Deprecation Notices

This section contains information about deprecation of behaviours, features and APIs that have become undesirable/obsolete. Any information about the schedule for their deprecation and reasoning behind the changes, along with examples, is provided.

Deprecation of use of memset/memcpy llvm intrinsic with specified alignment

From LLVM 7 onward the memset and memcpy intrinsics dropped the use of an alignment, specified as the third argument, and instead use the alignment of the first argument for this purpose. Specifying the alignment in third argument continued to work as LLVM auto-updates this use case.

Reason for deprecation

LLVM has changed the behaviour of the previously mentioned intrinsics, and so as to increase compatibility with future releases of LLVM, llvmlite is adapting to match.

Example(s) of the impact

At present the following works:

from llvmlite import ir

bit = ir.IntType(1)
int8 = ir.IntType(8)
int32 = ir.IntType(32)
int64 = ir.IntType(64)
int8ptr = int8.as_pointer()

mod = ir.Module()
fnty = ir.FunctionType(int32, ())
func = ir.Function(mod, fnty, "some_function")
block = func.append_basic_block('some_block')
builder = ir.IRBuilder(block)

some_address = int64(0xdeaddead)
dest = builder.bitcast(some_address, int8ptr)
value = int8(0xa5)
memset = mod.declare_intrinsic('llvm.memset', [int8ptr, int32])
memcpy = mod.declare_intrinsic('llvm.memcpy', [int8ptr, int8ptr, int32])

# NOTE: 5 argument call site (dest, value, length, align, isvolatile)
builder.call(memset, [dest, value, int32(10), int32(0), bit(0)])

some_other_address = int64(0xcafecafe)
src = builder.bitcast(some_other_address, int8ptr)

# NOTE: 5 argument call site (dest, src, length, align, isvolatile)
builder.call(memcpy, [dest, src, int32(10), int32(0), bit(0)])

builder.ret(int32(0))
print(str(mod))

In future only the following will work:

from llvmlite import ir

bit = ir.IntType(1)
int8 = ir.IntType(8)
int32 = ir.IntType(32)
int64 = ir.IntType(64)
int8ptr = int8.as_pointer()

mod = ir.Module()
fnty = ir.FunctionType(int32, ())
func = ir.Function(mod, fnty, "some_function")
block = func.append_basic_block('some_block')
builder = ir.IRBuilder(block)

some_address = int64(0xdeaddead)
dest = builder.bitcast(some_address, int8ptr)
value = int8(0xa5)
memset = mod.declare_intrinsic('llvm.memset', [int8ptr, int32])
memcpy = mod.declare_intrinsic('llvm.memcpy', [int8ptr, int8ptr, int32])

# NOTE: 4 argument call site (dest, value, length, isvolatile)
builder.call(memset, [dest, value, int32(10), bit(0)])

some_other_address = int64(0xcafecafe)
src = builder.bitcast(some_other_address, int8ptr)

# NOTE: 4 argument call site (dest, src, length, isvolatile)
builder.call(memcpy, [dest, src, int32(10), bit(0)])

builder.ret(int32(0))
print(str(mod))

Schedule

This feature will be removed with respect to this schedule:

• v0.30 will be the last release to support an alignment specified as the third argument (5 argument style).
• v0.31 will support the 4 argument style call only.

Recommendations

Projects that need/rely on the deprecated behaviour should pin their dependency on llvmlite to a version prior to removal of this behaviour.