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4c006e557d
"Add a completed/incomplete type difference. This allows us to have
partial types for contexts and forward decls while allowing us to
complete types later on for debug purposes.
This piggy-backs on the metadata replacement and rauw changes
for temporary nodes and takes advantage of the incremental
support I added in earlier. This allows us to, if we decide,
to limit adding methods and variables to structures in order
to limit the amount of debug information output into a .o file.
The caching is a bit complicated though so any thoughts on
untangling that are welcome."
with a fix:
- Remove all RAUW during type construction by adding stub versions
of types that we later complete.
and some TODOs:
- Add an RAUW cache for forward declared types so that we can replace
them at the end of compilation.
- Remove the code that updates on completed types because we no
longer need to have that happen. We emit incomplete types on
purpose and only want to know when we want to complete them.
llvm-svn: 150752
IRgen optimization opportunities. //===---------------------------------------------------------------------===// The common pattern of -- short x; // or char, etc (x == 10) -- generates an zext/sext of x which can easily be avoided. //===---------------------------------------------------------------------===// Bitfields accesses can be shifted to simplify masking and sign extension. For example, if the bitfield width is 8 and it is appropriately aligned then is is a lot shorter to just load the char directly. //===---------------------------------------------------------------------===// It may be worth avoiding creation of alloca's for formal arguments for the common situation where the argument is never written to or has its address taken. The idea would be to begin generating code by using the argument directly and if its address is taken or it is stored to then generate the alloca and patch up the existing code. In theory, the same optimization could be a win for block local variables as long as the declaration dominates all statements in the block. NOTE: The main case we care about this for is for -O0 -g compile time performance, and in that scenario we will need to emit the alloca anyway currently to emit proper debug info. So this is blocked by being able to emit debug information which refers to an LLVM temporary, not an alloca. //===---------------------------------------------------------------------===// We should try and avoid generating basic blocks which only contain jumps. At -O0, this penalizes us all the way from IRgen (malloc & instruction overhead), all the way down through code generation and assembly time. On 176.gcc:expr.ll, it looks like over 12% of basic blocks are just direct branches! //===---------------------------------------------------------------------===//