This patch implements the new LibCallSimplifier class as outlined in [1].
In addition to providing the new base library simplification infrastructure,
all the fortified library call simplifications were moved over to the new
infrastructure. The rest of the library simplification optimizations will
be moved over with follow up patches.
NOTE: The original fortified library call simplifier located in the
SimplifyFortifiedLibCalls class was not removed because it is still
used by CodeGenPrepare. This class will eventually go away too.
[1] http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-August/052283.html
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It is possible that the live range of the value being pruned loops back
into the kill MBB where the search started. When that happens, make sure
that the beginning of KillMBB is also pruned.
Instead of starting a DFS at KillMBB and skipping the root of the
search, start a DFS at each KillMBB successor, and allow the search to
loop back to KillMBB.
This fixes PR14078.
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type coercion code, especially when targetting ARM. Things like [1
x i32] instead of i32 are very common there.
The goal of this logic is to ensure that when we are picking an alloca
type, we look through such wrapper aggregates and across any zero-length
aggregate elements to find the simplest type possible to form a type
partition.
This logic should (generally speaking) rarely fire. It only ends up
kicking in when an alloca is accessed using two different types (for
instance, i32 and float), and the underlying alloca type has wrapper
aggregates around it. I noticed a significant amount of this occurring
looking at stepanov_abstraction generated code for arm, and suspect it
happens elsewhere as well.
Note that this doesn't yet address truly heinous IR productions such as
PR14059 is concerning. Those result in mismatched *sizes* of types in
addition to mismatched access and alloca types.
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help the dragonegg builders, and no test case at this point, but this
was one dimly plausible case I spotted by inspection. Hopefully will get
a testcase from those bots soon-ish, and will tidy this up with proper
testing.
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X86 doesn't have i8 cmovs so isel would emit a branch. Emitting branches at this
level is often not a good idea because it's too late for many optimizations to
kick in. This solution doesn't add any extensions (truncs are free) and tries
to avoid introducing partial register stalls by filtering direct copyfromregs.
I'm seeing a ~10% speedup on reading a random .png file with libpng15 via
graphicsmagick on x86_64/westmere, but YMMV depending on the microarchitecture.
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are single value types, the load and store should be directly based upon
the alloca and then bitcasting can fix the type as needed afterward.
This might in theory improve some of the IR coming out of SROA, but
I don't expect big changes yet and don't have any test cases on hand.
This is really just a cleanup/refactoring patch. The next patch will
cause this code path to be hit a lot more, actually get SROA to promote
more allocas and include several more test cases.
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the interface between the front-end and the MC layer when parsing inline
assembly. Unfortunately, this is too deep into the parsing stack. Specifically,
we're unable to handle target-independent assembly (i.e., assembly directives,
labels, etc.). Note the MatchAndEmitInstruction() isn't the correct
abstraction either. I'll be exposing target-independent hooks shortly, so this
is really just a cleanup.
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local frame causes problem.
For example:
void f(StructToPass s) {
g(&s, sizeof(s));
}
will cause problem with tail-call since part of s is passed via registers and
saved in f's local frame. When g tries to access s, part of s may be corrupted
since f's local frame is popped out before the tail-call.
The current fix is to disable tail-call if getVarArgsRegSaveSize is not 0 for
the caller. This is a conservative approach, if we can prove the address of
s or part of s is not taken and passed to g, it should be okay to perform
tail-call.
rdar://12442472
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Completely update one interval at a time instead of collecting live
range fragments to be updated. This avoids building data structures,
except for a single SmallPtrSet of updated intervals.
Also share code between handleMove() and handleMoveIntoBundle().
Add support for moving dead defs across other live values in the
interval. The MI scheduler can do that.
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PHIElimination inserts IMPLICIT_DEF instructions to guarantee that all
PHI predecessors have a live-out value. These IMPLICIT_DEF values are
not considered to be real interference when coalescing virtual
registers:
%vreg1 = IMPLICIT_DEF
%vreg2 = MOV32r0
When joining %vreg1 and %vreg2, the IMPLICIT_DEF instruction and its
value number should simply be erased since the %vreg2 value number now
provides a live-out value for the PHI predecesor block.
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This is a temporary hack until Bill's project to record command line options
in the LLVM IR is ready. Clang currently sets a default CPU but that isn't
recorded anywhere and it doesn't get used in the final LTO compilation.
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On PowerPC, a bitcast of <16 x i8> to i128 may run through a code
path in ExpandRes_BITCAST that attempts to do an intermediate
bitcast to a <4 x i32> vector, and then construct the Hi and Lo parts
of the resulting i128 by pairing up two of those i32 vector elements
each. The code already recognizes that on a big-endian system, the
first two vector elements form the Hi part, and the final two vector
elements form the Lo part (vice-versa from the little-endian situation).
However, we also need to take endianness into account when forming each
of those separate pairs: on a big-endian system, vector element 0 is
the *high* part of the pair making up the Hi part of the result, and
vector element 1 is the low part of the pair. The code currently always
uses vector element 0 as the low part and vector element 1 as the high
part, as is appropriate for little-endian platforms only.
This patch fixes this by swapping the vector elements as they are
paired up as appropriate.
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DependenceAnalysis.cpp:1164:32: warning: implicit truncation from 'int' to bitfield changes value from -5 to 3
[-Wconstant-conversion]
Result.DV[Level].Direction &= ~Dependence::DVEntry::GT;
^ ~~~~~~~~~~~~~~~~~~~~~~~~
Patch from Preston Briggs <preston.briggs@gmail.com>.
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not legal. However, it should use a div instruction + mul + sub if divide is
legal. The rem legalization code was missing a check and incorrectly uses a
divrem libcall even when div is legal.
rdar://12481395
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The intent of this document is to be the go-to document for anybody who
wants to write new documentation, but isn't familiar with Sphinx.
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isa<> et al. automatically infer when the cast is an upcast (including a
self-cast), so these are no longer necessary.
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Recent changes to isa<>/dyn_cast<> have made unnecessary those classof()
of the form:
static bool classof(const Foo *) { return true; }
Accordingly, remove mention of such classof() from the documentation.
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Additionally, all such cases are handled with no dynamic check.
All `classof()` of the form
class Foo {
[...]
static bool classof(const Bar *) { return true; }
[...]
}
where Foo is an ancestor of Bar are no longer necessary.
Don't write them!
Note: The exact test is `is_base_of<Foo, Bar>`, which is non-strict, so
that Foo is considered an ancestor of itself.
This leads to the following rule of thumb for LLVM-style RTTI:
The argument type of `classof()` should be a strict ancestor.
For more information about implementing LLVM-style RTTI, see
docs/HowToSetUpLLVMStyleRTTI.rst
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This classof() is effectively saying that a MachineCodeEmitter "is-a"
JITEmitter, but JITEmitter is in fact a descendant of
MachineCodeEmitter, so this is not semantically correct. Consequently,
none of the assertions that rely on these classof() actualy check
anything.
Remove the RTTI (which didn't actually check anything) and use
static_cast<> instead.
Post-Mortem Bug Analysis
========================
Cause of the bug
----------------
r55022 appears to be the source of the classof() and assertions removed
by this commit. It aimed at removing some dynamic_cast<> that were
solely in the assertions. A typical diff hunk from that commit looked
like:
- assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
- JITEmitter *JE = static_cast<JITEmitter*>(getCodeEmitter());
+ assert(isa<JITEmitter>(MCE) && "Unexpected MCE?");
+ JITEmitter *JE = cast<JITEmitter>(getCodeEmitter());
Hence, the source of the bug then seems to be an attempt to replace
dynamic_cast<> with LLVM-style RTTI without properly setting up the
class hierarchy for LLVM-style RTTI. The bug therefore appears to be
simply a "thinko".
What initially indicated the presence of the bug
------------------------------------------------
After implementing automatic upcasting for isa<>, classof() functions of
the form
static bool classof(const Foo *) { return true; }
were removed, since they only serve the purpose of optimizing
statically-OK upcasts. A subsequent recompilation triggered a build
failure on the isa<> tests within the removed asserts, since the
automatic upcasting (correctly) failed to substitute this classof().
Key to pinning down the root cause of the bug
---------------------------------------------
After being alerted to the presence of the bug, some thought about the
semantics which were being asserted by the buggy classof() revealed that
it was incorrect.
How the bug could have been prevented
-------------------------------------
This bug could have been prevented by better documentation for how to
set up LLVM-style RTTI. This should be solved by the recently added
documentation HowToSetUpLLVMStyleRTTI. However, this bug suggests that
the documentation should clearly explain the contract that classof()
must fulfill. The HowToSetUpLLVMStyleRTTI already explains this
contract, but it is a little tucked away. A future patch will expand
that explanation and make it more prominent.
There does not appear to be a simple way to have the compiler prevent
this bug, since fundamentally it boiled down to a spurious classof()
where the programmer made an erroneous statement about the conversion.
This suggests that perhaps the interface to LLVM-style RTTI of classof()
is not the best. There is already some evidence for this, since in a
number of places Clang has classof() forward to classofKind(Kind K)
which evaluates the cast in terms of just the Kind. This could probably
be generalized to simply a `static const Kind MyKind;` field in leaf
classes and `static const Kind firstMyKind, lastMyKind;` for non-leaf
classes, and have the rest of the work be done inside Casting.h,
assuming that the Kind enum is laid out in a preorder traversal of the
inheritance tree.
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When all cases of a switch statement are dead, the weights vector only has one
element, and we will get an ssertion failure when calling createBranchWeights.
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