In #74514 and #74778 we marked various instrumentation-added sections as
large. This causes an extra PT_LOAD segment if using the small code
model. Since people using the small code model presumably aren't hitting
relocation limits, disable this when using the small code model to avoid
the extra segment.
This uses Module::getCodeModel() which isn't necessarily reliable since
it reads module metadata (which right now only the clang frontend sets),
but it would be nice to get to a point where we reliably put this sort
of information (e.g. PIC/code model/etc) in the IR. This requires
duplicating the existing tests since opt/llc currently don't set these
metadata. If we get to a point where they do set the code model metadata
based on command line arguments then we can deduplicate these tests.
We'd like to make various instrprof globals large to make them not
contribute to relocation pressure since there are no direct accesses
to them in the module.
Similar to what was done for asan_globals in #74514.
This affects the __llvm_prf_vals, __llvm_prf_vnds, and __llvm_prf_names
sections.
The reland fixes platform.ll.
We'd like to make various instrprof globals large to make them not
contribute to relocation pressure since there are no direct accesses
to them in the module.
Similar to what was done for asan_globals in #74514.
This affects the __llvm_prf_vals, __llvm_prf_vnds, and __llvm_prf_names
sections.
`instrprof` currently does not set `__llvm_prf_vnds`'s alignment after creating it. The consequence is that the alignment is set to 16 later (c0f3ac1d00/llvm/lib/IR/DataLayout.cpp (L1019)). This can lead to undefined behaviour when we calculate `NumVNodes` in `lprofGetLoadModuleSignature` (c0f3ac1d00/compiler-rt/lib/profile/InstrProfilingMerge.c (L32)). The reason is that when the `__llvm_prf_vnds` array is 16 byte aligned, `__llvm_profile_end_vnodes() - __llvm_profile_begin_vnodes()` may not be a multiple of the size of ValueProfNode (which is 24, 20 on 32 bit targets).
This patch sets `__llvm_prf_vnds`'s alignment to its ABI alignment, which always divides its size. Then `__llvm_profile_end_vnodes() - __llvm_profile_begin_vnodes()` will be a multiple of `sizeof(ValueProfNode)`.
Reviewed By: w2yehia, MaskRay
Differential Revision: https://reviews.llvm.org/D144302
