FPSCR and FPEXC will be stored in FPStatusRegs, after GPRCS2 has been
saved.
- GPRCS1
- GPRCS2
- FPStatusRegs (new)
- DPRCS
- GPRCS3
- DPRCS2
FPSCR is present on all targets with a VFP, but the FPEXC register is
not present on Cortex-M devices, so different amounts of bytes are
being pushed onto the stack depending on our target, which would
affect alignment for subsequent saves.
DPRCS1 will sum up all previous bytes that were saved, and will emit
extra instructions to ensure that its alignment is correct. My
assumption is that if DPRCS1 is able to correct its alignment to be
correct, then all subsequent saves will also have correct alignment.
Avoid annotating the saving of FPSCR and FPEXC for functions marked
with the interrupt_save_fp attribute, even though this is done as part
of frame setup. Since these are status registers, there really is no
viable way of annotating this. Since these aren't GPRs or DPRs, they
can't be used with .save or .vsave directives. Instead, just record
that the intermediate registers r4 and r5 are saved to the stack
again.
Co-authored-by: Jake Vossen <jake@vossen.dev>
Co-authored-by: Alan Phipps <a-phipps@ti.com>
[clang][ARM] Fix warning for using VFP from interrupts.
This warning has three issues:
- The interrupt attribute causes the function to return using an
exception
return instruction. This warning allows calls from one function with
the interrupt attribute to another, and the diagnostic text suggests
that not having the attribute on the callee is a problem. Actually
making such a call will lead to a double exception return, which is
unpredictable according to the ARM architecture manual section
B9.1.1, "Restrictions on exception return instructions". Even on
machines where an exception return from user/system mode is
tolerated, if the callee's interrupt type is anything other than a
supervisor call or secure monitor call, it will also return to a
different address than a normal function would. For example,
returning from an "IRQ" handler will return to lr - 4, which will
generally result in calling the same function again.
- The interrupt attribute currently does not cause caller-saved VFP
registers to be saved and restored if they are used, so putting
__attribute__((interrupt)) on a called function doesn't prevent it
from clobbering VFP state.
- It is part of the -Wextra diagnostic group and can't be individually
disabled when using -Wextra, which also means the diagnostic text of
this specific warning appears in the documentation of -Wextra.
This change addresses all three issues by instead generating a warning
for any interrupt handler where the vfp feature is enabled. The warning
is
also given its own diagnostic group.
Closes#34876.
[clang][ARM] Emit an error when an interrupt handler is called.
Closes#95359.
A significant number of our tests in C accidentally use functions
without prototypes. This patch converts the function signatures to have
a prototype for the situations where the test is not specific to K&R C
declarations. e.g.,
void func();
becomes
void func(void);
This is the first batch of tests being updated (there are a significant
number of other tests left to be updated).
Summary:
When the function is compiled with soft-float or on CPU with no FPU, we
don't need to diagnose for a call from an ISR to a regular function.
Reviewers: jroelofs, eli.friedman
Reviewed By: jroelofs
Subscribers: aemerson, rengolin, javed.absar, cfe-commits
Differential Revision: https://reviews.llvm.org/D32918
llvm-svn: 302274
The idea for this originated from a really tricky bug: ISRs on ARM don't
automatically save off the VFP regs, so if say, memcpy gets interrupted and the
ISR itself calls memcpy, the regs are left clobbered when the ISR is done.
https://reviews.llvm.org/D28820
llvm-svn: 292375
The ARM-specific C attributes (currently just interrupt) need to check
for both the big- and little-endian versions of the triples, so that
they are accepted for both big and little endian targets.
TargetWindows and TargetMicrosoftCXXABI also only use the little-endian
triples, but this is correct as windows is not supported on big-endian
ARM targets (and this is asserted in lib/Basic/Targets.cpp).
Differential Revision: https://reviews.llvm.org/D24245
llvm-svn: 281596
This attribute allows users to use a modified C or C++ function as an ARM
exception-handling function and, with care, to successfully return control to
user-space after the issue has been dealt with.
rdar://problem/14207019
llvm-svn: 191769
