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This completes the implementation of P1091R3 and P1381R1. This patch allow the capture of structured bindings both for C++20+ and C++17, with extension/compat warning. In addition, capturing an anonymous union member, a bitfield, or a structured binding thereof now has a better diagnostic. We only support structured bindings - as opposed to other kinds of structured statements/blocks. We still emit an error for those. In addition, support for structured bindings capture is entirely disabled in OpenMP mode as this needs more investigation - a specific diagnostic indicate the feature is not yet supported there. Note that the rest of P1091R3 (static/thread_local structured bindings) was already implemented. at the request of @shafik, i can confirm the correct behavior of lldb wit this change. Fixes https://github.com/llvm/llvm-project/issues/54300 Fixes https://github.com/llvm/llvm-project/issues/54300 Fixes https://github.com/llvm/llvm-project/issues/52720 Reviewed By: aaron.ballman Differential Revision: https://reviews.llvm.org/D122768
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! //===---------------------------------------------------------------------===//