When the return value is not used (i.e. only care about the value in the memory), x86 does not have to use add to implement these. Instead, it can use add, sub, inc, dec instructions with the "lock" prefix.
This is currently implemented using a bit of instruction selection trick. The issue is the target independent pattern produces one output and a chain and we want to map it into one that just output a chain. The current trick is to select it into a merge_values with the first definition being an implicit_def. The proper solution is to add new ISD opcodes for the no-output variant. DAG combiner can then transform the node before it gets to target node selection.
Problem #2 is we are adding a whole bunch of x86 atomic instructions when in fact these instructions are identical to the non-lock versions. We need a way to add target specific information to target nodes and have this information carried over to machine instructions. Asm printer (or JIT) can use this information to add the "lock" prefix.
llvm-svn: 77582
a Twine, e.g., for names).
- I am a little ambivalent about this; we don't want the string conversion of
utostr, but using overload '+' mixed with string and integer arguments is
sketchy. On the other hand, this particular usage is something of an idiom.
llvm-svn: 77579
and convert code to using it, instead of having lots of things
poke the isLookupPtrRegClass() method directly.
2. Make PointerLikeRegClass contain a 'kind' int, and store it in
the existing regclass field of TargetOperandInfo when the
isLookupPtrRegClass() predicate is set. Make getRegClass pass
this into TargetRegisterInfo::getPointerRegClass(), allowing
targets to have multiple ptr_rc things.
llvm-svn: 77504
wide vectors. Likewise, change VSTn intrinsics to take separate arguments
for each vector in a multi-vector struct. Adjust tests accordingly.
llvm-svn: 77468
- Provides static constructors for doing number to string conversions without
using temporaries.
- There are several ways to do this, I think given the Twine constraints this
is the simplest one.
- One FIXME for fast number -> hex conversion.
- Added another comment on one last major bit of perf work Twines need, which
is to make raw_svector_ostream more efficient.
llvm-svn: 77445
Devang Patel