tqchen commented on issue #7246:
URL: https://github.com/apache/tvm/issues/7246#issuecomment-784223136
The function will looks like
```
fn myfunc() {
for i in range(10):
stack_tcode = @tir.packed_arg_alloca("arg_tcode", 8)
stack_value = @tir.packed_arg_alloca("arg_value", 8)
tir.tvm_call_packed_lowered("tvm.contrib.cblas.matmul", stack_1)
}
```
In the LLVM code generator, we want the compiled code to look like
```
fn myfunc() {
begin:
stack_tcode0 = alloca("arg_tcode", 8)
stack_value1 = alloca("arg_value", 8)
loop:
for i in range(10):
tir.tvm_call_packed_lowered("tvm.contrib.cblas.matmul", stack_1)
}
```
This can be done by jumping to the function begin basic block for insertion.
https://github.com/apache/tvm/blob/81d9f11ab87dc3ef5fc906aa6ca23737885f7b27/src/target/llvm/codegen_llvm.h#L173
Note that this is a restriction of LLVM IR(alloca always happens in the
beginning of the function). Additionally, we could certainly coleasce the stack
of multiple calls, although LLVM could do that for us so we do not need to do
so.
Note that in the case of parallel, a new function will be created for the
parallel body, and WithFunctionEntry will get the alloca inserted at the
beginning of that function. This is the benefit of delaying the alloca location
move until the code gen point.
For the case of StackVM, we could certainly directly grow the stack at
callsite. For the case of C generator, depending on the restriction of
language, we might also need to create allocation in the beginning (e.g. create
a init fragement stream of a function that is separated from the rest).
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