ICallingConvention

The flag indicates that all composite arguments (arrays, structures, unions) must go on the stack, regardless of registers declared to be holding storage items, if any. (I.e., input registers will be used for integral types, at least, not composite types.)

The first argument must be a pointer to the object. Typically, this flag is used by MSVC's __thiscall convention. Generally, it enforces the fact that the first parameter of a prototype must be a single-slot element (and more specifically, a pointer-type element.

The flag indicates that all float arguments must go on the stack, regardless of registers declared to be holding storage items, if any. (I.e., input registers will be used for integral types, at least, not FP types.)

2+ slots (aka, multi-slot) parameters are disallowed. All inputs must fit on a single slot. Typically, such conventions require composite types to be passed by implicit reference.

3+ slots parameters are disallowed. All inputs must fit on a 1 or 2 slots. Typically, such conventions require larger composite types to be passed by implicit reference.

The flag indicates that the calling convention uses an implicit pointer as first parameter when the function prototype specifies that a "large" composite data type (some fundamental types, all aggregate types) is to be returned. The return value is a pointer to that data. "IPRD" means Implicit Pointer to Return Data.

Example: this method, in x86:

 struct S1 {
     int a, b, c;
 };
 
 struct S1 __cdecl func(struct S1 x) {
     x.c += 1;
     return x;
 }
 

 struct S1* __cdecl_iprd func(struct S1* prd, struct S1 x) {
     x.c += 1;
     copy(prd, &x);
     return prd;
 }
 

This flag indicates that the return-address value is located after the input argument on the stack.

Example:

 | ...
 | return addr
 | argN
 | (...)
 v arg1
 +-----------   <---- SP at routine entry
 

The flag indicates that output values are located on the pre-allocated stack slots located after the input values (whose count may not be known).

Example, when calling a function (int,int)->(int)

 v ...
 +-----------  (SP1)
 | ? retval1 (slot)
 | arg2
 | arg1
 v return addr
 +-----------   <---- SP at routine entry
 

IMPORTANT: this flag requires that all calling convention elements (inputs, outputs, return address) be located on the stack.

This flag indicates that the return values are to be pushed on the stack after return. If it is combined with FLAG_STACK_CLEANED_BY_CALLEE, the input arguments are assumed to be cleaned before pushing the output.

Example, when calling a function (int,int)->(int):

 v ...
 +-----------  (SP1)
 | retaddr
 | arg2
 v arg1
 +-----------   <---- SP at routine entry
 

 v ...
 +-----------  (SP1)
 | retval
 +-----------   <---- SP at return PC
 

The indices in the lists of registers used to pass integral arguments and floating-point arguments grow together, in a parallel fashion.

Example when calling a method: void f(int a, float b, int c, float d)

With the standard x86_64 Windows calling convention, arguments...

 - a would go in rcx
 - b would go in xmm1 (FP reg at index 1)
 - c would go in r8 (GP reg at index 2)
 - d would go in xmm3 (GP reg at index 3)
 

Here is an example of what happens when the general and FP register stacks used for arguments passing grow separately, as is the case for Linux x64, with the standard amd64 System V convention:

 - a would go in rdi
 - b would go in xmm0 (NOT xmm1) 
 - c would go in rsi (NOT rdx) 
 - d would go in xmm1 (NOT xmm3)
 

This flag indicates that candidate input registers that were passed over in favor of stack storage because they were not suitable for an argument at position N, will not be reused for an argument at a later position (>=N+1) even if that argument would be suitable for storage in an unused input register.

An example of that is the x86 fastcall convention on Linux. The first two small integer integer parameters go in ecx and edx; others go on the stack. For a prototype like (int32 a, int64 b, int32 c), a goes in ecx, b on the stack, and c on the stack as well (even though it could fit in edx; note: x86 __fastcall on Windows does not skip over passed input registers; in this example, c would go in edx.}

The flag indicates that the stack is cleaned by the callee (which is not the norm; if the flag is not set, it should be assumed the stack is cleaned by the caller).

Note that a return-address value located on the stack is always pop'ed, regardless of the presence of this flag.

Determine the slotcount alignment requirement of a non-composite type.

Get a list of alternate names for this calling convention.

Get the list of compiler types this calling convention may work with.

Retrieve the optional calling convention, derived from this convention, used to return large composite prototypes. This only applies if the flag FLAG_IPRD was set.

Get an internally-generated identifier for this calling convention object. The id is generated using:

• the same names
• same flags
• same processor targets
• same subsystem targets
• same compiler targets

Return the number of slots that are reserved for parameters. Note that this is just a hint on how many parameters are used.

Create a storage-location generator for the inputs provided to a routine using this calling convention. convention.

Get the common name of this calling convention.

Retrieve all names for this calling convention (principal and alternates).

Convenience method to retrieve the storage location of the single return value for this calling convention. Most calling conventions allow the return of a single value.

Return the number of slots that are reserved for return values. Note that this is just a hint on how many return values are defined.

Create a storage-location generator for the outputs provided to a routine using this calling convention.

Get the list of processor types this calling convention may work with.

Get the list of registers that are spoiled by a callee, in the strictest sense, i.e. their value may or may not be modified, but it is meaningless and should not be interpreted by the caller upon return. That set would NOT include return registers.

Alignment specifications for non-composite types.

Get the list of all registers that may be modified and/or spoiled by a callee, in the most general sense. That set would include any type of return registers.

Get the list of subsystem types this calling convention may work with.

Determine whether this calling convention is compatible with the provided triple (processor, subsystem, compiler).

Determine whether routine parameters pushed on stack before a routine call are cleaned by the callee.

Determine whether routine parameters pushed on stack before a routine call are cleaned by the caller.