This implicitly fixes a nasty bug in the GVN hashing (that thankfully
could only manifest as a performance bug): actually include the opcode
in the hash. The old code started the hash off with the opcode, but then
overwrote it with the type pointer.
Since this is likely to be pretty hot (GVN being already pretty
expensive) I've included a micro-optimization to just not bother with
the varargs hashing if they aren't present. I can't measure any change
in GVN performance due to this, even with a big test case like Duncan's
sqlite one. Everything I see is in the noise floor. That said, this
closes a loop hole for a potential scaling problem due to collisions if
the opcode were the differentiating aspect of the expression.
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hashing infrastructure. I wonder why we don't just use StringMap here,
and I may revisit the issue if I have time, but for now I'm just trying
to consolidate.
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complains about the truncation of a 64-bit constant to a 32-bit value
when size_t is 32-bits wide, but *only with static_cast*!!! The exact
signal that should *silence* such a warning, and in fact does silence it
with both GCC and Clang.
Anyways, this was causing grief for all the MSVC builds, so pointless
change made. Thanks to Nikola on IRC for confirming that this works.
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The first def of a virtual register cannot also read the register.
Assert on such bad machine code instead of trying to fix it.
TwoAddressInstructionPass should never create code like that.
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We are already setting <undef> flags, and that is good enough. The
<imp-def> operands don't mean anything any more.
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MachineOperands that define part of a virtual register must have an
<undef> flag if they are not intended as read-modify-write operands.
The old trick of adding an <imp-def> operand doesn't work any longer.
Fixes PR12177.
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equalities into phi node operands for which the equality is known to
hold in the incoming basic block. That's because replaceAllDominatedUsesWith
wasn't handling phi nodes correctly in general (that this didn't give wrong
results was just luck: the specific way GVN uses replaceAllDominatedUsesWith
precluded wrong changes to phi nodes).
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new hash_value infrastructure, and replace their implementations using
hash_combine. This removes a complete copy of Jenkin's lookup3 hash
function (which is both significantly slower and lower quality than the
one implemented in hash_combine) along with a somewhat scary xor-only
hash function.
Now that APInt and APFloat can be passed directly to hash_combine,
simplify the rest of the LLVMContextImpl hashing to use the new
infrastructure.
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Some BBs can become dead after codegen preparation. If we delete them here, it
could help enable tail-call optimizations later on.
<rdar://problem/10256573>
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- Shrink the opcode field to 16 bits.
- Shrink the AsmVariantID field to 8 bits.
- Store the mnemonic string in a string table, store a 16 bit index.
- Store a pascal-style length byte in the string instead of a null terminator,
so we can avoid calling strlen on every entry we visit during mnemonic search.
Shrinks X86AsmParser.o from 434k to 201k on x86_64 and eliminates relocs from the table.
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This could probably be made a lot smarter, but this is a common case and doesn't require LVI to scan a lot
of code. With this change CVP can optimize away the "shift == 0" case in Hashing.h that only gets hit when
"shift" is in a range not containing 0.
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The optimizer should handle this eventually, but currently LVI isn't really designed for this kind of stuff.
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folks who know something about PPC tell me that the byte swap is crazy
fast and without this the bit mixture would actually be different. It
might not be worse, but I've not measured it and so I'd rather not trust
it. This way, the algorithm is identical on both endianness hosts. I'll
look into any performance issues etc stemming from this.
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just ensure that the number of bytes in the pair is the sum of the bytes
in each side of the pair. As long as thats true, there are no extra
bytes that might be padding.
Also add a few tests that previously would have slipped through the
checking. The more accurate checking mechanism catches these and ensures
they are handled conservatively correctly.
Thanks to Duncan for prodding me to do this right and more simply.
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This change replaces getTypeStoreSize with getTypeAllocSize in AddressSanitizer
instrumentation for stack allocations.
One case where old behaviour produced undesired results is an optimization in
InstCombine pass (PromoteCastOfAllocation), which can replace alloca(T) with
alloca(S), where S has the same AllocSize, but a smaller StoreSize. Another
case is memcpy(long double => long double), where ASan will poison bytes 10-15
of a stack-allocated long double (StoreSize 10, AllocSize 16,
sizeof(long double) = 16).
See http://llvm.org/bugs/show_bug.cgi?id=12047 for more context.
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hashable data. This matters when we have pair<T*, U*> as a key, which is
quite common in DenseMap, etc. To that end, we need to detect when this
is safe. The requirements on a generic std::pair<T, U> are:
1) Both T and U must satisfy the existing is_hashable_data trait. Note
that this includes the requirement that T and U have no internal
padding bits or other bits not contributing directly to equality.
2) The alignment constraints of std::pair<T, U> do not require padding
between consecutive objects.
3) The alignment constraints of U and the size of T do not conspire to
require padding between the first and second elements.
Grow two somewhat magical traits to detect this by forming a pod
structure and inspecting offset artifacts on it. Hopefully this won't
cause any compilers to panic.
Added and adjusted tests now that pairs, even nested pairs, are treated
as just sequences of data.
Thanks to Jeffrey Yasskin for helping me sort through this and reviewing
the somewhat subtle traits.
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