Some targets (e.g. PPC and Hexagon) already did this. I think it's best
to do this consistently so that frontend authors don't run into
inconsistent results when they emit `naked` functions. For example, in
Zig, we had to change our emit code to also set `frame-pointer=none` to
get reliable results across targets.
Note: I don't have commit access.
MachineFunction's probably should not include a backreference to
the owning MachineModuleInfo. Most of these references were used
just to query the MCContext, which MachineFunction already directly
stores. Other contexts are using it to query the LLVMContext, which
can already be accessed through the IR function reference.
This PR fixes the following failure by adjusting the calculation of
maximum displacement from Stack Pointer.
`LLVM ERROR: Error while trying to spill R5D from class ADDR64Bit:
Cannot scavenge register without an emergency spill slot!
`
https://github.com/llvm/llvm-project/pull/79940 put calls to
recomputeLiveIns into
a loop, to repeatedly call the function until the computation converges.
However,
this repeats a lot of code. This changes moves the loop into a function
to simplify
the handling.
Note that this changes the order in which recomputeLiveIns is called.
For example,
```
bool anyChange = false;
do {
anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
} while (anyChange);
```
only begins to recompute the live-ins for LoopMBB after the computation
for ExitMBB
has converged. With this change, all basic blocks have a recomputation
of the live-ins
for each loop iteration. This can result in less or more calls,
depending on the
situation.
On SystemZ, the outgoing argument area which is big enough for all calls
in the function is created once during the prolog, as opposed to
adjusting the stack around each call. The call-sequence instructions are
therefore not really useful any more than to compute the maximum call
frame size, which has so far been done by PEI, but can just as well be
done at an earlier point.
This patch removes the mapping of the CallFrameSetupOpcode and
CallFrameDestroyOpcode and instead computes the MaxCallFrameSize
directly after instruction selection and then removes the ADJCALLSTACK
pseudos. This removes the confusing pseudos and also avoids the problem
of having to keep the call frame size accurate when creating new MBBs.
This fixes#76618 which exposed the need to maintain the call frame size
when splitting blocks (which was not done).
This is a fix for the regression seen in
https://github.com/llvm/llvm-project/pull/79498
> Currently, the way that recomputeLiveIns works is that it will
recompute the livein registers for that MachineBasicBlock but it matters
what order you call recomputeLiveIn which can result in incorrect
register allocations down the line.
Now we do not recompute the entire CFG but we do ensure that the newly
added MBB do reach convergence.
Currently, the way that recomputeLiveIns works is that it will recompute
the livein registers for that MachineBasicBlock but it matters what
order you call recomputeLiveIn which can result in incorrect register
allocations down the line.
This PR fixes that by simply recomputing the liveins for the entire CFG
until convergence is achieved. This makes it harder to introduce subtle
bugs which alter liveness.
GCC supports building individual functions with backchain using the
__attribute__((target("backchain"))) syntax, and Clang should too.
Clang translates this into the "target-features"="+backchain" attribute,
and the -mbackchain command-line option into the "backchain" attribute.
The backend currently checks only the latter; furthermore, the backchain
target feature is not defined.
Handle backchain like soft-float. Define a target feature, convert
function attribute into it in getSubtargetImpl(), and check for target
feature instead of function attribute everywhere. Add an end-to-end test
to the Clang testsuite.
This PR moves some calculation out of `LowerCall` and into
`SystemZXPLINKFrameLowering::processFunctionBeforeFrameFinalized`.
We need to make this change because LowerCall isn't invoked for
functions that don't have function calls, and it is required for some
tooling to work correctly. A function that does not make any calls is
required to allocate 32 bytes for the parameter area required by the
ABI. However, we allocate 64 bytes because this additional space is
utilized by certain tools, like the debugger.
Co-authored-by: Yusra Syeda <yusra.syeda@ibm.com>
When the stack frame extension routine is used, the contents of r3 is overwritten.
However, if r3 is live in the prologue (ie. one of the function's parameters
resides in r3), it needs to be saved. We save r3 in r0 if r0 is available
(ie. r0 is not used as temporary storage for r4), and in the corresponding
stack slot for the third parameter otherwise.
Differential Revision: https://reviews.llvm.org/D150332
Reviewed By: uweigand
When the stack frame extension routine is used, the contents of r3 is
overwritten. However, if r3 is live in the prologue (ie. one of the
function's parameters resides in r3), it needs to be saved. We save
r3 in r0 if r0 is available (ie. r0 is not used as temporary storage
for r4), and in the corresponding stack slot for the third parameter otherwise.
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D150332
With D134950, targets get notified when a virtual register is created and/or
cloned. Targets can do the needful with the delegate callback. AMDGPU propagates
the virtual register flags maintained in the target file itself. They are useful
to identify a certain type of machine operands while inserting spill stores and
reloads. Since RegAllocFast spills the physical register itself, there is no way
its virtual register can be mapped back to retrieve the flags. It can be solved
by passing the virtual register as an additional argument. This argument has no
use when the spill interfaces are called during the greedy allocator or even the
PrologEpilogInserter and can pass a null register in such cases.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D138656
This PR adds support for creating leaf functions when there are no CSRs used, no function calls are made, no stack frame is acquired, and contain no try/catch/throw statements.
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D129687
This PR moves the handling of special registers that need to be saved/restored in the prolog/epilog respectively from determineCalleeSaves to assignCalleeSavedSpillSlots. The documentation of the parent function of assignCalleeSavedSpillSlots explicitly allows the modification of the CSI hence adding the special registers (the stack pointer register, the return address register, and the entry point register) to the CSI list at that stage should be permissible.
This cleans up the code a bit and makes it so that we do not have to place registers that are not actually considered CSRs by the spec in the CSR list, which is something of a hack.
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D125044
This reverts commit 7f230feeeac8a67b335f52bd2e900a05c6098f20.
Breaks CodeGenCUDA/link-device-bitcode.cu in check-clang,
and many LLVM tests, see comments on https://reviews.llvm.org/D121169
This patch extends support for generating huge stack frames on 64-bit XPLINK by implementing the ABI-mandated call to the stack extension routine.
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D120450
By reordering the objects on the stack frame after looking at the users, a
better utilization of displacement operands will result. This means less
needed Load Address instructions for the accessing of these objects.
This is important for very large functions where otherwise small changes
could cause a lot more/less accesses go out of range.
Note: this is not yet enabled for SystemZXPLINKFrameLowering, but should be.
Review: Ulrich Weigand
Differential Revision: https://reviews.llvm.org/D115690
This reverts commit ef8206320769ad31422a803a0d6de6077fd231d2.
- It conflicts with the existing llvm::size in STLExtras, which will now
never be called.
- Calling it without llvm:: breaks C++17 compat
This flag was set in the presence of stacksave/stackrestore in order to force
a frame pointer.
This should however not be needed per the comment in MachineFrameInfo.h
stating that a a variable sized object "...is the sole condition which
prevents frame pointer elimination", and experiments have also shown that
there seems to be no effect whatsoever on code generation with ManipulatesSP.
Review: Ulrich Weigand
This patch adds support for prologue and epilogue generation for the z/OS target under the XPLINK64 ABI for functions with a stack size of less than 1048576 bytes (huge stack frames).
Reviewed By: uweigand
Differential Revision: https://reviews.llvm.org/D114457
This patch adds support for prologue and epilogue generation for
the z/OS target under the XPLINK64 ABI for functions with a stack
size of less than 1048576 bytes (huge stack frames).
Reviewed by: uweigand, Kai
Differential Revision: https://reviews.llvm.org/D114457
This PR implements the save of the XPLINK callee-saved registers
on z/OS.
Reviewed By: uweigand, Kai
Differential Revision: https://reviews.llvm.org/D111653
This patch adds class SystemZFrameLowering which is a SystemZ-specific class
detailing special registers used by calling conventions on the target.
SystemZELFFrameLowering and SystemZXPLINKFrameLowering implement this class
for ELF and XPLINK64 respectively. Previous functionality in SystemZFrameLowering
is moved to SystemZELFFrameLowering. SystemZXPLINKFrameLowering can then be
implemented in future patches.
Reviewed By: uweigand, Kai
Differential Revision: https://reviews.llvm.org/D108777
Rename ELF specific variables, making it easier to add the XPLink
variables in future patches.
Reviewed By: abhina.sreeskantharajan, Kai
Differential Revision: https://reviews.llvm.org/D98199
- New function SDValue getBackchainAddress() used by
lowerDYNAMIC_STACKALLOC() and lowerSTACKRESTORE() to properly handle the
backchain offset also with packed-stack.
- Make a common function getBackchainOffset() for the computation of the
backchain offset and use in some places (NFC).
Review: Ulrich Weigand
Differential Revision: https://reviews.llvm.org/D93171
The loop-based probing done for stack clash protection altered R1D which
corrupted the backchain value to be stored after the probing was done.
By using R0D instead for the loop exit value, R1D is not modified.
Review: Ulrich Weigand.
Differential Revision: https://reviews.llvm.org/D92803
To accommodate frame layouts that have both fixed and scalable objects
on the stack, describing a stack location or offset using a pointer + uint64_t
is not sufficient. For this reason, we've introduced the StackOffset class,
which models both the fixed- and scalable sized offsets.
The TargetFrameLowering::getFrameIndexReference is made to return a StackOffset,
so that this can be used in other interfaces, such as to eliminate frame indices
in PEI or to emit Debug locations for variables on the stack.
This patch is purely mechanical and doesn't change the behaviour of how
the result of this function is used for fixed-sized offsets. The patch adds
various checks to assert that the offset has no scalable component, as frame
offsets with a scalable component are not yet supported in various places.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D90018
