https://github.com/dpaoliello updated
https://github.com/llvm/llvm-project/pull/116847
>From d97c75c91d5b4a8b6c490ce125f3c7cf0f62b234 Mon Sep 17 00:00:00 2001
From: "Daniel Paoliello (HE/HIM)" <dan...@microsoft.com>
Date: Tue, 19 Nov 2024 09:34:51 -0800
Subject: [PATCH] [clang] Add support for __declspec(no_init_all)
---
clang/include/clang/Basic/Attr.td | 7 +++
clang/include/clang/Basic/AttrDocs.td | 12 ++++
clang/lib/CodeGen/CGDecl.cpp | 22 ++++----
clang/test/CodeGenCXX/auto-var-init-attr.cpp | 59 ++++++++++++++++++++
4 files changed, 90 insertions(+), 10 deletions(-)
create mode 100644 clang/test/CodeGenCXX/auto-var-init-attr.cpp
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index 6035a563d5fce7..634253d0032560 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -4888,3 +4888,10 @@ def ClspvLibclcBuiltin: InheritableAttr {
let Documentation = [ClspvLibclcBuiltinDoc];
let SimpleHandler = 1;
}
+
+def NoTrivialAutoVarInit: InheritableAttr {
+ let Spellings = [Declspec<"no_init_all">];
+ let Subjects = SubjectList<[Function, Tag]>;
+ let Documentation = [NoTrivialAutoVarInitDocs];
+ let SimpleHandler = 1;
+}
diff --git a/clang/include/clang/Basic/AttrDocs.td
b/clang/include/clang/Basic/AttrDocs.td
index 2fdceca163ee63..8d727ac7bb4210 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -8719,6 +8719,18 @@ Attribute used by `clspv`_ (OpenCL-C to Vulkan SPIR-V
compiler) to identify func
}];
}
+def NoTrivialAutoVarInitDocs : Documentation {
+ let Category = DocCatDecl;
+ let Content = [{
+The ``__declspec(no_init_all)`` attribute disables the automatic
initialization that the
+`-ftrivial-auto-var-init`_ flag would have applied to locals in a marked
function, or instances of
+a marked type. Note that this attribute has no effect for locals that are
automatically initialized
+without the `-ftrivial-auto-var-init`_ flag.
+
+.. _`-ftrivial-auto-var-init`:
https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-ftrivial-auto-var-init
+}];
+}
+
def DocCatNonBlockingNonAllocating : DocumentationCategory<"Performance
Constraint Attributes"> {
let Content = [{
The ``nonblocking``, ``blocking``, ``nonallocating`` and ``allocating``
attributes can be attached
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 6e9d28cea28e79..47b21bc9f63f04 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -1899,13 +1899,16 @@ void CodeGenFunction::EmitAutoVarInit(const
AutoVarEmission &emission) {
const Address Loc =
locIsByrefHeader ? emission.getObjectAddress(*this) : emission.Addr;
+ auto hasNoTrivialAutoVarInitAttr = [&](const Decl *D) {
+ return D && D->hasAttr<NoTrivialAutoVarInitAttr>();
+ };
// Note: constexpr already initializes everything correctly.
LangOptions::TrivialAutoVarInitKind trivialAutoVarInit =
- (D.isConstexpr()
+ ((D.isConstexpr() || D.getAttr<UninitializedAttr>() ||
+ hasNoTrivialAutoVarInitAttr(type->getAsTagDecl()) ||
+ hasNoTrivialAutoVarInitAttr(CurFuncDecl))
? LangOptions::TrivialAutoVarInitKind::Uninitialized
- : (D.getAttr<UninitializedAttr>()
- ? LangOptions::TrivialAutoVarInitKind::Uninitialized
- : getContext().getLangOpts().getTrivialAutoVarInit()));
+ : getContext().getLangOpts().getTrivialAutoVarInit());
auto initializeWhatIsTechnicallyUninitialized = [&](Address Loc) {
if (trivialAutoVarInit ==
@@ -1944,13 +1947,13 @@ void CodeGenFunction::EmitAutoVarInit(const
AutoVarEmission &emission) {
replaceUndef(CGM, isPattern, constant));
}
- if (constant && D.getType()->isBitIntType() &&
- CGM.getTypes().typeRequiresSplitIntoByteArray(D.getType())) {
+ if (constant && type->isBitIntType() &&
+ CGM.getTypes().typeRequiresSplitIntoByteArray(type)) {
// Constants for long _BitInt types are split into individual bytes.
// Try to fold these back into an integer constant so it can be stored
// properly.
- llvm::Type *LoadType = CGM.getTypes().convertTypeForLoadStore(
- D.getType(), constant->getType());
+ llvm::Type *LoadType =
+ CGM.getTypes().convertTypeForLoadStore(type, constant->getType());
constant = llvm::ConstantFoldLoadFromConst(
constant, LoadType, llvm::APInt::getZero(32), CGM.getDataLayout());
}
@@ -1967,8 +1970,7 @@ void CodeGenFunction::EmitAutoVarInit(const
AutoVarEmission &emission) {
// It may be that the Init expression uses other uninitialized memory,
// but auto-var-init here would not help, as auto-init would get
// overwritten by Init.
- if (!D.getType()->isScalarType() || capturedByInit ||
- isAccessedBy(D, Init)) {
+ if (!type->isScalarType() || capturedByInit || isAccessedBy(D, Init)) {
initializeWhatIsTechnicallyUninitialized(Loc);
}
}
diff --git a/clang/test/CodeGenCXX/auto-var-init-attr.cpp
b/clang/test/CodeGenCXX/auto-var-init-attr.cpp
new file mode 100644
index 00000000000000..5481c6e8613c56
--- /dev/null
+++ b/clang/test/CodeGenCXX/auto-var-init-attr.cpp
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 -std=c++14 -triple x86_64-unknown-unknown -fblocks
-fdeclspec -ftrivial-auto-var-init=zero %s -emit-llvm -o - | FileCheck %s
+
+struct S { char c; };
+class C { char c; };
+enum class E { ZERO };
+union U { char c; int i; };
+
+struct __declspec(no_init_all) NoInitS { char c; };
+class __declspec(no_init_all) NoInitC { char c; };
+enum class __declspec(no_init_all) NoInitE { ZERO };
+union __declspec(no_init_all) NoInitU { char c; int i; };
+
+extern "C" {
+ void test_no_attr() {
+ // CHECK-LABEL: @test_no_attr()
+ // CHECK-NEXT: entry:
+ // CHECK-NEXT: %s = alloca %struct.S, align 1
+ // CHECK-NEXT: %c = alloca %class.C, align 1
+ // CHECK-NEXT: %e = alloca i32, align 4
+ // CHECK-NEXT: %u = alloca %union.U, align 4
+ // CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 1 %s, i8 0, i64 1,
i1 false)
+ // CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 1 %c, i8 0, i64 1,
i1 false)
+ // CHECK-NEXT: store i32 0, ptr %e, align 4
+ // CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4 %u, i8 0, i64 4,
i1 false)
+ // CHECK-NEXT ret void
+ S s;
+ C c;
+ E e;
+ U u;
+ }
+
+ void __declspec(no_init_all) test_attr_on_function() {
+ // CHECK-LABEL: @test_attr_on_function()
+ // CHECK-NEXT: entry:
+ // CHECK-NEXT: %s = alloca %struct.S, align 1
+ // CHECK-NEXT: %c = alloca %class.C, align 1
+ // CHECK-NEXT: %e = alloca i32, align 4
+ // CHECK-NEXT: %u = alloca %union.U, align 4
+ // CHECK-NEXT: ret void
+ S s;
+ C c;
+ E e;
+ U u;
+ }
+
+ void test_attr_on_decl() {
+ // CHECK-LABEL: @test_attr_on_decl()
+ // CHECK-NEXT: entry:
+ // CHECK-NEXT: %s = alloca %struct.NoInitS, align 1
+ // CHECK-NEXT: %c = alloca %class.NoInitC, align 1
+ // CHECK-NEXT: %e = alloca i32, align 4
+ // CHECK-NEXT: %u = alloca %union.NoInitU, align 4
+ // CHECK-NEXT: ret void
+ NoInitS s;
+ NoInitC c;
+ NoInitE e;
+ NoInitU u;
+ }
+}
\ No newline at end of file
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