the processor keeps a return addresses stack (RAS) which stores the address
and the instruction execution state of the instruction after a function-call
type branch instruction.
Calling a "noreturn" function with normal call instructions (e.g. bl) can
corrupt RAS and causes 100% return misprediction so LLVM should use a
unconditional branch instead. i.e.
mov lr, pc
b _foo
The "mov lr, pc" is issued in order to get proper backtrace.
rdar://8979299
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with a vector condition); such selects become VSELECT codegen nodes.
This patch also removes VSETCC codegen nodes, unifying them with SETCC
nodes (codegen was actually often using SETCC for vector SETCC already).
This ensures that various DAG combiner optimizations kick in for vector
comparisons. Passes dragonegg bootstrap with no testsuite regressions
(nightly testsuite as well as "make check-all"). Patch mostly by
Nadav Rotem.
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support for the case where alignment<value size.
These cases were silently miscompiled before this patch.
Now they are overly verbose -especially storing is- and
any front-end should still avoid misaligned memory
accesses as much as possible. The bit juggling algorithm
added here probably has some room for improvement still.
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Before the implementation of isLegalAddressingMode, some rare cases
of code were miscompiled if optimized with the LoopStrengthReduce pass.
It is unclear (to me) if LSR is "allowed" to produce wrong code with a
bad TargetLowering, or if the bug is elsewhere and this patch just
hides it.
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for an "i" constraint should get lowered; PR 6309. While
this argument was passed around a lot, this is the only
place it was used, so it goes away from a lot of other
places.
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const_casts, and it reinforces the design of the Target classes being
immutable.
SelectionDAGISel::IsLegalToFold is now a static member function, because
PIC16 uses it in an unconventional way. There is more room for API
cleanup here.
And PIC16's AsmPrinter no longer uses TargetLowering.
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Target independent isel should always pass along the "tail call" property. Change
target hook LowerCall's parameter "isTailCall" into a refernce. If the target
decides it's impossible to honor the tail call request, it should set isTailCall
to false to make target independent isel happy.
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Instead of awkwardly encoding calling-convention information with ISD::CALL,
ISD::FORMAL_ARGUMENTS, ISD::RET, and ISD::ARG_FLAGS nodes, TargetLowering
provides three virtual functions for targets to override:
LowerFormalArguments, LowerCall, and LowerRet, which replace the custom
lowering done on the special nodes. They provide the same information, but
in a more immediately usable format.
This also reworks much of the target-independent tail call logic. The
decision of whether or not to perform a tail call is now cleanly split
between target-independent portions, and the target dependent portion
in IsEligibleForTailCallOptimization.
This also synchronizes all in-tree targets, to help enable future
refactoring and feature work.
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Small refactoring in LowerFORMAL_ARGUMENTS().
Correct minor formatting issues.
Remove size argument of CreateCopyOfByValArgument().
Remove dead argument from CalculateStackSlotSize().
Remove unused variable ReturnAddrIndex from various targets.
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have the alignment be calculated up front, and have the back-ends obey whatever
alignment is decided upon.
This allows for future work that would allow for precise no-op placement and the
like.
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- Fix fabs, fneg for f32 and f64.
- Use BuildVectorSDNode.isConstantSplat, now that the functionality exists
- Continue to improve i64 constant lowering. Lower certain special constants
to the constant pool when they correspond to SPU's shufb instruction's
special mask values. This avoids the overhead of performing a shuffle on a
zero-filled vector just to get the special constant when the memory load
suffices.
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- Rename fcmp.ll test to fcmp32.ll, start adding new double tests to fcmp64.ll
- Fix select_bits.ll test
- Capitulate to the DAGCombiner and move i64 constant loads to instruction
selection (SPUISelDAGtoDAG.cpp).
<rant>DAGCombiner will insert all kinds of 64-bit optimizations after
operation legalization occurs and now we have to do most of the work that
instruction selection should be doing twice (once to determine if v2i64
build_vector can be handled by SelectCode(), which then runs all of the
predicates a second time to select the necessary instructions.) But,
CellSPU is a good citizen.</rant>
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- Ensure that (operation) legalization emits proper FDIV libcall when needed.
- Fix various bugs encountered during llvm-spu-gcc build, along with various
cleanups.
- Start supporting double precision comparisons for remaining libgcc2 build.
Discovered interesting DAGCombiner feature, which is currently solved via
custom lowering (64-bit constants are not legal on CellSPU, but DAGCombiner
insists on inserting one anyway.)
- Update README.
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sequences in SPUDAGToDAGISel.cpp and SPU64InstrInfo.td, killing custom
DAG node types as needed.
- i64 mul is now a legal instruction, but emits an instruction sequence
that stretches tblgen and the imagination, as well as violating laws of
several small countries and most southern US states (just kidding, but
looking at a function with 80+ parameters is really weird and just plain
wrong.)
- Update tests as needed.
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- Add preliminary support for v2i32; load/store generates the right code but
there's a lot work to be done to make this vector type operational.
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promote from i1 all the way up to the canonical SetCC type.
In order to discover an appropriate type to use, pass
MVT::Other to getSetCCResultType. In order to be able to
do this, change getSetCCResultType to take a type as an
argument, not a value (this is also more logical).
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instruction sequence and cannot ordinarily be simplified by DAGcombine
into the various target description files or SPUDAGToDAGISel.cpp.
This makes some 64-bit operations legal.
- Eliminate target-dependent ISD enums.
- Update tests.
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DAGcombine's ability to find reasons to remove truncates when they were not
needed. Consequently, the CellSPU backend would produce correct, but _really
slow and horrible_, code.
Replaced with instruction sequences that do the equivalent truncation in
SPUInstrInfo.td.
- Re-examine how unaligned loads and stores work. Generated unaligned
load code has been tested on the CellSPU hardware; see the i32operations.c
and i64operations.c in CodeGen/CellSPU/useful-harnesses. (While they may be
toy test code, it does prove that some real world code does compile
correctly.)
- Fix truncating stores in bug 3193 (note: unpack_df.ll will still make llc
fault because i64 ult is not yet implemented.)
- Added i64 eq and neq for setcc and select/setcc; started new instruction
information file for them in SPU64InstrInfo.td. Additional i64 operations
should be added to this file and not to SPUInstrInfo.td.
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- First patch from Nehal Desai, a new contributor at Aerospace. Nehal's patch
fixes sign/zero/any-extending loads for integers and floating point. Example
code, compiled w/o debugging or optimization where he first noticed the bug:
int main(void) {
float a = 99.0;
printf("%d\n", a);
return 0;
}
Verified that this code actually works on a Cell SPU.
Changes by Scott Michel:
- Fix bug in the value type list constructed by SPUISD::LDRESULT to include
both the load result's result and chain, not just the chain alone.
- Simplify LowerLOAD and remove extraneous and unnecessary chains.
- Remove unused SPUISD pseudo instructions.
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ReplaceNodeResults: rather than returning a node which
must have the same number of results as the original
node (which means mucking around with MERGE_VALUES,
and which is also easy to get wrong since SelectionDAG
folding may mean you don't get the node you expect),
return the results in a vector.
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(a) Improve the extract element code: there's no need to do gymnastics with
rotates into the preferred slot if a shuffle will do the same thing.
(b) Rename a couple of SPUISD pseudo-instructions for readability and better
semantic correspondence.
(c) Fix i64 sign/any/zero extension lowering.
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and add a TargetLowering hook for it to use to determine when this
is legal (i.e. not in PIC mode, etc.)
This allows instruction selection to emit folded constant offsets
in more cases, such as the included testcase, eliminating the need
for explicit arithmetic instructions.
This eliminates the need for the C++ code in X86ISelDAGToDAG.cpp
that attempted to achieve the same effect, but wasn't as effective.
Also, fix handling of offsets in GlobalAddressSDNodes in several
places, including changing GlobalAddressSDNode's offset from
int to int64_t.
The Mips, Alpha, Sparc, and CellSPU targets appear to be
unaware of GlobalAddress offsets currently, so set the hook to
false on those targets.
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and better control the abstraction. Rename the type
to MVT. To update out-of-tree patches, the main
thing to do is to rename MVT::ValueType to MVT, and
rewrite expressions like MVT::getSizeInBits(VT) in
the form VT.getSizeInBits(). Use VT.getSimpleVT()
to extract a MVT::SimpleValueType for use in switch
statements (you will get an assert failure if VT is
an extended value type - these shouldn't exist after
type legalization).
This results in a small speedup of codegen and no
new testsuite failures (x86-64 linux).
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issue is operand promotion for setcc/select... but looks like the fundamental
stuff is implemented for CellSPU.
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