The grammar for LLVM IR is not well specified in any document but seems
to obey the following rules:
- Attributes which have parenthesized arguments are never preceded by
commas. This form of attribute is the only one which ever has
optional arguments. However, not all of these attributes support
optional arguments: 'thread_local' supports an optional argument but
'addrspace' does not. Interestingly, 'addrspace' is documented as
being a "qualifier". What constitutes a qualifier? I cannot find a
definition.
- Some attributes use a space between the keyword and the value.
Examples of this form are 'align' and 'section'. These are always
preceded by a comma.
- Otherwise, the attribute has no argument. These attributes do not
have a preceding comma.
Sometimes an attribute goes before the instruction, between the
instruction and it's type, or after it's type. 'atomicrmw' has
'volatile' between the instruction and the type while 'call' has 'tail'
preceding the instruction.
With all this in mind, it seems most consistent for 'inalloca' on an
'inalloca' instruction to occur before between the instruction and the
type. Unlike the current formulation, there would be no preceding
comma. The combination 'alloca inalloca' doesn't look particularly
appetizing, perhaps a better spelling of 'inalloca' is down the road.
llvm-svn: 203376
Summary:
The only current use of this flag is to mark the alloca as dynamic, even
if its in the entry block. The stack adjustment for the alloca can
never be folded into the prologue because the call may clear it and it
has to be allocated at the top of the stack.
Reviewers: majnemer
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2571
llvm-svn: 199525
This makes things a lot easier, because we can now talk about the
"argument allocation", which allocates all the memory for the call in
one shot.
The only functional change is to the verifier for a feature that hasn't
shipped yet.
llvm-svn: 199434
The inalloca attribute is designed to support passing C++ objects by
value in the Microsoft C++ ABI. It behaves the same as byval, except
that it always implies that the argument is in memory and that the bytes
are never copied. This attribute allows the caller to take the address
of an outgoing argument's memory and execute arbitrary code to store
into it.
This patch adds basic IR support, docs, and verification. It does not
attempt to implement any lowering or fix any possibly broken transforms.
When this patch lands, a complete description of this feature should
appear at http://llvm.org/docs/InAlloca.html .
Differential Revision: http://llvm-reviews.chandlerc.com/D2173
llvm-svn: 197645
David Majnemer