Currently HIP toolchain calls clang to emit bitcode then calls opt/llc for device compilation for the default -fno-gpu-rdc
case, which is unnecessary since clang is able to compile a single source file to ISA.
This patch fixes the HIP action builder and toolchain so that the default -fno-gpu-rdc can be done like a canonical
toolchain, i.e. one clang -cc1 invocation to compile source code to ISA.
This can avoid unnecessary processes to speed up the compilation, and avoid redundant LLVM passes which are
performed in clang -cc1 and opt.
Differential Revision: https://reviews.llvm.org/D81627
Summary:
The HIP toolchain invokes `llc` without an explicit opt-level, meaning
it always uses the default (-O2). This makes it impossible to use -O1,
for example. The HIP toolchain also coerces -Os/-Oz to -O2 even when
invoking opt, and it coerces -Og to -O2 rather than -O1.
Forward the opt-level to `llc` as well as `opt`, and only coerce levels
where it is required.
Subscribers: cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D70987
Yaxun (Sam) Liu