From 81027a2126d6a99685501395dc498bdc0b05eb62 Mon Sep 17 00:00:00 2001 From: Tom Stellard Date: Fri, 10 Jun 2016 00:31:13 +0000 Subject: docs: Add AMDGPU relocation information Summary: This documents the various relocation types that are supported by the Radeon Open Compute (ROC) runtime (which is essentially the dynamic linker for AMDGPU). Only R_AMDGPU_32 is not currently supported by the ROC runtime, but it will usually be resolved at link time by lld. Patch by: Konstantin Zhuravlyov Reviewers: kzhuravl, rafael Subscribers: rafael, arsenm, llvm-commits, kzhuravl Differential Revision: http://reviews.llvm.org/D20952 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272352 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/CodeGenerator.rst | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) (limited to 'docs/CodeGenerator.rst') diff --git a/docs/CodeGenerator.rst b/docs/CodeGenerator.rst index 5a55b0cabc9..e8753b92643 100644 --- a/docs/CodeGenerator.rst +++ b/docs/CodeGenerator.rst @@ -2643,3 +2643,54 @@ of a program is limited to 4K instructions: this ensures fast termination and a limited number of kernel function calls. Prior to running an eBPF program, a verifier performs static analysis to prevent loops in the code and to ensure valid register usage and operand types. + +The AMDGPU backend +------------------ + +The AMDGPU code generator lives in the lib/Target/AMDGPU directory, and is an +open source native AMD GCN ISA code generator. + +Target triples supported +^^^^^^^^^^^^^^^^^^^^^^^^ + +The following are the known target triples that are supported by the AMDGPU +backend. + +* **amdgcn--** --- AMD GCN GPUs (AMDGPU.7.0.0+) +* **amdgcn--amdhsa** --- AMD GCN GPUs (AMDGPU.7.0.0+) with HSA support +* **r600--** --- AMD GPUs HD2XXX-HD6XXX + +Relocations +^^^^^^^^^^^ + +Supported relocatable fields are: + +* **word32** --- This specifies a 32-bit field occupying 4 bytes with arbitrary + byte alignment. These values use the same byte order as other word values in + the AMD GPU architecture +* **word64** --- This specifies a 64-bit field occupying 8 bytes with arbitrary + byte alignment. These values use the same byte order as other word values in + the AMD GPU architecture + +Following notations are used for specifying relocation types + +* **A** --- Represents the addend used to compute the value of the relocatable + field +* **S** --- Represents the value of the symbol whose index resides in the + relocation entry + +AMDGPU Backend generates *Elf64_Rela* relocation records with the following +supported relocation types: + + ==================== ===== ========== ============================ + Relocation type Value Field Calculation + ==================== ===== ========== ============================ + ``R_AMDGPU_NONE`` 0 ``none`` ``none`` + ``R_AMDGPU_32_LOW`` 1 ``word32`` (S + A) & 0xFFFFFFFF + ``R_AMDGPU_32_HIGH`` 2 ``word32`` ((S + A) >> 32) & 0xFFFFFFFF + ``R_AMDGPU_64`` 3 ``word64`` S + A + ``R_AMDGPU_32`` 4 ``word32`` S + A + ==================== ===== ========== ============================ + +Only R_AMDGPU_32_LOW and R_AMDGPU_32_HIGH can be handled by the +dynamic linker. The rest must be statically resolved. -- cgit v1.2.3