replacement of multiple values. This is slightly more efficient
than doing multiple ReplaceAllUsesOfValueWith calls, and theoretically
could be optimized even further. However, an important property of this
new function is that it handles the case where the source value set and
destination value set overlap. This makes it feasible for isel to use
SelectNodeTo in many very common cases, which is advantageous because
SelectNodeTo avoids a temporary node and it doesn't require CSEMap
updates for users of values that don't change position.
Revamp MorphNodeTo, which is what does all the work of SelectNodeTo, to
handle operand lists more efficiently, and to correctly handle a number
of corner cases to which its new wider use exposes it.
This commit also includes a change to the encoding of post-isel opcodes
in SDNodes; now instead of being sandwiched between the target-independent
pre-isel opcodes and the target-dependent pre-isel opcodes, post-isel
opcodes are now represented as negative values. This makes it possible
to test if an opcode is pre-isel or post-isel without having to know
the size of the current target's post-isel instruction set.
These changes speed up llc overall by 3% and reduce memory usage by 10%
on the InstructionCombining.cpp testcase with -fast and -regalloc=local.
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of all sizes from i1 to i256. The code is not
always that great, for example (x86)
movw %di, %ax
movw %ax, i17_s
where the store could be directly from %di.
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sizes from i1 to i256. The generated code is
like one huge bug report of things that the DAG
combiner fails to simplify!
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simply does the atomic.cmp.swap on the larger type,
which means it blows away whatever is sitting in
the bytes just after the memory location, i.e.
causes a buffer overflow. This really requires
target specific code, which is why LegalizeTypes
doesn't try to handle this case generically. The
existing (wrong) code in LegalizeDAG will go away
automatically once the type legalization code is
removed from LegalizeDAG so I'm leaving it there
for the moment. Meanwhile, don't test for this
feature.
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allowed to canonicalize return values).
Add a test that checks if return value and function attributes are not removed.
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return values that are still (partially) live. Instead of updating all uses of
a call instruction after removing some elements, it now just rebuilds the
original struct (With undef gaps where the unused values were) and leaves it to
instcombine to clean this up.
The added testcase still fails currently, but this is due to instcombine which
isn't good enough yet. I will fix that part next.
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In LegalizeDAG the value is zero-extended to
the new type before byte swapping. It doesn't
matter how the extension is done since the new
bits are shifted off anyway after the swap, so
extend by any old rubbish bits. This results
in the final assembler for the testcase being
one line shorter.
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the second half of link-global-to-func.ll and causes some minor changes in
messages.
There are two TODOs here. First, this causes a regression in
2008-07-06-AliasWeakDest.ll, which is now failing (so I xfailed it). Anton,
I would really appreciate it if you could take a look at this. It should be
a matter of adding proper alias support to GetLinkageResult, and was probably
already a latent bug that would manifest with globals.
The second todo is to reimplement LinkAlias in the same pattern as
function and global linking. This should be pretty straight-forward for
someone who knows aliases, but isn't a requirement for correctness.
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(replacing a function with a global). This is needed when building
llvm itself with LTO on darwin, because of the EXPLICIT_SYMBOL hack
in lib/system/DynamicLibrary.cpp.
Implementation of linking the other way will need to wait for a
cleanup of LinkFunctionProtos.
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8 %reg1024<def> = IMPLICIT_DEF
12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2
The live range [12, 14) are not part of the r1024 live interval since it's defined by an implicit def. It will not conflicts with live interval of r1025. Now suppose both registers are spilled, you can easily see a situation where both registers are reloaded before the INSERT_SUBREG and both target registers that would overlap.
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was using the algorithm for folding unsigned comparisons which is
completely wrong. This has been broken since the signless types change.
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This cause a regression in InstCombine/JavaCompare, which was doing the right
thing on accident. To handle the missed case, generalize the comparisons based
on masked bits a little bit to handle comparisons against the max value. For
example, we can now xform (slt i32 (and X, 4), 4) -> (setne i32 (and X, 4), 4)
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Rewrite the DeadArgumentElimination pass, to use a more explicit tracking of
dependencies between return values and/or arguments. Also make the handling of
arguments and return values the same.
The pass now looks properly inside returned structs, but only at the first
level (ie, not inside nested structs).
This version fixed a few more bugs and was cleaned up a bit. It now passes all
of LLVM's testing, and should still pass SPEC2006. There is still a minor bug
with regard to returning nested structs. Since there is currently nothing that
emits such IR, I will fix that in a seperate commit (partly because it requires
a non-trivial fix).
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