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docs/StackMaps.rst
| Show First 20 Lines • Show All 323 Lines • ▼ Show 20 Lines | Header { | ||||
| uint16 : Reserved (expected to be 0) | uint16 : Reserved (expected to be 0) | ||||
| } | } | ||||
| uint32 : NumFunctions | uint32 : NumFunctions | ||||
| uint32 : NumConstants | uint32 : NumConstants | ||||
| uint32 : NumRecords | uint32 : NumRecords | ||||
| StkSizeRecord[NumFunctions] { | StkSizeRecord[NumFunctions] { | ||||
| uint64 : Function Address | uint64 : Function Address | ||||
| uint64 : Stack Size | uint64 : Stack Size | ||||
| uint64 : Record Count | |||||
| } | } | ||||
| Constants[NumConstants] { | Constants[NumConstants] { | ||||
| uint64 : LargeConstant | uint64 : LargeConstant | ||||
| } | } | ||||
| StkMapRecord[NumRecords] { | StkMapRecord[NumRecords] { | ||||
| uint64 : PatchPoint ID | uint64 : PatchPoint ID | ||||
| uint32 : Instruction Offset | uint32 : Instruction Offset | ||||
| uint16 : Reserved (record flags) | uint16 : Reserved (record flags) | ||||
| ▲ Show 20 Lines • Show All 89 Lines • ▼ Show 20 Lines | |||||
| Stack Map Usage | Stack Map Usage | ||||
| =============== | =============== | ||||
| The stack map support described in this document can be used to | The stack map support described in this document can be used to | ||||
| precisely determine the location of values at a specific position in | precisely determine the location of values at a specific position in | ||||
| the code. LLVM does not maintain any mapping between those values and | the code. LLVM does not maintain any mapping between those values and | ||||
| any higher-level entity. The runtime must be able to interpret the | any higher-level entity. The runtime must be able to interpret the | ||||
| stack map record given only the ID, offset, and the order of the | stack map record given only the ID, offset, and the order of the | ||||
| locations, which LLVM preserves. | locations, records, and functions, which LLVM preserves. | ||||
| Note that this is quite different from the goal of debug information, | Note that this is quite different from the goal of debug information, | ||||
| which is a best-effort attempt to track the location of named | which is a best-effort attempt to track the location of named | ||||
| variables at every instruction. | variables at every instruction. | ||||
| An important motivation for this design is to allow a runtime to | An important motivation for this design is to allow a runtime to | ||||
| commandeer a stack frame when execution reaches an instruction address | commandeer a stack frame when execution reaches an instruction address | ||||
| associated with a stack map. The runtime must be able to rebuild a | associated with a stack map. The runtime must be able to rebuild a | ||||
| ▲ Show 20 Lines • Show All 57 Lines • ▼ Show 20 Lines | |||||
| Supported Architectures | Supported Architectures | ||||
| ======================= | ======================= | ||||
| Support for StackMap generation and the related intrinsics requires | Support for StackMap generation and the related intrinsics requires | ||||
| some code for each backend. Today, only a subset of LLVM's backends | some code for each backend. Today, only a subset of LLVM's backends | ||||
| are supported. The currently supported architectures are X86_64, | are supported. The currently supported architectures are X86_64, | ||||
| PowerPC, and Aarch64. | PowerPC, and Aarch64. | ||||