In LLVM IR, `AlignmentBitfieldElementT` is 5-bit wide
But that means that the maximal alignment exponent is `(1<<5)-2`,
which is `30`, not `29`. And indeed, alignment of `1073741824`
roundtrips IR serialization-deserialization.
While this doesn't seem all that important, this doubles
the maximal supported alignment from 512MiB to 1GiB,
and there's actually one noticeable use-case for that;
On X86, the huge pages can have sizes of 2MiB and 1GiB (!).
So while this doesn't add support for truly huge alignments,
which i think we can easily-ish do if wanted, i think this adds
zero-cost support for a not-trivially-dismissable case.
I don't believe we need any upgrade infrastructure,
and since we don't explicitly record the IR version,
we don't need to bump one either.
As @craig.topper speculates in D108661#2963519,
this might be an artificial limit imposed by the original implementation
of the `getAlignment()` functions.
Differential Revision: https://reviews.llvm.org/D108661
There is llvm::Value::MaximumAlignment, which is numerically
equivalent to these constants, but we can't use it directly
because we can't include llvm IR headers in clang Sema.
So instead, copy-paste the constant, and fixup the places to use it.
This was initially reviewed in https://reviews.llvm.org/D72998
Sema allows max values up to 2**28, use unsigned instead of unsiged
short to hold values that large.
Differential Revision: http://reviews.llvm.org/D17248
Patch by Don Hinton!
llvm-svn: 262466
When instantiating an array that has an alignment attribute on it, we
were looking through the array type and only considering the element
type for the resulting alignment. We need to make sure we take the
array's requirements into account too.
llvm-svn: 206317
When calculating the preferred alignment of a type, consider if a alignment
attribute came from a typedef declaration. If one did, do not naturally align
the type.
Patch by Stephan Tolksdorf, with a little tweaking and an additional testcase by me.
llvm-svn: 202088
__attribute__((aligned)). Fixes <rdar://problem/11435441>, a
regression I introduced in r156003. This is the narrow fix; a more
comprehensive fix is coming.
llvm-svn: 156657
unless it's a non-packed field, in which case it can only increase the
alignment. [[align]] effectively works the same way for well-formed code
(because it's ill-formed for [[align]] to decrease alignment ever).
Fixes rdar://problem/8335865
llvm-svn: 116070
- This is designed to make it obvious that %clang_cc1 is a "test variable"
which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
can be useful to redefine what gets run as 'clang -cc1' (for example, to set
a default target).
llvm-svn: 91446
"aligned" attribute. Previously, we were skipping over these
attributes when we jumped directly to the canonical type. Now,
ASTContext::getTypeInfo walks through typedefs and other
"non-canonical" types manually, looking for "aligned" attributes on
typedefs.
As part of this change, I moved the GNU-specific logic (such as
determining the alignment of void or of a function pointer) out of the
expression evaluator and into ASTContext::getTypeInfo.
llvm-svn: 70497
Arthur Eubanks