diff options
Diffstat (limited to 'llvm/docs/Extensions.rst')
| -rw-r--r-- | llvm/docs/Extensions.rst | 60 |
1 files changed, 59 insertions, 1 deletions
diff --git a/llvm/docs/Extensions.rst b/llvm/docs/Extensions.rst index 89a0e80..91a3ac0 100644 --- a/llvm/docs/Extensions.rst +++ b/llvm/docs/Extensions.rst @@ -416,7 +416,36 @@ as offsets relative to prior addresses. The following versioning schemes are currently supported (newer versions support features of the older versions). -Version 3 (newest): Capable of encoding callsite offsets. Enabled by the 6th bit +Version 4 (newest): Capable of encoding basic block hashes. This feature is +enabled by the 7th bit of the feature byte. + +Example: + +.. code-block:: gas + + .section ".llvm_bb_addr_map","",@llvm_bb_addr_map + .byte 4 # version number + .byte 96 # feature byte + .quad .Lfunc_begin0 # address of the function + .byte 2 # number of basic blocks + # BB record for BB_0 + .byte 0 # BB_0 ID + .uleb128 .Lfunc_begin0-.Lfunc_begin0 # BB_0 offset relative to function entry (always zero) + .byte 0 # number of callsites in this block + .uleb128 .LBB_END0_0-.Lfunc_begin0 # BB_0 size + .byte x # BB_0 metadata + .quad 9080480745856761856 # BB_0 hash + # BB record for BB_1 + .byte 1 # BB_1 ID + .uleb128 .LBB0_1-.LBB_END0_0 # BB_1 offset relative to the end of last block (BB_0). + .byte 2 # number of callsites in this block + .uleb128 .LBB0_1_CS0-.LBB0_1 # offset of callsite end relative to the previous offset (.LBB0_1) + .uleb128 .LBB0_1_CS1-.LBB0_1_CS0 # offset of callsite end relative to the previous offset (.LBB0_1_CS0) + .uleb128 .LBB_END0_1-.LBB0_1_CS1 # BB_1 size offset (Offset of the block end relative to the previous offset). + .byte y # BB_1 metadata + .quad 2363478788702666771 # BB_1 hash + +Version 3: Capable of encoding callsite offsets. Enabled by the 6th bit of the feature byte. Example: @@ -601,6 +630,35 @@ sees fit (generally the section that would provide the best locality). .. _CFI jump table: https://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#forward-edge-cfi-for-indirect-function-calls +``SHT_LLVM_CALL_GRAPH`` Section (Call Graph) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This section is used to store the call graph. It has a type of +``SHT_LLVM_CALL_GRAPH`` (0x6fff4c0f). Details of call graph section layout +are described in :doc:`CallGraphSection`. + +For example: + +.. code-block:: gas + + .section ".llvm.callgraph","",@llvm_call_graph + .byte 0 + .byte 7 + .quad .Lball + .quad 0 + .byte 3 + .quad foo + .quad bar + .quad baz + .byte 3 + .quad 4524972987496481828 + .quad 3498816979441845844 + .quad 8646233951371320954 + +This indicates that ``ball`` calls ``foo``, ``bar`` and ``baz`` directly; +``ball`` indirectly calls functions whose types are ``4524972987496481828``, +``3498816979441845844`` and ``8646233951371320954``. + CodeView-Dependent ------------------ |