jyknight created this revision.
jyknight added reviewers: aaron.ballman, rjmccall, jdoerfert, xbolva00.
jyknight requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
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
<https://reviews.llvm.org/rGc2297544c04764237cedc523083c7be2fb3833d4>.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D118804
Files:
clang/include/clang/Basic/TargetInfo.h
clang/test/CodeGen/alloc-fns-alignment.c
Index: clang/test/CodeGen/alloc-fns-alignment.c
===================================================================
--- clang/test/CodeGen/alloc-fns-alignment.c
+++ /dev/null
@@ -1,81 +0,0 @@
-// 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
-
-typedef __SIZE_TYPE__ size_t;
-
-void *malloc(size_t);
-void *calloc(size_t, size_t);
-void *realloc(void *, size_t);
-void *aligned_alloc(size_t, size_t);
-
-void *malloc_test(size_t n) {
- return malloc(n);
-}
-
-void *calloc_test(size_t n) {
- return calloc(1, n);
-}
-
-void *realloc_test(void *p, size_t n) {
- return realloc(p, n);
-}
-
-void *aligned_alloc_variable_test(size_t n, size_t a) {
- return aligned_alloc(a, n);
-}
-
-void *aligned_alloc_constant_test(size_t n) {
- return aligned_alloc(8, n);
-}
-
-void *aligned_alloc_large_constant_test(size_t n) {
- return aligned_alloc(4096, 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-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-LABEL: @calloc_test
-// ALIGN8: align 8 i8* @calloc
-
-// CHECK-LABEL: @realloc_test
-// ALIGN8: align 8 i8* @realloc
-
-// CHECK-LABEL: @aligned_alloc_variable_test
-// ALIGN8: align 8 i8* @aligned_alloc
-
-// CHECK-LABEL: @aligned_alloc_constant_test
-// ALIGN8: align 8 i8* @aligned_alloc
-
-// CHECK-LABEL: @aligned_alloc_large_constant_test
-// ALIGN8: 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
Index: clang/include/clang/Basic/TargetInfo.h
===================================================================
--- clang/include/clang/Basic/TargetInfo.h
+++ clang/include/clang/Basic/TargetInfo.h
@@ -646,8 +646,8 @@
}
/// 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);
}
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