[Clang][CodeGen] Implement code generation for __builtin_infer_alloc_token()

clang/docs/AllocToken.rst

@@ -49,6 +49,39 @@ change or removal. These may (experimentally) be selected with ``-Xclang
 * ``increment``: This mode assigns a simple, incrementally increasing token ID
   to each allocation site.
 
+The following command-line options affect generated token IDs:
+
+* ``-falloc-token-max=<N>``
+    Configures the maximum number of tokens. No max by default (tokens bounded
+    by ``SIZE_MAX``).
+
+Querying Token IDs with ``__builtin_infer_alloc_token``
+=======================================================
+
+For use cases where the token ID must be known at compile time, Clang provides
+a builtin function:
+
+.. code-block:: c
+
+    size_t __builtin_infer_alloc_token(<args>, ...);
+
+This builtin returns the token ID inferred from its argument expressions, which
+mirror arguments normally passed to any allocation function. The argument
+expressions are **unevaluated**, so it can be used with expressions that would
+have side effects without any runtime impact.
+
+For example, it can be used as follows:
+
+.. code-block:: c
+
+    struct MyType { ... };
+    void *__partition_alloc(size_t size, size_t partition);
+    #define partition_alloc(...) __partition_alloc(__VA_ARGS__, __builtin_infer_alloc_token(__VA_ARGS__))
+
+    void foo(void) {
+        MyType *x = partition_alloc(sizeof(*x));
+    }
+
 Allocation Token Instrumentation
 ================================
 
@@ -70,16 +103,6 @@ example:
     // Instrumented:
     ptr = __alloc_token_malloc(size, <token id>);
 
-The following command-line options affect generated token IDs:
-
-* ``-falloc-token-max=<N>``
-    Configures the maximum number of tokens. No max by default (tokens bounded
-    by ``SIZE_MAX``).
-
-    .. code-block:: console
-
-        % clang++ -fsanitize=alloc-token -falloc-token-max=512 example.cc
-
 Runtime Interface
 -----------------
 

clang/docs/ReleaseNotes.rst

@@ -268,6 +268,9 @@ Non-comprehensive list of changes in this release
   allocator-level heap organization strategies. A feature to instrument all
   allocation functions with a token ID can be enabled via the
   ``-fsanitize=alloc-token`` flag.
+- A builtin ``__builtin_infer_alloc_token(<args>, ...)`` is provided to allow
+  compile-time querying of allocation token IDs, where the builtin arguments
+  mirror those normally passed to an allocation function.
 
 New Compiler Flags
 ------------------

clang/lib/CodeGen/BackendUtil.cpp

@@ -803,16 +803,6 @@ static void addSanitizers(const Triple &TargetTriple,
       MPM.addPass(DataFlowSanitizerPass(LangOpts.NoSanitizeFiles,
                                         PB.getVirtualFileSystemPtr()));
     }
-
-    if (LangOpts.Sanitize.has(SanitizerKind::AllocToken)) {
-      if (Level == OptimizationLevel::O0) {
-        // The default pass builder only infers libcall function attrs when
-        // optimizing, so we insert it here because we need it for accurate
-        // memory allocation function detection.
-        MPM.addPass(InferFunctionAttrsPass());
-      }
-      MPM.addPass(AllocTokenPass(getAllocTokenOptions(LangOpts, CodeGenOpts)));
-    }
   };
   if (ClSanitizeOnOptimizerEarlyEP) {
     PB.registerOptimizerEarlyEPCallback(
@@ -855,6 +845,23 @@ static void addSanitizers(const Triple &TargetTriple,
   }
 }
 
+static void addAllocTokenPass(const Triple &TargetTriple,
+                              const CodeGenOptions &CodeGenOpts,
+                              const LangOptions &LangOpts, PassBuilder &PB) {
+  PB.registerOptimizerLastEPCallback([&](ModulePassManager &MPM,
+                                         OptimizationLevel Level,
+                                         ThinOrFullLTOPhase) {
+    if (Level == OptimizationLevel::O0 &&
+        LangOpts.Sanitize.has(SanitizerKind::AllocToken)) {
+      // The default pass builder only infers libcall function attrs when
+      // optimizing, so we insert it here because we need it for accurate
+      // memory allocation function detection with -fsanitize=alloc-token.
+      MPM.addPass(InferFunctionAttrsPass());
+    }
+    MPM.addPass(AllocTokenPass(getAllocTokenOptions(LangOpts, CodeGenOpts)));
+  });
+}
+
 void EmitAssemblyHelper::RunOptimizationPipeline(
     BackendAction Action, std::unique_ptr<raw_pwrite_stream> &OS,
     std::unique_ptr<llvm::ToolOutputFile> &ThinLinkOS, BackendConsumer *BC) {
@@ -1109,6 +1116,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
     if (!IsThinLTOPostLink) {
       addSanitizers(TargetTriple, CodeGenOpts, LangOpts, PB);
       addKCFIPass(TargetTriple, LangOpts, PB);
+      addAllocTokenPass(TargetTriple, CodeGenOpts, LangOpts, PB);
     }
 
     if (std::optional<GCOVOptions> Options =

clang/lib/CodeGen/CGBuiltin.cpp

@@ -4525,6 +4525,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(AI);
   }
 
+  case Builtin::BI__builtin_infer_alloc_token: {
+    llvm::MDNode *MDN = buildAllocToken(E);
+    llvm::Value *MDV = MetadataAsValue::get(getLLVMContext(), MDN);
+    llvm::Function *F =
+        CGM.getIntrinsic(llvm::Intrinsic::alloc_token_id, {IntPtrTy});
+    llvm::CallBase *TokenID = Builder.CreateCall(F, MDV);
+    return RValue::get(TokenID);
+  }
+
   case Builtin::BIbzero:
   case Builtin::BI__builtin_bzero: {
     Address Dest = EmitPointerWithAlignment(E->getArg(0));

clang/test/CodeGen/lto-newpm-pipeline.c

@@ -32,10 +32,12 @@
 // CHECK-FULL-O0-NEXT: Running pass: AlwaysInlinerPass
 // CHECK-FULL-O0-NEXT: Running analysis: ProfileSummaryAnalysis
 // CHECK-FULL-O0-NEXT: Running pass: CoroConditionalWrapper
+// CHECK-FULL-O0-NEXT: Running pass: AllocTokenPass
+// CHECK-FULL-O0-NEXT: Running analysis: OptimizationRemarkEmitterAnalysis
+// CHECK-FULL-O0-NEXT: Running analysis: TargetLibraryAnalysis
 // CHECK-FULL-O0-NEXT: Running pass: CanonicalizeAliasesPass
 // CHECK-FULL-O0-NEXT: Running pass: NameAnonGlobalPass
 // CHECK-FULL-O0-NEXT: Running pass: AnnotationRemarksPass
-// CHECK-FULL-O0-NEXT: Running analysis: TargetLibraryAnalysis
 // CHECK-FULL-O0-NEXT: Running pass: VerifierPass
 // CHECK-FULL-O0-NEXT: Running pass: BitcodeWriterPass
 
@@ -46,10 +48,12 @@
 // CHECK-THIN-O0-NEXT: Running pass: AlwaysInlinerPass
 // CHECK-THIN-O0-NEXT: Running analysis: ProfileSummaryAnalysis
 // CHECK-THIN-O0-NEXT: Running pass: CoroConditionalWrapper
+// CHECK-THIN-O0-NEXT: Running pass: AllocTokenPass
+// CHECK-THIN-O0-NEXT: Running analysis: OptimizationRemarkEmitterAnalysis
+// CHECK-THIN-O0-NEXT: Running analysis: TargetLibraryAnalysis
 // CHECK-THIN-O0-NEXT: Running pass: CanonicalizeAliasesPass
 // CHECK-THIN-O0-NEXT: Running pass: NameAnonGlobalPass
 // CHECK-THIN-O0-NEXT: Running pass: AnnotationRemarksPass
-// CHECK-THIN-O0-NEXT: Running analysis: TargetLibraryAnalysis
 // CHECK-THIN-O0-NEXT: Running pass: VerifierPass
 // CHECK-THIN-O0-NEXT: Running pass: ThinLTOBitcodeWriterPass
 

clang/test/CodeGenCXX/alloc-token-builtin.cpp

@@ -0,0 +1,77 @@
+// To test IR generation of the builtin without evaluating the LLVM intrinsic,
+// we set the mode to a stateful mode, which prohibits constant evaluation.
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -Werror -std=c++20 -emit-llvm -falloc-token-mode=random -disable-llvm-passes %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-CODEGEN
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -Werror -std=c++20 -emit-llvm -falloc-token-max=2 %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-LOWER
+
+extern "C" void *my_malloc(unsigned long, unsigned long);
+
+struct NoPtr {
+  int x;
+  long y;
+};
+
+struct WithPtr {
+  int a;
+  char *buf;
+};
+
+int unevaluated_fn();
+
+// CHECK-LABEL: @_Z16test_builtin_intv(
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_INT:[0-9]+]])
+// CHECK-LOWER: ret i64 0
+unsigned long test_builtin_int() {
+  return __builtin_infer_alloc_token(sizeof(1));
+}
+
+// CHECK-LABEL: @_Z16test_builtin_ptrv(
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_PTR:[0-9]+]])
+// CHECK-LOWER: ret i64 1
+unsigned long test_builtin_ptr() {
+  return __builtin_infer_alloc_token(sizeof(int *));
+}
+
+// CHECK-LABEL: @_Z25test_builtin_struct_noptrv(
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_NOPTR:[0-9]+]])
+// CHECK-LOWER: ret i64 0
+unsigned long test_builtin_struct_noptr() {
+  return __builtin_infer_alloc_token(sizeof(NoPtr));
+}
+
+// CHECK-LABEL: @_Z25test_builtin_struct_w_ptrv(
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_WITHPTR:[0-9]+]])
+// CHECK-LOWER: ret i64 1
+unsigned long test_builtin_struct_w_ptr() {
+  return __builtin_infer_alloc_token(sizeof(WithPtr), 123);
+}
+
+// CHECK-LABEL: @_Z24test_builtin_unevaluatedv(
+// CHECK-NOT: call{{.*}}unevaluated_fn
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_INT:[0-9]+]])
+// CHECK-LOWER: ret i64 0
+unsigned long test_builtin_unevaluated() {
+	return __builtin_infer_alloc_token(sizeof(int) * unevaluated_fn());
+}
+
+// CHECK-LABEL: @_Z36test_builtin_unsequenced_unevaluatedi(
+// CHECK:     add nsw
+// CHECK-NOT: add nsw
+// CHECK-CODEGEN: %[[REG:[0-9]+]] = call i64 @llvm.alloc.token.id.i64(metadata ![[META_UNKNOWN:[0-9]+]])
+// CHECK-CODEGEN: call{{.*}}@my_malloc({{.*}}, i64 noundef %[[REG]])
+// CHECK-LOWER: call{{.*}}@my_malloc({{.*}}, i64 noundef 0)
+void test_builtin_unsequenced_unevaluated(int x) {
+  my_malloc(++x, __builtin_infer_alloc_token(++x));
+}
+
+// CHECK-LABEL: @_Z20test_builtin_unknownv(
+// CHECK-CODEGEN: call i64 @llvm.alloc.token.id.i64(metadata ![[META_UNKNOWN:[0-9]+]])
+// CHECK-LOWER: ret i64 0
+unsigned long test_builtin_unknown() {
+  return __builtin_infer_alloc_token(4096);
+}
+
+// CHECK-CODEGEN: ![[META_INT]] = !{!"int", i1 false}
+// CHECK-CODEGEN: ![[META_PTR]] = !{!"int *", i1 true}
+// CHECK-CODEGEN: ![[META_NOPTR]] = !{!"NoPtr", i1 false}
+// CHECK-CODEGEN: ![[META_WITHPTR]] = !{!"WithPtr", i1 true}
+// CHECK-CODEGEN: ![[META_UNKNOWN]] = !{}