courbet added a comment.
As discussed offline, I think this should go through an RFC process.
I guess the main reservation that people will have is that this might generate
a very large number of load stores (because we don't have a good way to
generate loops here). This is not an issue for X86 because of REPMOVS, but it
would be cool to have the opinion of people familiar with other architectures.
One way to tackle this issue could be to expand existing `mem*` functions
before the DAG. This is already happening for `memcmp` in `ExpandMemcmp`, which
could be made aware of this flag. Similar approaches could be used for other
`mem*` functions. But eventually this has to be handled here as the dag itself
can call `getMemcpy()`.
Also, the current approach does not protect against current users and future
unsavvy users calling `SelectionDAG::getMemcpy` with `AlwaysAlign == false`, so
what about actually retrieving the flag //within// the function instead of
outside ? This happens e.g. in `SelectionDAG::visitMemPCpyCall()`m
`AArch64TargetLowering::LowerCall` and others.
================
Comment at: clang/test/CodeGen/freestanding-disables-libc.c:6
+
+// NOTE: Test that assembly doesn't call memcpy function in freestanding mode.
+// RUN: %clang_cc1 -triple i386-unknown-unknown -O2 -S %s -o - | grep 'memcpy'
----------------
That's the responsibility of LLVM, so this test should be in
`llvm/test/Codegen`.
================
Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:6093
+ assert(MF->getFunction().getParent()->getModuleFlag("force-inline-libc") ==
+ nullptr);
----------------
Please add an error message (maybe "modules with 'force-inline-libc' should
never emit library calls")
================
Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5483
+static bool IsForceInlineLibc(const SelectionDAG &DAG) {
+ const Module *M = DAG.getMachineFunction().getFunction().getParent();
----------------
isForceInlineLibc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D60719/new/
https://reviews.llvm.org/D60719
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