[llvm-branch-commits] [clang] 241275a - Revert "[Clang] Propagate guaranteed alignment for malloc and others"
James Y Knight via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Tue Feb 8 15:00:33 PST 2022
Author: James Y Knight
Date: 2022-02-08T17:16:19-05:00
New Revision: 241275a01ed88cd59d503449a8c74a3b7cfedbb2
URL: https://github.com/llvm/llvm-project/commit/241275a01ed88cd59d503449a8c74a3b7cfedbb2
DIFF: https://github.com/llvm/llvm-project/commit/241275a01ed88cd59d503449a8c74a3b7cfedbb2.diff
LOG: Revert "[Clang] Propagate guaranteed alignment for malloc and others"
The above change assumed that malloc (and friends) would always
allocate memory to getNewAlign(), even for allocations which have a
smaller size. This is not actually required by spec (a 1-byte
allocation may validly have 1-byte alignment).
Some real-world malloc implementations do not provide this guarantee,
and thus this optimization is breaking programs.
Fixes #53540
This reverts commit c2297544c04764237cedc523083c7be2fb3833d4.
Differential Revision: https://reviews.llvm.org/D118804
(cherry picked from commit 9545976ff160e19805a84a06a7e59d446f9994d9)
Added:
Modified:
clang/include/clang/Basic/TargetInfo.h
clang/lib/Sema/SemaDecl.cpp
clang/test/CodeGen/alloc-fns-alignment.c
Removed:
################################################################################
diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index a49342a34f3e8..e7db877f4e2bc 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -644,8 +644,8 @@ class TargetInfo : public virtual TransferrableTargetInfo,
}
/// Return the largest alignment for which a suitably-sized allocation with
- /// '::operator new(size_t)' or 'malloc' is guaranteed to produce a
- /// correctly-aligned pointer.
+ /// '::operator new(size_t)' is guaranteed to produce a correctly-aligned
+ /// pointer.
unsigned getNewAlign() const {
return NewAlign ? NewAlign : std::max(LongDoubleAlign, LongLongAlign);
}
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index cbd9df4d6a7b7..bcadf4139046c 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -15319,24 +15319,7 @@ void Sema::AddKnownFunctionAttributes(FunctionDecl *FD) {
if (!FD->hasAttr<AllocAlignAttr>())
FD->addAttr(AllocAlignAttr::CreateImplicit(Context, ParamIdx(1, FD),
FD->getLocation()));
- LLVM_FALLTHROUGH;
- case Builtin::BIcalloc:
- case Builtin::BImalloc:
- case Builtin::BImemalign:
- case Builtin::BIrealloc:
- case Builtin::BIstrdup:
- case Builtin::BIstrndup: {
- if (!FD->hasAttr<AssumeAlignedAttr>()) {
- unsigned NewAlign = Context.getTargetInfo().getNewAlign() /
- Context.getTargetInfo().getCharWidth();
- IntegerLiteral *Alignment = IntegerLiteral::Create(
- Context, Context.MakeIntValue(NewAlign, Context.UnsignedIntTy),
- Context.UnsignedIntTy, FD->getLocation());
- FD->addAttr(AssumeAlignedAttr::CreateImplicit(
- Context, Alignment, /*Offset=*/nullptr, FD->getLocation()));
- }
break;
- }
default:
break;
}
diff --git a/clang/test/CodeGen/alloc-fns-alignment.c b/clang/test/CodeGen/alloc-fns-alignment.c
index 8ab0610accf03..31dc9bb2d759d 100644
--- a/clang/test/CodeGen/alloc-fns-alignment.c
+++ b/clang/test/CodeGen/alloc-fns-alignment.c
@@ -1,11 +1,9 @@
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm < %s | FileCheck %s --check-prefix=ALIGN16
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm < %s | FileCheck %s --check-prefix=ALIGN16
-// RUN: %clang_cc1 -triple i386-apple-darwin -emit-llvm < %s | FileCheck %s --check-prefix=ALIGN16
-// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -emit-llvm < %s | FileCheck %s --check-prefix=ALIGN8
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fno-builtin-malloc -emit-llvm < %s | FileCheck %s --check-prefix=NOBUILTIN-MALLOC
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fno-builtin-calloc -emit-llvm < %s | FileCheck %s --check-prefix=NOBUILTIN-CALLOC
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fno-builtin-realloc -emit-llvm < %s | FileCheck %s --check-prefix=NOBUILTIN-REALLOC
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fno-builtin-aligned_alloc -emit-llvm < %s | FileCheck %s --check-prefix=NOBUILTIN-ALIGNED_ALLOC
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm < %s | FileCheck %s
+
+// Note: this test originally asserted that malloc/calloc/realloc got alignment
+// attributes on their return pointer. However, that was reverted in
+// https://reviews.llvm.org/D118804 and it now asserts that they do _NOT_ get
+// align attributes.
typedef __SIZE_TYPE__ size_t;
@@ -39,43 +37,29 @@ void *aligned_alloc_large_constant_test(size_t n) {
}
// CHECK-LABEL: @malloc_test
-// ALIGN16: align 16 i8* @malloc
-
-// CHECK-LABEL: @calloc_test
-// ALIGN16: align 16 i8* @calloc
-
-// CHECK-LABEL: @realloc_test
-// ALIGN16: align 16 i8* @realloc
-
-// CHECK-LABEL: @aligned_alloc_variable_test
-// ALIGN16: %[[ALLOCATED:.*]] = call align 16 i8* @aligned_alloc({{i32|i64}} noundef %[[ALIGN:.*]], {{i32|i64}} noundef %[[NBYTES:.*]])
-// ALIGN16-NEXT: call void @llvm.assume(i1 true) [ "align"(i8* %[[ALLOCATED]], {{i32|i64}} %[[ALIGN]]) ]
+// CHECK: call i8* @malloc
-// CHECK-LABEL: @aligned_alloc_constant_test
-// ALIGN16: align 16 i8* @aligned_alloc
-
-// CHECK-LABEL: @aligned_alloc_large_constant_test
-// ALIGN16: align 4096 i8* @aligned_alloc
-
-// CHECK-LABEL: @malloc_test
-// ALIGN8: align 8 i8* @malloc
+// CHECK: declare i8* @malloc
// CHECK-LABEL: @calloc_test
-// ALIGN8: align 8 i8* @calloc
+// CHECK: call i8* @calloc
+
+// CHECK: declare i8* @calloc
// CHECK-LABEL: @realloc_test
-// ALIGN8: align 8 i8* @realloc
+// CHECK: call i8* @realloc
+
+// CHECK: declare i8* @realloc
// CHECK-LABEL: @aligned_alloc_variable_test
-// ALIGN8: align 8 i8* @aligned_alloc
+// CHECK: %[[ALLOCATED:.*]] = call i8* @aligned_alloc({{i32|i64}} noundef %[[ALIGN:.*]], {{i32|i64}} noundef %[[NBYTES:.*]])
+// CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(i8* %[[ALLOCATED]], {{i32|i64}} %[[ALIGN]]) ]
+
+// CHECK: declare i8* @aligned_alloc
// CHECK-LABEL: @aligned_alloc_constant_test
-// ALIGN8: align 8 i8* @aligned_alloc
+// CHECK: call align 8 i8* @aligned_alloc
// CHECK-LABEL: @aligned_alloc_large_constant_test
-// ALIGN8: align 4096 i8* @aligned_alloc
+// CHECK: call align 4096 i8* @aligned_alloc
-// NOBUILTIN-MALLOC: declare i8* @malloc
-// NOBUILTIN-CALLOC: declare i8* @calloc
-// NOBUILTIN-REALLOC: declare i8* @realloc
-// NOBUILTIN-ALIGNED_ALLOC: declare i8* @aligned_alloc
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