In the motivating case from https://llvm.org/PR47517
we create a node that does not get constant folded
before getNegatedExpression is attempted from some
other node, and we crash.
By moving the fold into SelectionDAG::simplifyFPBinop(),
we get the constant fold sooner and avoid the problem.
This is similar to D87251, but for CopyFromRegs nodes.
Even for local statepoint uses we generate CopyToRegs/CopyFromRegs
nodes. When generating CopyFromRegs in visitGCRelocate, we must chain
to current DAG root, not EntryNode, to ensure proper ordering of copy
w.r.t. statepoint node producing result for it.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D88639
The TypePromotion pass only operates on scalar types so I've fixed up
all places where we were relying upon the implicit cast from
TypeSize->uint64_t.
Differential Revision: https://reviews.llvm.org/D88575
When we know that a particular type is always going to be fixed
width we have so far been writing code like this:
getSizeInBits().getFixedSize()
Since we are doing this in quite a few places now it seems to make
sense to add a new helper function that allows us to replace
these calls with a single getFixedSizeInBits() call.
Differential Revision: https://reviews.llvm.org/D88649
Summary:
Some design decision worth noting about:
I've noticed a recent mailing discussing about why string literal is
not affected by -fdata-sections for ELF target:
http://lists.llvm.org/pipermail/llvm-dev/2020-September/145121.html
But on AIX, our linker could not split the mergeable string like other target.
So I think it would make more sense for us to emit separate csect for
every mergeable string in -fdata-sections mode,
as there might not be other ways for linker to do garbage collection
on unused mergeable string.
Reviewed By: daltenty, hubert.reinterpretcast
Differential Revision: https://reviews.llvm.org/D88339
We don't support global variables with scalable vector types so I've
changed the code to compare the fixed sizes instead.
Differential Revision: https://reviews.llvm.org/D88564
This patch adds support for creating Guard Address-Taken IAT Entry Tables (.giats$y sections) in object files, matching the behavior of MSVC. These contain lists of address-taken imported functions, which are used by the linker to create the final GIATS table.
Additionally, if any DLLs are delay-loaded, the linker must look through the .giats tables and add the respective load thunks of address-taken imports to the GFIDS table, as these are also valid call targets.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D87544
This patch adds FP_EXTEND_MERGE_PASSTHRU & FP_ROUND_MERGE_PASSTHRU
ISD nodes, used to lower scalable vector fp_extend/fp_round operations.
fp_round has an additional argument, the 'trunc' flag, which is an integer of zero or one.
This also fixes a warning introduced by the new tests added to sve-split-fcvt.ll,
resulting from an implicit TypeSize -> uint64_t cast in SplitVecOp_FP_ROUND.
Reviewed By: sdesmalen, paulwalker-arm
Differential Revision: https://reviews.llvm.org/D88321
This is part of the Propeller framework to do post link code layout optimizations. Please see the RFC here: https://groups.google.com/forum/#!msg/llvm-dev/ef3mKzAdJ7U/1shV64BYBAAJ and the detailed RFC doc here: https://github.com/google/llvm-propeller/blob/plo-dev/Propeller_RFC.pdf
This patch provides exception support for basic block sections by splitting the call-site table into call-site ranges corresponding to different basic block sections. Still all landing pads must reside in the same basic block section (which is guaranteed by the the core basic block section patch D73674 (ExceptionSection) ). Each call-site table will refer to the landing pad fragment by explicitly specifying @LPstart (which is omitted in the normal non-basic-block section case). All these call-site tables will share their action and type tables.
The C++ ABI somehow assumes that no landing pads point directly to LPStart (which works in the normal case since the function begin is never a landing pad), and uses LP.offset = 0 to specify no landing pad. In the case of basic block section where one section contains all the landing pads, the landing pad offset relative to LPStart could actually be zero. Thus, we avoid zero-offset landing pads by inserting a **nop** operation as the first non-CFI instruction in the exception section.
**Background on Exception Handling in C++ ABI**
https://github.com/itanium-cxx-abi/cxx-abi/blob/master/exceptions.pdf
Compiler emits an exception table for every function. When an exception is thrown, the stack unwinding library queries the unwind table (which includes the start and end of each function) to locate the exception table for that function.
The exception table includes a call site table for the function, which is used to guide the exception handling runtime to take the appropriate action upon an exception. Each call site record in this table is structured as follows:
| CallSite | --> Position of the call site (relative to the function entry)
| CallSite length | --> Length of the call site.
| Landing Pad | --> Position of the landing pad (relative to the landing pad fragment’s begin label)
| Action record offset | --> Position of the first action record
The call site records partition a function into different pieces and describe what action must be taken for each callsite. The callsite fields are relative to the start of the function (as captured in the unwind table).
The landing pad entry is a reference into the function and corresponds roughly to the catch block of a try/catch statement. When execution resumes at a landing pad, it receives an exception structure and a selector value corresponding to the type of the exception thrown, and executes similar to a switch-case statement. The landing pad field is relative to the beginning of the procedure fragment which includes all the landing pads (@LPStart). The C++ ABI requires all landing pads to be in the same fragment. Nonetheless, without basic block sections, @LPStart is the same as the function @Start (found in the unwind table) and can be omitted.
The action record offset is an index into the action table which includes information about which exception types are caught.
**C++ Exceptions with Basic Block Sections**
Basic block sections break the contiguity of a function fragment. Therefore, call sites must be specified relative to the beginning of the basic block section. Furthermore, the unwinding library should be able to find the corresponding callsites for each section. To do so, the .cfi_lsda directive for a section must point to the range of call-sites for that section.
This patch introduces a new **CallSiteRange** structure which specifies the range of call-sites which correspond to every section:
`struct CallSiteRange {
// Symbol marking the beginning of the precedure fragment.
MCSymbol *FragmentBeginLabel = nullptr;
// Symbol marking the end of the procedure fragment.
MCSymbol *FragmentEndLabel = nullptr;
// LSDA symbol for this call-site range.
MCSymbol *ExceptionLabel = nullptr;
// Index of the first call-site entry in the call-site table which
// belongs to this range.
size_t CallSiteBeginIdx = 0;
// Index just after the last call-site entry in the call-site table which
// belongs to this range.
size_t CallSiteEndIdx = 0;
// Whether this is the call-site range containing all the landing pads.
bool IsLPRange = false;
};`
With N basic-block-sections, the call-site table is partitioned into N call-site ranges.
Conceptually, we emit the call-site ranges for sections sequentially in the exception table as if each section has its own exception table. In the example below, two sections result in the two call site ranges (denoted by LSDA1 and LSDA2) placed next to each other. However, their call-sites will refer to records in the shared Action Table. We also emit the header fields (@LPStart and CallSite Table Length) for each call site range in order to place the call site ranges in separate LSDAs. We note that with -basic-block-sections, The CallSiteTableLength will not actually represent the length of the call site table, but rather the reference to the action table. Since the only purpose of this field is to locate the action table, correctness is guaranteed.
Finally, every call site range has one @LPStart pointer so the landing pads of each section must all reside in one section (not necessarily the same section). To make this easier, we decide to place all landing pads of the function in one section (hence the `IsLPRange` field in CallSiteRange).
| @LPStart | ---> Landing pad fragment ( LSDA1 points here)
| CallSite Table Length | ---> Used to find the action table.
| CallSites |
| … |
| … |
| @LPStart | ---> Landing pad fragment ( LSDA2 points here)
| CallSite Table Length |
| CallSites |
| … |
| … |
…
…
| Action Table |
| Types Table |
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D73739
All the state of VRAI is allocator-wide, so we can avoid creating it
every time we need it. In addition, the normalization function is
allocator-specific. In a next change, we can simplify that design in
favor of just having it as a virtual member.
Differential Revision: https://reviews.llvm.org/D88499
This allows LiveDebugValues to insert the proper DBG_VALUEs in live
out blocks if a spill is inserted before the use of a
register. Previously, this would see the register use as the last
DBG_VALUE, even though the stack slot should be treated as the live
out value.
This avoids an lldb test regression when D52010 is re-applied.
Before, for each original argument i, ValNo was set to i + PartIdx, but
ValNo is intended to reflect the index of the value before splitting.
Hence, ValNo should always be set to i and not consider the PartIdx.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D86511
We weren't looking at global uses of a value, so we could happily
overwrite the register incorrectly.
Differential Revision: https://reviews.llvm.org/D88554
Following on from D87757 "[SplitKit] Only copy live lanes", it is
possible to split a live range at a point when none of its subranges
are live. This patch handles that case by inserting an implicit def
of the superreg.
Patch by Quentin Colombet!
Differential Revision: https://reviews.llvm.org/D88397
So forwards is forwards and backwards is reverse. Also add a check
so that we know the instructions are in the expected order.
Differential Revision: https://reviews.llvm.org/D88419
During lowering of G_UMULO and friends, the previous code moved the builder's
insertion point to be after the legalizing instruction. When that happened, if
there happened to be a "G_CONSTANT i32 0" immediately after, the CSEMIRBuilder
would try to find that constant during the buildConstant(zero) call, and since
it dominates itself would return the iterator unchanged, even though the def
of the constant was *after* the current insertion point. This resulted in the
compare being generated *before* the constant which it was using.
There's no need to modify the insertion point before building the mul-hi or
constant. Delaying moving the insert point ensures those are built/CSEd before
the G_ICMP is built.
Fixes PR47679
Differential Revision: https://reviews.llvm.org/D88514
Added unittests. In the process, separated core construction - which just
needs the hits, order, and 'HardHints' values - from construction from
current register allocation state, to simplify testing.
Differential Revision: https://reviews.llvm.org/D88455
Fix creation of illegal unmerge when widen was requested to a type which
is not a multiple of the destination type. E.g. when trying to widen
an s48 unmerge to s64 the existing code would create an illegal unmerge
from s64 to s48.
Instead, create further unmerges to a GCD type, then use this to remerge
these intermediate results to the actual destinations.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D88422
When extending the subranges, the reaching-def may be an undefs. When
extending such kind of subrange, it will try to search for the reaching
def first. If the reaching def is an undef and we did not provide 'Undefs',
The findReachingDefs() will fail with message:
"Use of $noreg does not have a corresponding definition on every path:
LLVM ERROR: Use not jointly dominated by defs."
So we computeSubRangeUndefs() and pass the result to extendToIndices().
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D87744
When we see this:
```
%and = G_AND %x, %y
%xor = G_XOR %and, %y
```
Produce this:
```
%not = G_XOR %x, -1
%new_and = G_AND %not, %y
```
as long as we are guaranteed to eliminate the original G_AND.
Also matches all commuted forms. E.g.
```
%and = G_AND %y, %x
%xor = G_XOR %y, %and
```
will be matched as well.
Differential Revision: https://reviews.llvm.org/D88104
After some recent upstream discussion we decided that it was best
to avoid having the / operator for both ElementCount and TypeSize,
since this could give the impression that these classes can be used
in the same way as basic integer integer types. However, division
for scalable types is a bit odd because we are only dividing the
minimum quantity by a value, as opposed to something like:
(MinSize * Vscale) / SomeValue
This is why when performing division it's important the caller
first establishes whether the operation makes sense, perhaps by
calling isKnownMultipleOf() prior to division. The caller must now
explictly call divideCoefficientBy() on the class to perform the
operation.
Differential Revision: https://reviews.llvm.org/D87700
Use +/-Inf or +/-Largest as neutral element for nnan fmin/fmax
reductions. This avoids dropping any FMF flags. Preserving the
nnan flag in particular is important to get a good lowering on X86.
Differential Revision: https://reviews.llvm.org/D87586
If we're multiplying all elements of a vector by '0' or '1' then we can more efficiently perform this as a clearing mask (that is likely to further simplify to a shuffle blend).
This was noticed when reviewing D87502 but seems to help idiv/irem by constant cases even more as '0'/'1' values are often used for 'passthrough' cases.
Differential Revision: https://reviews.llvm.org/D88225
This is a fix for PR47630. The regression is caused by the D78011. After
this change the code starts to call the `emitGlobalConstantLargeInt` even
for constants which requires eight bytes to store.
Differential revision: https://reviews.llvm.org/D88261
This is like FastMathFlagGuard in IR. Since we use SDAG instance to get
values, it's with SelectionDAG. By creating a FlagInserter in current
scope, all values created by getNode will get the flags if no Flags
argument provided.
In this patch, I applied it to floating point operations folding part in
DAG combiner, and removed Flags passing to getNode to show its effect.
Other places in DAG combiner and other helper methods similar to getNode
also need this. They can be done in follow-up patches.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D87361
Following on from D87757 "[SplitKit] Only copy live lanes", in
SplitEditor::addDeadDef, when we're checking whether the parent live
interval has a subrange defining the same lanes, tolerate the case
where the parent subrange defines a superset of the lanes. This can
happen when the child subrange comes from SplitEditor::buildCopy
decomposing a partial copy into a sequence of subreg copies that cover
the required lanes.
Differential Revision: https://reviews.llvm.org/D88020
On failing to find a VCTP in the list of instructions that explicitly
predicate the entry of a VPT block, inspect whether the block is
controlled via VPT which is implicitly predicated due to it's
predicated operand(s).
Differential Revision: https://reviews.llvm.org/D87819
This change adds an option to basic block sections to allow cold
clusters to be assigned a custom text prefix. With a custom prefix such
as ".text.split." (D87840), lld can place them in a separate output section.
The benefits are -
* Empirically shown to improve icache and itlb metrics by 3-5%
(absolute) compared to placing split parts in .text.unlikely.
* Mitigates against poor profiles, eg samplePGO profiles used with the
machine function splitter. Optimizations such as hugepage remapping can
make different decisions at the section granularity.
* Enables section granularity hotness monitoring (checking on the
decisions made during compilation vs sample data from production).
Differential Revision: https://reviews.llvm.org/D87813
Until then, this one line fix removes the assert fail with basic block sections
with debug info. Bug tracking this: #47549
This fix does not generate loc list or DW_AT_const_value if the argument is
mentioned in a different section than the start of the function.
Temporarily fixes bugzilla : https://bugs.llvm.org/show_bug.cgi?id=47549
Differential Revision: https://reviews.llvm.org/D87787
When processing PHI nodes after a callbr, we need to make sure that the
PHI nodes on the default branch are resolved after the callbr
(inserted after INLINEASM_BR). The PHI node values on the indirect
branches are processed before the INLINEASM_BR.
Differential Revision: https://reviews.llvm.org/D86260
