This could actually be implemented with the LLVM IR va_arg instruction,
but it doesn't seem to offer any advantages over accessing the va_list
pointer directly.
Using the va_list pointer directly makes it possible to perform type
coercion directly from the argument array, and the va_list updates are
exposed to the optimizers.
llvm-svn: 183292
Type coercion for argument passing is equivalent to storing the source
type and loading the destination type from the same pointer. On
big-endian targets, this means that the high bits of integers are
preserved.
This patch fixes the CoerceIntOrPtrToIntOrPtr() function on big-endian
targets by inserting the required shift instructions to preserve the
high bits instead of the low bits.
This is used by SparcABIInfo when passing small structs in the high bits
of registers.
llvm-svn: 183291
The 'inreg' attribute can also be applied to function return values in
LLVM IR. The SPARC v9 backend is using the flag when returning structs
containing 32-bit floats.
llvm-svn: 183290
The coercion type serves two purposes:
1. Pad structs to a multiple of 64 bits, so they are passed
'left-aligned' in registers.
2. Expose aligned floating point elements as first-level elements, so
the code generator knows to pass them in floating point registers.
We also compute the InReg flag which indicates that the struct contains
aligned 32-bit floats. This flag is used by the code generator to pick
the right registers.
llvm-svn: 182753
- All integer arguments smaller than 64 bits are extended.
- Large structs are passed indirectly, not using 'byval'.
- Structs up to 32 bytes in size are returned in registers.
Some things are not implemented yet:
- EmitVAArg can be implemented in terms of the va_arg instruction.
- When structs are passed in registers, float members require special
handling because they are passed in the floating point registers.
- Structs are left-aligned when passed in registers. This may require
padding.
llvm-svn: 182745
David Blaikie