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Document which instructions are meant for producers to use.

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This reorganizes some things in ir.rst to put all instructions not meant
for frontends to worry about in a dedicated section.

Fixes #282.
This commit is contained in:
Dan Gohman
2018-11-28 06:04:31 -08:00
parent f028c53479
commit 7c03ba43be
1 changed files with 74 additions and 60 deletions
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134
cranelift/docs/ir.rst
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@@ -352,12 +352,9 @@ condition is satisfied, otherwise execution continues at the following
instruction in the EBB.
.. autoinst:: jump
.. autoinst:: fallthrough
.. autoinst:: brz
.. autoinst:: brnz
.. autoinst:: br_icmp
.. autoinst:: brif
.. autoinst:: brff
.. autoinst:: br_table
.. inst:: JT = jump_table [EBB0, EBB1, ..., EBBn]
@@ -384,8 +381,6 @@ is zero.
.. autoinst:: trap
.. autoinst:: trapz
.. autoinst:: trapnz
.. autoinst:: trapif
.. autoinst:: trapff
Function calls
@@ -803,34 +798,6 @@ load a constant into an SSA value.
.. autoinst:: f64const
.. autoinst:: bconst
Live range splitting
--------------------
Cranelift's register allocator assigns each SSA value to a register or a spill
slot on the stack for its entire live range. Since the live range of an SSA
value can be quite large, it is sometimes beneficial to split the live range
into smaller parts.
A live range is split by creating new SSA values that are copies or the
original value or each other. The copies are created by inserting :inst:`copy`,
:inst:`spill`, or :inst:`fill` instructions, depending on whether the values
are assigned to registers or stack slots.
This approach permits SSA form to be preserved throughout the register
allocation pass and beyond.
.. autoinst:: copy
.. autoinst:: spill
.. autoinst:: fill
Register values can be temporarily diverted to other registers by the
:inst:`regmove` instruction, and to and from stack slots by :inst:`regspill`
and :inst:`regfill`.
.. autoinst:: regmove
.. autoinst:: regspill
.. autoinst:: regfill
Vector operations
-----------------
@@ -988,12 +955,6 @@ represented as a floating point number.
.. autoinst:: trunc
.. autoinst:: nearest
CPU flag operations
-------------------
.. autoinst:: trueif
.. autoinst:: trueff
Conversion operations
---------------------
@@ -1014,27 +975,6 @@ Conversion operations
.. autoinst:: fcvt_from_uint
.. autoinst:: fcvt_from_sint
Legalization operations
-----------------------
These instructions are used as helpers when legalizing types and operations for
the target ISA.
.. autoinst:: isplit
.. autoinst:: iconcat
Special register operations
---------------------------
The prologue and epilogue of a function needs to manipulate special registers like the stack
pointer and the frame pointer. These instructions should not be used in regular code.
.. autoinst:: adjust_sp_down
.. autoinst:: adjust_sp_up_imm
.. autoinst:: adjust_sp_down_imm
.. autoinst:: ifcmp_sp
.. autoinst:: copy_special
.. _extload-truncstore:
Extending loads and truncating stores
@@ -1082,6 +1022,80 @@ Instructions that can only be used by the x86 target ISA.
.. autoinst:: isa.x86.instructions.push
.. autoinst:: isa.x86.instructions.pop
Codegen implementation instructions
===================================
Frontends don't need to emit the instructions in this section themselves;
Cranelift will generate them automatically as needed.
Legalization operations
-----------------------
These instructions are used as helpers when legalizing types and operations for
the target ISA.
.. autoinst:: isplit
.. autoinst:: iconcat
Special register operations
---------------------------
The prologue and epilogue of a function needs to manipulate special registers like the stack
pointer and the frame pointer. These instructions should not be used in regular code.
.. autoinst:: adjust_sp_down
.. autoinst:: adjust_sp_up_imm
.. autoinst:: adjust_sp_down_imm
.. autoinst:: ifcmp_sp
.. autoinst:: copy_special
Low-level control flow operations
---------------------------------
.. autoinst:: fallthrough
CPU flag operations
-------------------
These operations are for working with the "flags" registers of some CPU
architectures.
.. autoinst:: trueif
.. autoinst:: trueff
.. autoinst:: trapif
.. autoinst:: trapff
.. autoinst:: brif
.. autoinst:: brff
Live range splitting
--------------------
Cranelift's register allocator assigns each SSA value to a register or a spill
slot on the stack for its entire live range. Since the live range of an SSA
value can be quite large, it is sometimes beneficial to split the live range
into smaller parts.
A live range is split by creating new SSA values that are copies or the
original value or each other. The copies are created by inserting :inst:`copy`,
:inst:`spill`, or :inst:`fill` instructions, depending on whether the values
are assigned to registers or stack slots.
This approach permits SSA form to be preserved throughout the register
allocation pass and beyond.
.. autoinst:: copy
.. autoinst:: spill
.. autoinst:: fill
Register values can be temporarily diverted to other registers by the
:inst:`regmove` instruction, and to and from stack slots by :inst:`regspill`
and :inst:`regfill`.
.. autoinst:: regmove
.. autoinst:: regspill
.. autoinst:: regfill
Instruction groups
==================