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[Sema] Try 2: Sanity-check alignment requested via `__attribute__((assume_aligned(imm)))` 

Summary:
For `__builtin_assume_aligned()`, we do validate that the alignment
is not greater than `536870912` (D68824), but we don't do that for
`__attribute__((assume_aligned(N)))` attribute.
I suspect we should.

This was initially committed in a4cfb15d15
but reverted in 210f0882c9 due to
suspicious bot failures.

Reviewers: erichkeane, aaron.ballman, hfinkel, rsmith, jdoerfert

Reviewed By: erichkeane

Subscribers: cfe-commits, llvm-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D72994
This commit is contained in:
Roman Lebedev 2020-01-23 22:48:57 +03:00
parent 5cee34013c
commit 0a002f679b
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2 changed files with 7 additions and 0 deletions
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6
clang/lib/Sema/SemaDeclAttr.cpp
View File

@ -1625,6 +1625,12 @@ void Sema::AddAssumeAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
<< E->getSourceRange();
return;
}
// Alignment calculations can wrap around if it's greater than 2**29.
unsigned MaximumAlignment = 536870912;
if (I > MaximumAlignment)
Diag(CI.getLoc(), diag::warn_assume_aligned_too_great)
<< CI.getRange() << MaximumAlignment;
}
if (OE) {

1
clang/test/Sema/builtin-assume-aligned.c
View File

@ -46,6 +46,7 @@ int test8(int *a, int j) {
void test_void_assume_aligned(void) __attribute__((assume_aligned(32))); // expected-warning {{'assume_aligned' attribute only applies to return values that are pointers}}
int test_int_assume_aligned(void) __attribute__((assume_aligned(16))); // expected-warning {{'assume_aligned' attribute only applies to return values that are pointers}}
void *test_ptr_assume_aligned(void) __attribute__((assume_aligned(64))); // no-warning
void *test_ptr_assume_aligned(void) __attribute__((assume_aligned(1073741824))); // expected-warning {{requested alignment must be 536870912 bytes or smaller; maximum alignment assumed}}
int j __attribute__((assume_aligned(8))); // expected-warning {{'assume_aligned' attribute only applies to Objective-C methods and functions}}
void *test_no_fn_proto() __attribute__((assume_aligned(32))); // no-warning