AMDGPU/MC: Add .amdgpu_lds directive
Summary:
The directive defines a symbol as an group/local memory (LDS) symbol.
LDS symbols behave similar to common symbols for the purposes of ELF,
using the processor-specific SHN_AMDGPU_LDS as section index.
It is the linker and/or runtime loader's job to "instantiate" LDS symbols
and resolve relocations that reference them.
It is not possible to initialize LDS memory (not even zero-initialize
as for .bss).
We want to be able to link together objects -- starting with relocatable
objects, but possible expanding to shared objects in the future -- that
access LDS memory in a flexible way.
LDS memory is in an address space that is entirely separate from the
address space that contains the program image (code and normal data),
so having program segments for it doesn't really make sense.
Furthermore, we want to be able to compile multiple kernels in a
compilation unit which have disjoint use of LDS memory. In that case,
we may want to place LDS symbols differently for different kernels
to save memory (LDS memory is very limited and physically private to
each kernel invocation), so we can't simply place LDS symbols in a
.lds section.
Hence this solution where LDS symbols always stay undefined.
Change-Id: I08cbc37a7c0c32f53f7b6123aa0afc91dbc1748f
Reviewers: arsenm, rampitec, t-tye, b-sumner, jsjodin
Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D61493
llvm-svn: 364296
diff --git a/llvm/tools/llvm-objcopy/ELF/Object.cpp b/llvm/tools/llvm-objcopy/ELF/Object.cpp
index c8c06f4..7042492 100644
--- a/llvm/tools/llvm-objcopy/ELF/Object.cpp
+++ b/llvm/tools/llvm-objcopy/ELF/Object.cpp
@@ -597,6 +597,11 @@
case SHN_COMMON:
return true;
}
+
+ if (Machine == EM_AMDGPU) {
+ return Index == SHN_AMDGPU_LDS;
+ }
+
if (Machine == EM_HEXAGON) {
switch (Index) {
case SHN_HEXAGON_SCOMMON:
@@ -618,21 +623,17 @@
return SHN_XINDEX;
return DefinedIn->Index;
}
- switch (ShndxType) {
- // This means that we don't have a defined section but we do need to
- // output a legitimate section index.
- case SYMBOL_SIMPLE_INDEX:
+
+ if (ShndxType == SYMBOL_SIMPLE_INDEX) {
+ // This means that we don't have a defined section but we do need to
+ // output a legitimate section index.
return SHN_UNDEF;
- case SYMBOL_ABS:
- case SYMBOL_COMMON:
- case SYMBOL_HEXAGON_SCOMMON:
- case SYMBOL_HEXAGON_SCOMMON_2:
- case SYMBOL_HEXAGON_SCOMMON_4:
- case SYMBOL_HEXAGON_SCOMMON_8:
- case SYMBOL_XINDEX:
- return static_cast<uint16_t>(ShndxType);
}
- llvm_unreachable("Symbol with invalid ShndxType encountered");
+
+ assert(ShndxType == SYMBOL_ABS || ShndxType == SYMBOL_COMMON ||
+ (ShndxType >= ELF::SHN_LOPROC && ShndxType <= ELF::SHN_HIPROC) ||
+ (ShndxType >= ELF::SHN_LOOS && ShndxType <= ELF::SHN_HIOS));
+ return static_cast<uint16_t>(ShndxType);
}
bool Symbol::isCommon() const { return getShndx() == SHN_COMMON; }