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This reverts commit r189320. Alexey Samsonov and Dmitry Vyukov presented some arguments for keeping these around - though it still seems like those tasks could be solved by a tool just using the symbol table. In a very small number of cases, thunks may be inlined & debug info might be able to save profilers & similar tools from misclassifying those cases as part of the caller. The extra changes here plumb through the VarDecl for various cases to CodeGenFunction - this provides better fidelity through a few APIs but generally just causes the CGF::StartFunction to fallback to using the name of the IR function as the name in the debug info. The changes to debug-info-global-ctor-dtor.cpp seem like goodness. The two names that go missing (in favor of only emitting those names as linkage names) are names that can be demangled - emitting them only as the linkage name should encourage tools to do just that. Again, thanks to Dinesh Dwivedi for investigation/work on this issue. llvm-svn: 189421
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! //===---------------------------------------------------------------------===//