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Define stack_load, stack_store, and stack_addr instructions.

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Jakob Stoklund Olesen
2017-04-10 13:20:41 -07:00
parent af2516e996
commit c52e3e0b3f
10 changed files with 163 additions and 56 deletions
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docs/langref.rst
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@@ -489,33 +489,8 @@ simply represent a contiguous sequence of bytes in the stack frame.
:flag align(N): Request at least N bytes alignment.
:result SS: Stack slot index.
.. inst:: a = stack_load SS, Offset
Load a value from a stack slot at the constant offset.
This is a polymorphic instruction that can load any value type which has a
memory representation.
The offset is an immediate constant, not an SSA value. The memory access
cannot go out of bounds, i.e. ``sizeof(a) + Offset <= sizeof(SS)``.
:arg SS: Stack slot declared with :inst:`stack_slot`.
:arg Offset: Immediate non-negative offset.
:result T a: Value loaded.
.. inst:: stack_store x, SS, Offset
Store a value to a stack slot at a constant offset.
This is a polymorphic instruction that can store any value type with a
memory representation.
The offset is an immediate constant, not an SSA value. The memory access
cannot go out of bounds, i.e. ``sizeof(a) + Offset <= sizeof(SS)``.
:arg T x: Value to be stored.
:arg SS: Stack slot declared with :inst:`stack_slot`.
:arg Offset: Immediate non-negative offset.
.. autoinst:: stack_load
.. autoinst:: stack_store
The dedicated stack access instructions are easy for the compiler to reason
about because stack slots and offsets are fixed at compile time. For example,
@@ -525,16 +500,7 @@ and stack slot alignments.
It can be necessary to escape from the safety of the restricted instructions by
taking the address of a stack slot.
.. inst:: a = stack_addr SS, Offset
Get the address of a stack slot.
Compute the absolute address of a byte in a stack slot. The offset must
refer to a byte inside the stack slot: ``0 <= Offset < sizeof(SS)``.
:arg SS: Stack slot declared with :inst:`stack_slot`.
:arg Offset: Immediate non-negative offset.
:result iPtr a: Address.
.. autoinst:: stack_addr
The :inst:`stack_addr` instruction can be used to macro-expand the stack access
instructions before instruction selection::