To make sure that no barrier gets placed on the architectural execution
path, each
BLR x<N>
instruction gets transformed to a
BL __llvm_slsblr_thunk_x<N>
instruction, with __llvm_slsblr_thunk_x<N> a thunk that contains
__llvm_slsblr_thunk_x<N>:
BR x<N>
<speculation barrier>
Therefore, the BLR instruction gets split into 2; one BL and one BR.
This transformation results in not inserting a speculation barrier on
the architectural execution path.
The mitigation is off by default and can be enabled by the
harden-sls-blr subtarget feature.
As a linker is allowed to clobber X16 and X17 on function calls, the
above code transformation would not be correct in case a linker does so
when N=16 or N=17. Therefore, when the mitigation is enabled, generation
of BLR x16 or BLR x17 is avoided.
As BLRA* indirect calls are not produced by LLVM currently, this does
not aim to implement support for those.
Differential Revision: https://reviews.llvm.org/D81402
Some processors may speculatively execute the instructions immediately
following RET (returns) and BR (indirect jumps), even though
control flow should change unconditionally at these instructions.
To avoid a potential miss-speculatively executed gadget after these
instructions leaking secrets through side channels, this pass places a
speculation barrier immediately after every RET and BR instruction.
Since these barriers are never on the correct, architectural execution
path, performance overhead of this is expected to be low.
On targets that implement that Armv8.0-SB Speculation Barrier extension,
a single SB instruction is emitted that acts as a speculation barrier.
On other targets, a DSB SYS followed by a ISB is emitted to act as a
speculation barrier.
These speculation barriers are implemented as pseudo instructions to
avoid later passes to analyze them and potentially remove them.
Even though currently LLVM does not produce BRAA/BRAB/BRAAZ/BRABZ
instructions, these are also mitigated by the pass and tested through a
MIR test.
The mitigation is off by default and can be enabled by the
harden-sls-retbr subtarget feature.
Differential Revision: https://reviews.llvm.org/D81400
Summary:
While clustering mem ops, AMDGPU target needs to consider number of clustered bytes
to decide on max number of mem ops that can be clustered. This patch adds support to pass
number of clustered bytes to target mem ops clustering logic.
Reviewers: foad, rampitec, arsenm, vpykhtin, javedabsar
Reviewed By: foad
Subscribers: MatzeB, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, javed.absar, kerbowa, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80545
When a stack offset was too big to materialize in a single instruction, we were
trying to do it in stages:
adds xD, sp, #imm
adds xD, xD, #imm
Unfortunately, if xD is xzr then the second instruction doesn't exist and
wouldn't do what was needed if it did. Instead we can use a temporary register
for all but the last addition.
Summary:
This patch enables the register allocator to spill/fill lists of 2, 3
and 4 SVE vectors registers to/from the stack. This is implemented with
pseudo instructions that get expanded to individual LDR_ZXI/STR_ZXI
instructions in AArch64ExpandPseudoInsts.
Patch by Sander de Smalen.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D75988
The set of patterns for unpredicated load/store was incomplete: it only
included non-extending stores. Fill out the remaining patterns for
extending stores, and add the corresponding support to frame offset
lowering.
Differential Revision: https://reviews.llvm.org/D80349
The offsets were wrong. The result is now the same as what the compiler
would generate for a function that spills lr normally.
Differential Revision: https://reviews.llvm.org/D80238
When using reversedInstructionsWithoutDebug to construct a range from a
pair of MachineInstrBundleIterators, the range unexpectedly leaves out an
element. This results in mis-optimization as @mstorsjo points out in
https://reviews.llvm.org/D78157.
The problem is that when we convert a MachineInstrBundleIterator to a
reverse iterator, the result gets incremented:
MachineInstrBundleIterator(++I.getReverse())
The comment there explains that the "resulting iterator will dereference
... to the previous node, which is somewhat unexpected; but converting
the two endpoints in a range will give the same range in reverse". This
makes it hard to understand what reversedInstructionsWithoutDebug will
do: I've removed the helper to prevent similar mistakes in the future.
Summary:
This fixes several instances in which condbr optimization was missed
due to a debug instruction appearing as a bogus NZCV clobber.
Reviewers: aemerson, paquette
Subscribers: kristof.beyls, hiraditya, jfb, danielkiss, aprantl, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78264
Summary:
Fix an issue where the presence of debug info could disable a peephole
optimization due to areCFlagsAccessedBetweenInstrs returning the wrong
result.
In test/CodeGen/AArch64/arm64-csel.ll, the issue was found in the
function @foo5, in which the first compare could successfully be
optimized but not the second.
Reviewers: t.p.northover, eastig, paquette
Subscribers: kristof.beyls, hiraditya, danielkiss, aprantl, dsanders, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78157
Summary:
Fix an issue where the presence of debug info could disable a peephole
optimization in optimizeCompareInstr due to canInstrSubstituteCmpInstr
returning the wrong result.
Depends on D78137.
Reviewers: t.p.northover, eastig, paquette
Subscribers: kristof.beyls, hiraditya, danielkiss, aprantl, llvm-commits, dsanders
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78151
Preserving liveness can be useful even late in the pipeline, if we're
doing substantial optimization work afterwards. (See, for example,
D76065.) Teach MachineOutliner how to correctly set live-ins on the
basic block in outlined functions.
Differential Revision: https://reviews.llvm.org/D78605
- Adding changes to support comments on outlined functions with outlining for the conditions through which it was outlined (e.g. Thunks, Tail calls)
- Adapts the emitFunctionHeader to print out a comment next to the header if the target specifies it based on information in MachineFunctionInfo
- Adds mir test for function annotiation
Differential Revision: https://reviews.llvm.org/D78062
[MachineOutliner] fix test for excluding CFI and add test to include CFI in outlining
New test to check that we only outline CFI instruction if all CFI
Instructions in the function would be captured by the outlining
adding x86 tests analagous to AARCH64 cfi tests
Revision: https://reviews.llvm.org/D77852
CFI instructions can only safely be outlined when the outlined call is a tail
call, or when the outlined frame is fixed up.
For the sake of correctness, disable outlining from CFI instructions.
Add machine-outliner-cfi.mir to test this.
Add support for DestructiveBinaryComm DestructiveInstType, as well as the lowering code to expand the new Pseudos into the final movprfx+instruction pairs.
Differential Revision: https://reviews.llvm.org/D73711
Summary:
Making `Scale` a `TypeSize` in AArch64InstrInfo::getMemOpInfo,
has the effect that all places where this information is used
(notably, TargetInstrInfo::getMemOperandWithOffset) will need
to consider Scale - and derived, Offset - possibly being scalable.
This patch adds a new operand `bool &OffsetIsScalable` to
TargetInstrInfo::getMemOperandWithOffset and fixes up all
the places where this function is used, to consider the
offset possibly being scalable.
In most cases, this means bailing out because the algorithm does not
(or cannot) support scalable offsets in places where it does some
form of alias checking for example.
Reviewers: rovka, efriedma, kristof.beyls
Reviewed By: efriedma
Subscribers: wuzish, kerbowa, MatzeB, arsenm, nemanjai, jvesely, nhaehnle, hiraditya, kbarton, javed.absar, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, jsji, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D72758
Scheduler sends NumLoads argument into shouldClusterMemOps()
one less the actual cluster length. So for 2 instructions
it will pass just 1. Correct this number.
This is NFC for in tree targets.
Differential Revision: https://reviews.llvm.org/D73292
This patch also fixes up a number of cases in DAGCombine and
SelectionDAGBuilder where the size of a scalable vector is used in a
fixed-width context (thus triggering an assertion failure).
Reviewers: efriedma, c-rhodes, rovka, cameron.mcinally
Reviewed By: efriedma
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71215
The generic BaseMemOpClusterMutation calls into TargetInstrInfo to
analyze the address of each load/store instruction, and again to decide
whether two instructions should be clustered. Previously this had to
represent each address as a single base operand plus a constant byte
offset. This patch extends it to support any number of base operands.
The old target hook getMemOperandWithOffset is now a convenience
function for callers that are only prepared to handle a single base
operand. It calls the new more general target hook
getMemOperandsWithOffset.
The only requirements for the base operands returned by
getMemOperandsWithOffset are:
- they can be sorted by MemOpInfo::Compare, such that clusterable ops
get sorted next to each other, and
- shouldClusterMemOps knows what they mean.
One simple follow-on is to enable clustering of AMDGPU FLAT instructions
with both vaddr and saddr (base register + offset register). I've left
a FIXME in the code for this case.
Differential Revision: https://reviews.llvm.org/D71655
In GlobalISel we may in some unfortunate circumstances generate PHIs with
operands that are on separate banks. If-conversion doesn't currently check for
that case and ends up generating a CSEL on AArch64 with incorrect register
operands.
Differential Revision: https://reviews.llvm.org/D72961
Summary:
Detect a run of memory tagging instructions for adjacent stack frame slots,
and replace them with a shorter instruction sequence
* replace STG + STG with ST2G
* replace STGloop + STGloop with STGloop
This code needs to run when stack slot offsets are already known, but before
FrameIndex operands in STG instructions are eliminated; that's the
reason for the new hook in PrologueEpilogue.
This change modifies STGloop and STZGloop pseudos to take the size as an
immediate integer operand, and adds _untied variants of those pseudos
that are allowed to take the base address as a FI operand. This is needed to
simplify recognizing an STGloop instruction as operating on a stack slot
post-regalloc.
This improves memtag code size by ~0.25%, and it looks like an additional ~0.1%
is possible by rearranging the stack frame such that consecutive STG
instructions reference adjacent slots (patch pending).
Reviewers: pcc, ostannard
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70286
Summary:
Detect a run of memory tagging instructions for adjacent stack frame slots,
and replace them with a shorter instruction sequence
* replace STG + STG with ST2G
* replace STGloop + STGloop with STGloop
This code needs to run when stack slot offsets are already known, but before
FrameIndex operands in STG instructions are eliminated; that's the
reason for the new hook in PrologueEpilogue.
This change modifies STGloop and STZGloop pseudos to take the size as an
immediate integer operand, and base address as a FI operand when
possible. This is needed to simplify recognizing an STGloop instruction
as operating on a stack slot post-regalloc.
This improves memtag code size by ~0.25%, and it looks like an additional ~0.1%
is possible by rearranging the stack frame such that consecutive STG
instructions reference adjacent slots (patch pending).
Reviewers: pcc, ostannard
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70286
Conservatively always save + restore LR in noreturn functions.
These functions do not end in a RET, and so they aren't guaranteed to have an
instruction which uses LR in any way. So, as a result, you can end up in
unfortunate situations where you can't backtrace out of these functions in a
debugger.
Remove the old noreturn test, and add a new one which is more descriptive.
Remove the restriction that we can't outline from noreturn functions as well
since we now do the right thing.
Summary:
This never really occurs in the current codegen, so only a MIR test is
possible.
Reviewers: ostannard, pcc
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D72123
Summary:
r347747 added support for clustering mem ops with FI base operands
including support for fixed stack objects in shouldClusterFI, but
apparently this was never tested.
This patch fixes shouldClusterFI to work with scaled as well as
unscaled load/store instructions, and fixes the ordering of memory ops
in MemOpInfo::operator< to ensure that memory addresses always
increase, regardless of which direction the stack grows.
Subscribers: MatzeB, kristof.beyls, hiraditya, javed.absar, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71334
This fixes an assertion failure that triggers inside
getMemOperandWithOffset when Machine Sinking calls it on a MachineInstr
that is not a memory operation.
Different backends implement getMemOperandWithOffset differently: some
return false on non-memory MachineInstrs, others assert.
The Machine Sinking pass in at least SinkingPreventsImplicitNullCheck
relies on getMemOperandWithOffset to return false on non-memory
MachineInstrs, instead of asserting.
This patch updates the documentation on getMemOperandWithOffset that it
should return false on any MachineInstr it cannot handle, instead of
asserting. It also adapts the in-tree backends accordingly where
necessary.
Differential Revision: https://reviews.llvm.org/D71359
Summary:
Reland after fixing a bug that allowed outlining of SP modifying instructions
that invalidated return address signing.
During AArch64 frame lowering instructions to enable return address
signing are inserted into functions if needed. Functions generated during
machine outlining don't run through target frame lowering and hence are
missing such instructions.
This patch introduces the following changes:
1. If not all functions that potentially participate in function outlining agree
on their return address signing scope and their return address signing key,
outlining is disabled for these functions.
2. If not all functions that potentially participate in function outlining agree
on their support for v8.3A features, outlining is disabled for these
functions.
3. If an outlining candidate would outline instructions that modify sp in a way
that invalidates return address signing, outlining is disabled for that
particular candidate.
4. If all candidate functions agree on the signing scope, signing key and their
support for v8.3 features, the outlined function behaves as if it had the
same scope and key attributes and as if it would provide the same v8.3A
support as the original functions.
Reviewers: ostannard, paquette
Reviewed By: ostannard
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70635
Summary:
This patch fixes a few issues when large arrays are allocated on the
stack. Currently, clang has inconsistent behaviour, for debug builds
there is an assertion failure when the array size on stack is around 2GB
but there is no assertion when the stack is around 8GB. For release
builds there is no assertion, the compilation succeeds but generates
incorrect code. The incorrect code generated is due to using
int/unsigned int instead of their 64-bit counterparts. This patch,
1) Removes the assertion in frame legality check.
2) Converts int/unsigned int in some places to the 64-bit variants. This
helps in generating correct code and removes the inconsistent behaviour.
3) Adds a test which runs without optimisations.
Reviewers: sdesmalen, efriedma, fhahn, aemerson
Reviewed By: efriedma
Subscribers: eli.friedman, fpetrogalli, kristof.beyls, hiraditya,
llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70496
Summary:
Currently the describeLoadedValue() hook is assumed to describe the
value of the instruction's first explicit define. The hook will not be
called for instructions with more than one explicit define.
This commit adds a register parameter to the describeLoadedValue() hook,
and invokes the hook for all registers in the worklist.
This will allow us to for example describe instructions which produce
more than two parameters' values; e.g. Hexagon's various combine
instructions.
This also fixes situations in our downstream target where we may pass
smaller parameters in the high part of a register. If such a parameter's
value is produced by a larger copy instruction, we can't describe the
call site value using the super-register, and we instead need to know
which sub-register that should be used.
This also allows us to handle cases like this:
$ebx = [...]
$rdi = MOVSX64rr32 $ebx
$esi = MOV32rr $edi
CALL64pcrel32 @call
The hook will first be invoked for the MOV32rr instruction, which will
say that @call's second parameter (passed in $esi) is described by $edi.
As $edi is not preserved it will be added to the worklist. When we get
to the MOVSX64rr32 instruction, we need to describe two values; the
sign-extended value of $ebx -> $rdi for the first parameter, and $ebx ->
$edi for the second parameter, which is now possible.
This commit modifies the dbgcall-site-lea-interpretation.mir test case.
In the test case, the values of some 32-bit parameters were produced
with LEA64r. Perhaps we can in general cases handle such by emitting
expressions that AND out the lower 32-bits, but I have not been able to
land in a case where a LEA64r is used for a 32-bit parameter instead of
LEA64_32 from C code.
I have not found a case where it would be useful to describe parameters
using implicit defines, so in this patch the hook is still only invoked
for explicit defines of forwarding registers.
Reviewers: djtodoro, NikolaPrica, aprantl, vsk
Reviewed By: djtodoro, vsk
Subscribers: ormris, hiraditya, llvm-commits
Tags: #debug-info, #llvm
Differential Revision: https://reviews.llvm.org/D70431
Currently the describeLoadedValue() hook is assumed to describe the
value of the instruction's first explicit define. The hook will not be
called for instructions with more than one explicit define.
This commit adds a register parameter to the describeLoadedValue() hook,
and invokes the hook for all registers in the worklist.
This will allow us to for example describe instructions which produce
more than two parameters' values; e.g. Hexagon's various combine
instructions.
This also fixes a case in our downstream target where we may pass
smaller parameters in the high part of a register. If such a parameter's
value is produced by a larger copy instruction, we can't describe the
call site value using the super-register, and we instead need to know
which sub-register that should be used.
This also allows us to handle cases like this:
$ebx = [...]
$rdi = MOVSX64rr32 $ebx
$esi = MOV32rr $edi
CALL64pcrel32 @call
The hook will first be invoked for the MOV32rr instruction, which will
say that @call's second parameter (passed in $esi) is described by $edi.
As $edi is not preserved it will be added to the worklist. When we get
to the MOVSX64rr32 instruction, we need to describe two values; the
sign-extended value of $ebx -> $rdi for the first parameter, and $ebx ->
$edi for the second parameter, which is now possible.
This commit modifies the dbgcall-site-lea-interpretation.mir test case.
In the test case, the values of some 32-bit parameters were produced
with LEA64r. Perhaps we can in general cases handle such by emitting
expressions that AND out the lower 32-bits, but I have not been able to
land in a case where a LEA64r is used for a 32-bit parameter instead of
LEA64_32 from C code.
I have not found a case where it would be useful to describe parameters
using implicit defines, so in this patch the hook is still only invoked
for explicit defines of forwarding registers.
Summary:
When MUL is the first operand to SUB, we can't use MLS because the accumulator
should be negated. Emit a NEG of the accumulator and an MLA instead, similar to
what we do for FMUL / FSUB fusing.
Reviewers: dmgreen, SjoerdMeijer, fhahn, Gerolf, mstorsjo, asbirlea
Reviewed By: asbirlea
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71067
Summary:
Reland after fixing an ASan failure by stopping outlining early if the
constraints for return address signing removed too many outlining candidates.
During AArch64 frame lowering instructions to enable return address
signing are inserted into functions if needed. Functions generated during
machine outlining don't run through target frame lowering and hence are
missing such instructions.
This patch introduces the following changes:
1. If not all functions that potentially participate in function outlining agree
on their return address signing scope and their return address signing key,
outlining is disabled for these functions.
2. If not all functions that potentially participate in function outlining agree
on their support for v8.3A features, outlining is disabled for these
functions.
3. If an outlining candidate would outline instructions that modify sp in a way
that invalidates return address signing, outlining is disabled for that
particular candidate.
4. If all candidate functions agree on the signing scope, signing key and their
support for v8.3 features, the outlined function behaves as if it had the
same scope and key attributes and as if it would provide the same v8.3A
support as the original functions.
Reviewers: ostannard, paquette
Reviewed By: ostannard
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70635
Summary:
Reland after fixing a bug that allowed outlining of SP modifying instructions
that invalidated return address signing.
During AArch64 frame lowering instructions to enable return address
signing are inserted into functions if needed. Functions generated during
machine outlining don't run through target frame lowering and hence are
missing such instructions.
This patch introduces the following changes:
1. If not all functions that potentially participate in function outlining agree
on their return address signing scope and their return address signing key,
outlining is disabled for these functions.
2. If not all functions that potentially participate in function outlining agree
on their support for v8.3A features, outlining is disabled for these
functions.
3. If an outlining candidate would outline instructions that modify sp in a way
that invalidates return address signing, outlining is disabled for that
particular candidate.
4. If all candidate functions agree on the signing scope, signing key and their
support for v8.3 features, the outlined function behaves as if it had the
same scope and key attributes and as if it would provide the same v8.3A
support as the original functions.
Reviewers: ostannard, paquette
Reviewed By: ostannard
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70635
This patch allows the register allocator to spill SVE registers to the stack.
Reviewers: ostannard, efriedma, rengolin, cameron.mcinally
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D70082
