MachineInstr::isIdenticalTo has a lot of logic for dealing with register
Defs (i.e. deciding whether to take them into account or ignore them).
This logic gets things wrong in some obscure cases, for instance if an
operand is not a Def for both the current MI and the one we are
comparing to.
I'm not sure if it's possible for this to happen for regular register
operands, but it may happen in the ARM backend for special operands
which use sentinel values for the register (i.e. 0, which is neither a
physical register nor a virtual one).
This causes MachineInstrExpressionTrait::isEqual (which uses
MachineInstr::isIdenticalTo) to return true for the following
instructions, which are the same except for the fact that one sets the
flags and the other one doesn't:
%1114 = ADDrsi %1113, %216, 17, 14, _, def _
%1115 = ADDrsi %1113, %216, 17, 14, _, _
OTOH, MachineInstrExpressionTrait::getHashValue returns different values
for the 2 instructions due to the different isDef on the last operand.
In practice this means that when trying to add those instructions to a
DenseMap, they will be considered different because of their different
hash values, but when growing the map we might get an assertion while
copying from the old buckets to the new buckets because isEqual
misleadingly returns true.
This patch makes sure that isEqual and getHashValue agree, by improving
the checks in MachineInstr::isIdenticalTo when we are ignoring virtual
register definitions (which is what the Trait uses). Firstly, instead of
checking isPhysicalRegister, we use !isVirtualRegister, so that we cover
both physical registers and sentinel values. Secondly, instead of
checking MachineOperand::isReg, we use MachineOperand::isIdenticalTo,
which checks isReg, isSubReg and isDef, which are the same values that
the hash function uses to compute the hash.
Note that the function is symmetric with this change, since if the
current operand is not a Def, we check MachineOperand::isIdenticalTo,
which returns false if the operands have different isDef's.
Differential Revision: https://reviews.llvm.org/D38789
llvm-svn: 315579
Adds MVT::ElementCount to represent the length of a
vector which may be scalable, then adds helper functions
that work with it.
Patch by Graham Hunter.
Differential Revision: https://reviews.llvm.org/D32019
llvm-svn: 300842
Remove all ilist_iterator to pointer casts. There were two reasons for
casts:
- Checking for an uninitialized (i.e., null) iterator. I added
MachineInstrBundleIterator::isValid() to check for that case.
- Comparing an iterator against the underlying pointer value while
avoiding converting the pointer value to an iterator. This is
occasionally necessary in MachineInstrBundleIterator, since there is
an assertion in the constructors that the underlying MachineInstr is
not bundled (but we don't care about that if we're just checking for
pointer equality).
To support the latter case, I rewrote the == and != operators for
ilist_iterator and MachineInstrBundleIterator.
- The implicit constructors now use enable_if to exclude
const-iterator => non-const-iterator conversions from overload
resolution (previously it was a compiler error on instantiation, now
it's SFINAE).
- The == and != operators are now global (friends), and are not
templated.
- MachineInstrBundleIterator has overloads to compare against both
const_pointer and const_reference. This avoids the implicit
conversions to MachineInstrBundleIterator that assert, instead just
checking the address (and I added unit tests to confirm this).
Notably, the only remaining uses of ilist_iterator::getNodePtrUnchecked
are in ilist.h, and no code outside of ilist*.h directly relies on this
UB end-iterator-to-pointer conversion anymore. It's still needed for
ilist_*sentinel_traits, but I'll clean that up soon.
llvm-svn: 278478
Diana Picus