This adds some more scalar instructions that are both associative and
commutative to isAssociativeAndCommutative, allowing the machine
combiner to reassociate them to reduce critical path length.
Differential Revision: https://reviews.llvm.org/D134260
This adds some more scalar instructions that are both associative and
commutative to isAssociativeAndCommutative, allowing the machine
combiner to reassociate them to reduce critical path length.
Differential Revision: https://reviews.llvm.org/D134260
Re-commit of 32e8b550e5439c7e4aafa73894faffd5f25d0d05
This patch rearranges emission of CFI instructions, so the resulting
DWARF and `.eh_frame` information is precise at every instruction.
The current state is that the unwind info is emitted only after the
function prologue. This is fine for synchronous (e.g. C++) exceptions,
but the information is generally incorrect when the program counter is
at an instruction in the prologue or the epilogue, for example:
```
stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
mov x29, sp
.cfi_def_cfa w29, 16
...
```
after the `stp` is executed the (initial) rule for the CFA still says
the CFA is in the `sp`, even though it's already offset by 16 bytes
A correct unwind info could look like:
```
stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
.cfi_def_cfa_offset 16
mov x29, sp
.cfi_def_cfa w29, 16
...
```
Having this information precise up to an instruction is useful for
sampling profilers that would like to get a stack backtrace. The end
goal (towards this patch is just a step) is to have fully working
`-fasynchronous-unwind-tables`.
Reviewed By: danielkiss, MaskRay
Differential Revision: https://reviews.llvm.org/D111411
It caused builds to assert with:
(StackSize == 0 && "We already have the CFA offset!"),
function generateCompactUnwindEncoding, file AArch64AsmBackend.cpp, line 624.
when targeting iOS. See comment on the code review for reproducer.
> This patch rearranges emission of CFI instructions, so the resulting
> DWARF and `.eh_frame` information is precise at every instruction.
>
> The current state is that the unwind info is emitted only after the
> function prologue. This is fine for synchronous (e.g. C++) exceptions,
> but the information is generally incorrect when the program counter is
> at an instruction in the prologue or the epilogue, for example:
>
> ```
> stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
> mov x29, sp
> .cfi_def_cfa w29, 16
> ...
> ```
>
> after the `stp` is executed the (initial) rule for the CFA still says
> the CFA is in the `sp`, even though it's already offset by 16 bytes
>
> A correct unwind info could look like:
> ```
> stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
> .cfi_def_cfa_offset 16
> mov x29, sp
> .cfi_def_cfa w29, 16
> ...
> ```
>
> Having this information precise up to an instruction is useful for
> sampling profilers that would like to get a stack backtrace. The end
> goal (towards this patch is just a step) is to have fully working
> `-fasynchronous-unwind-tables`.
>
> Reviewed By: danielkiss, MaskRay
>
> Differential Revision: https://reviews.llvm.org/D111411
This reverts commit 32e8b550e5439c7e4aafa73894faffd5f25d0d05.
This patch rearranges emission of CFI instructions, so the resulting
DWARF and `.eh_frame` information is precise at every instruction.
The current state is that the unwind info is emitted only after the
function prologue. This is fine for synchronous (e.g. C++) exceptions,
but the information is generally incorrect when the program counter is
at an instruction in the prologue or the epilogue, for example:
```
stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
mov x29, sp
.cfi_def_cfa w29, 16
...
```
after the `stp` is executed the (initial) rule for the CFA still says
the CFA is in the `sp`, even though it's already offset by 16 bytes
A correct unwind info could look like:
```
stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
.cfi_def_cfa_offset 16
mov x29, sp
.cfi_def_cfa w29, 16
...
```
Having this information precise up to an instruction is useful for
sampling profilers that would like to get a stack backtrace. The end
goal (towards this patch is just a step) is to have fully working
`-fasynchronous-unwind-tables`.
Reviewed By: danielkiss, MaskRay
Differential Revision: https://reviews.llvm.org/D111411
Add a comment when there is a shifted value,
add x9, x0, #291, lsl #12 ; =1191936
but not when the immediate value is unshifted,
subs x9, x0, #256 ; =256
when the comment adds nothing additional to the reader.
Differential Revision: https://reviews.llvm.org/D107196
Since d6de1e1a71406c75a4ea4d5a2fe84289f07ea3a1, no attributes is quivalent to
setting attribute to false.
This is a preliminary commit for https://reviews.llvm.org/D99080
Changes:
There was a condition for `!NeedsFrameRecord` missing in the assert. The
assert in question has changed to:
+ assert((!RPI.isPaired() || !NeedsFrameRecord || RPI.Reg2 != AArch64::FP ||
+ RPI.Reg1 == AArch64::LR) &&
+ "FrameRecord must be allocated together with LR");
This addresses PR43016.
llvm-svn: 369122
This patch changes the location of the frame-record (FP, LR) to the
bottom of the callee-saved area. According to the AAPCS the location of
the frame-record within the stackframe is unspecified (section 5.2.3 The
Frame Pointer), so the compiler should be free to choose a different
location.
The reason for changing the location of the frame-record is to prepare
the frame for allocating an SVE area below the callee-saves. This way the
compiler can use the VL-scaled addressing modes to directly access SVE
objects from the frame-pointer.
: :
| stack | | stack |
| args | | args |
+-------+ +-------+
| x30 | | x19 |
| x29 | | x20 |
FP -> |- - - -| | x21 |
| x19 | ==> | x22 |
| x20 | |- - - -|
| x21 | | x30 |
| x22 | | x29 |
+-------+ +-------+ <- FP
|///////| |///////| // realignment gap
|- - - -| |- - - -|
|spills/| |spills/|
| locals| | locals|
SP -> +-------+ +-------+ <- SP
Things to point out:
- The algorithm to find a paired register should be prevented from
accidentally pairing some callee-saved register with LR that is not
FP, since they should always be paired together when the frame
has a frame-record.
- For Darwin platforms the location of the frame-record is unchanged,
since the unwind encoding does not allow for encoding this position
dynamically and other tools currently depend on the former layout.
Reviewers: efriedma, rovka, rengolin, thegameg, greened, t.p.northover
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D65653
llvm-svn: 368987
Part of the effort to refactoring frame pointer code generation. We used
to use two function attributes "no-frame-pointer-elim" and
"no-frame-pointer-elim-non-leaf" to represent three kinds of frame
pointer usage: (all) frames use frame pointer, (non-leaf) frames use
frame pointer, (none) frame use frame pointer. This CL makes the idea
explicit by using only one enum function attribute "frame-pointer"
Option "-frame-pointer=" replaces "-disable-fp-elim" for tools such as
llc.
"no-frame-pointer-elim" and "no-frame-pointer-elim-non-leaf" are still
supported for easy migration to "frame-pointer".
tests are mostly updated with
// replace command line args ‘-disable-fp-elim=false’ with ‘-frame-pointer=none’
grep -iIrnl '\-disable-fp-elim=false' * | xargs sed -i '' -e "s/-disable-fp-elim=false/-frame-pointer=none/g"
// replace command line args ‘-disable-fp-elim’ with ‘-frame-pointer=all’
grep -iIrnl '\-disable-fp-elim' * | xargs sed -i '' -e "s/-disable-fp-elim/-frame-pointer=all/g"
Patch by Yuanfang Chen (tabloid.adroit)!
Differential Revision: https://reviews.llvm.org/D56351
llvm-svn: 351049
Summary:
If the target requests it, use emptry spaces in the fixed and
callee-save stack area to allocate local stack objects.
AArch64: Change last callee-save reg stack object alignment instead of
size to leave a gap to take advantage of above change.
Reviewers: t.p.northover, qcolombet, MatzeB
Subscribers: rengolin, mcrosier, llvm-commits, aemerson
Differential Revision: http://reviews.llvm.org/D20220
llvm-svn: 271527
Summary:
If a function needs to allocate both callee-save stack memory and local
stack memory, we currently decrement/increment the SP in two steps:
first for the callee-save area, and then for the local stack area. This
changes the code to allocate them both at once at the very beginning/end
of the function. This has two benefits:
1) there is one fewer sub/add micro-op in the prologue/epilogue
2) the stack adjustment instructions act as a scheduling barrier, so
moving them to the very beginning/end of the function increases post-RA
scheduler's ability to move instructions (that only depend on argument
registers) before any of the callee-save stores
This change can cause an increase in instructions if the original local
stack SP decrement could be folded into the first store to the stack.
This occurs when the first local stack store is to stack offset 0. In
this case we are trading off one more sub instruction for one fewer sub
micro-op (along with benefits (2) and (3) above).
Reviewers: t.p.northover
Subscribers: aemerson, rengolin, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18619
llvm-svn: 268746
Summary:
This change enables frame pointer elimination in non-leaf functions.
The -fomit-frame-pointer option still needs to be used when compiling
via clang (or an equivalent method of not setting the
'no-frame-pointer-elim*' function attributes if generating llvm IR via
some other method) to take advantage of this optimization.
This change should be NFC when compiling via clang without
-fomit-frame-pointer.
Reviewers: t.p.northover
Subscribers: aemerson, rengolin, tberghammer, qcolombet, llvm-commits, danalbert, mcrosier, srhines
Differential Revision: http://reviews.llvm.org/D17730
llvm-svn: 262495
Summary:
Before this change, callee-save registers would be rounded up to even
pairs of GPRs and FPRs. This change eliminates these extra padding
load/stores, though it does keep the stack allocation the same size
unless both the GPR and FPR sets have an odd size, in which case one
full pair stack slot (16 bytes) is saved.
This optimization cannot currently be done for MachO targets since they
rely on a fast-path .debug_frame equivalent that can only encode
callee-save registers as pairs.
Reviewers: t.p.northover, rengolin, mcrosier, jmolloy
Subscribers: aemerson, rengolin, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D17000
llvm-svn: 260689
Disable post-ra scheduler for perturbed tests to appease the bots and to
preserve the history of the tests.
http://reviews.llvm.org/D15652
llvm-svn: 256158
It's potentially more efficient on Cyclone, and from the optimization guides &
schedulers looks like it has no effect on Cortex-A53 or A57. In general you'd
expect a MOV to be about the most efficient instruction with its semantics,
even though the official "UXTW" alias is really a UBFX.
llvm-svn: 243576
Fixes PR23804: assertion failure in emitPrologue in the case of a
function with an empty frame and a dynamic alloca that needs stack
realignment. This is a typical case for AddressSanitizer.
llvm-svn: 241943
If our two inputs have known top-zero bit counts M and N, we trivially
know that the output cannot have any bits set in the top (min(M, N)-1)
bits, since nothing could carry past that point.
llvm-svn: 241927
