Target/Hexagon/HexagonFrameLowering.cpp

47 //        SP during function's                 FP during function's     |
52 //   |   called functions   |  local objects   |  local objects  |FP|
62 //   ble using the SP, and the incoming arguments are accessible using the FP.
64 //   the FP.
73 // placed between the FP and the local objects, thus preventing the use of the
74 // FP to access the local objects. At the same time, the variable-sized objects
80 // pointer). The AP will be equal to "FP-p", where "p" is the smallest pad
86 // to the FP. In the presence of dynamic allocation and local alignment, such
87 // objects can only be accessed through the FP.
90 //                                                                FP --+
94 //   stack frame  | (aligned)           |     |  (CSR, spills, etc.)  |FP|
632     // Define CFA via an offset from the value of FP.
636     //   | FP | LR |          increasing addresses -->
639     //   +-- New FP (after allocframe)
729   // By default we want to use SP (since it's always there). FP requires
731   // Fixed and preallocated objects need FP if the distance from them to
839   unsigned SP = HRI.getStackRegister(), FP = HRI.getFrameRegister();
846   // Use FP at -O0, except when there are objects with extra alignment.
848   // which will make it impossible to use FP to access objects located
854     // so FP must be used to access them.
865   // If FP was picked, then there had better be FP.
869   // Having FP implies allocframe. Allocframe will store extra 8 bytes:
870   // FP/LR. If the base register is used to access an object across these
880   //     <local objects>     |FP/LR|    <input arguments>     addresses
883   //    SP/AP point --+      +-- FP points here (**)
885   //    this side of FP/LR
887   // (*) See LowerFormalArguments. The FP/LR is assumed to be present.
888   // (**) *FP == old-FP. FP+0..7 are the bytes of FP/LR.
890   // The lowering assumes that FP/LR is present, and so the offsets of
891   // the formal arguments start at 8. If FP/LR is not there we need to
897     FrameReg = FP;
903   // Calculate the actual offset in the instruction. If there is no FP
1018   // they can be accessed through FP. Otherwise they would have to be accessed