Previously, it tried to infer the correct destination block from the
successor list, but this is a rather tricky propspect, given the
existence of successors that occur mid-block, such as invoke, and
potentially in the future, callbr/INLINEASM_BR. (INLINEASM_BR, in
particular would be problematic, because its successor blocks are not
distinct from "normal" successors, as EHPads are.)
Instead, require the caller to pass in the expected fallthrough
successor explicitly. In most callers, the correct block is
immediately clear. But, in MachineBlockPlacement, we do need to record
the original ordering, before starting to reorder blocks.
Unfortunately, the goal of decoupling the behavior of end-of-block
jumps from the successor list has not been fully accomplished in this
patch, as there is currently no other way to determine whether a block
is intended to fall-through, or end as unreachable. Further work is
needed there.
Differential Revision: https://reviews.llvm.org/D79605
This patch adds clang options:
-fbasic-block-sections={all,<filename>,labels,none} and
-funique-basic-block-section-names.
LLVM Support for basic block sections is already enabled.
+ -fbasic-block-sections={all, <file>, labels, none} : Enables/Disables basic
block sections for all or a subset of basic blocks. "labels" only enables
basic block symbols.
+ -funique-basic-block-section-names: Enables unique section names for
basic block sections, disabled by default.
Differential Revision: https://reviews.llvm.org/D68049
in the same section.
This allows specifying BasicBlock clusters like the following example:
!foo
!!0 1 2
!!4
This places basic blocks 0, 1, and 2 in one section in this order, and
places basic block #4 in a single section of its own.
This is the second patch in a series of patches to enable basic block
sections support.
This patch adds support for:
* Creating direct jumps at the end of basic blocks that have fall
through instructions.
* New pass, bbsections-prepare, that analyzes placement of basic blocks
in sections.
* Actual placing of a basic block in a unique section with special
handling of exception handling blocks.
* Supports placing a subset of basic blocks in a unique section.
* Support for MIR serialization and deserialization with basic block
sections.
Parent patch : D68063
Differential Revision: https://reviews.llvm.org/D73674
