHECK:   call void @llvm.memmove
+void foo3(char *s, char *d, size_t n) __attribute__((no_builtin("memset", "memcpy"))) {
+  bar(s);
+  memset(s, 2, n);
+  memcpy(d, s, n);
+  memmove(d, s, n);
+}
+
+// CHECK: define{{.*}} void @foo4({{.*}}) #[[NOBUILTINS:[0-9]+]]
+// CHECK:   call void @bar
+// CHECK:   {{.*}}call {{.*}} @memset
+// CHECK:   {{.*}}call {{.*}} @memcpy
+// CHECK:   {{.*}}call {{.*}} @memmove
+void foo4(char *s, char *d, size_t n) __attribute__((no_builtin("*"))) {
+  bar(s);
+  memset(s, 2, n);
+  memcpy(d, s, n);
+  memmove(s, d, n);
+}
+
+// CHECK-NOT: attributes #[[NO_NOBUILTIN]] = {{{.*}}"no-builtin-memset"{{.*}}}
+// CHECK-NOT: attributes #[[NO_NOBUILTIN]] = {{{.*}}"no-builtin-memcpy"{{.*}}"no-builtin-memset"{{.*}}}
+// CHECK-NOT: attributes #[[NO_NOBUILTIN]] = {{{.*}}"no-builtins"{{.*}}}
+// CHECK:     attributes #[[NOBUILTIN_MEMSET]] = {{{.*}}"no-builtin-memset"{{.*}}}
+// CHECK:     attributes #[[NOBUILTIN_MEMSET_MEMCPY]] = {{{.*}}"no-builtin-memcpy"{{.*}}"no-builtin-memset"{{.*}}}
+// CHECK:     attributes #[[NOBUILTINS]] = {{{.*}}"no-builtins"{{.*}}}
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -1142,7 +1142,8 @@
       if (!S.checkStringLiteralArgumentAttr(AL, I, BuiltinName, &LiteralLoc))
         return;
 
-      if (Builtin::Context::isBuiltinFunc(BuiltinName))
+      bool ParsedAttrIsWildCard = BuiltinName == kWildcard;
+      if (Builtin::Context::isBuiltinFunc(BuiltinName) || ParsedAttrIsWildCard)
         AddBuiltinName(BuiltinName);
       else
         S.Diag(LiteralLoc, diag::warn_attribute_no_builtin_invalid_builtin_name)
Index: clang/lib/CodeGen/CGExpr.cpp
===================================================================
--- clang/lib/CodeGen/CGExpr.cpp
+++ clang/lib/CodeGen/CGExpr.cpp
@@ -5034,7 +5034,16 @@
   const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
 
   if (auto builtinID = FD->getBuiltinID()) {
+    std::string NoBuiltinFD = ("no-builtin-" + FD->getName()).str();
+    std::string NoBuiltins = "no-builtins";
     std::string FDInlineName = (FD->getName() + ".inline").str();
+
+    bool IsPredefinedLibFunction =
+        CGF.getContext().BuiltinInfo.isPredefinedLibFunction(builtinID);
+    bool HasAttributeNoBuiltin =
+        CGF.CurFn->getAttributes().hasFnAttr(NoBuiltinFD) ||
+        CGF.CurFn->getAttributes().hasFnAttr(NoBuiltins);
+
     // When directing calling an inline builtin, call it through it's mangled
     // name to make it clear it's not the actual builtin.
     if (CGF.CurFn->getName() != FDInlineName &&
@@ -5054,8 +5063,11 @@
 
     // Replaceable builtins provide their own implementation of a builtin. If we
     // are in an inline builtin implementation, avoid trivial infinite
-    // recursion.
-    else
+    // recursion. Honor __attribute__((no_builtin("foo"))) or
+    // __attribute((no_builtin("*"))) on the current function unless foo is
+    // not a predefined library function which means we must generate the
+    // builtin no matter what.
+    else if (!IsPredefinedLibFunction || !HasAttributeNoBuiltin)
       return CGCallee::forBuiltin(builtinID, FD);
   }
 

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