arsenm added inline comments.
================ Comment at: llvm/include/llvm/IR/Intrinsics.td:903-907 +// Load of a value provided by the system library at a fixed address. Used for +// accessing things like HWCAP word provided by GLIBC. +def int_fixed_addr_ld + : DefaultAttrsIntrinsic<[llvm_i32_ty], [llvm_i32_ty], + [IntrInaccessibleMemOnly, ImmArg<ArgIndex<0>>]>; ---------------- nemanjai wrote: > arsenm wrote: > > From this description I don't understand what this is supposed to do. What > > does the input mean? Why does this use an i32 immarg and not a pointer? Why > > is the result only i32? > That is fair enough. The description is fairly vague. I can try to improve it > as per below. The parameter for this is not a pointer (i.e. not an address). > It is an immediate that represents the index into the enumeration of values > that are provided at a fixed address. The back end is then free to produce > the actual fixed address and the load itself. > The choice for the result type was admittedly arbitrary - on PPC, the values > provided by GLIBC are 32-bit words. > > Proposed comment describing this intrinsic: > ``` > // This intrinsic is provided to allow back ends to emit load > // instructions that load a value from a fixed address. The > // parameter to the intrinsic is not an address, but an > // immediate index into an enumeration that contains the > // union of all such values available on all back ends. > // An example is the HWCAP/HWCAP2/CPUID words > // provided by GLIBC on PowerPC to allow fast access > // to commonly used parts of AUXV. These are provided > // at a fixed offset into the TCB (accessible through the > // thread pointer). > ``` This is baking an a very target specific implementation of device identification. Could you redefine this as something more abstract? Like returns a device ID integer, or a bool that some int input is supported? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D152914/new/ https://reviews.llvm.org/D152914 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
