There is no reason to do this: it's a scratch register and can therefore
hold any arbitrary value. And because it is in an interrupt, this code
is performance critical so it should be as short as possible.
I believe r0 was cleared because of the following:
1. There used to be a bug that the cleared register was r0, not r1 as
it should have been.
2. This was fixed in https://reviews.llvm.org/D99467, but left the code
to clear r0.
This patch completes D99467 by removing the `clr r0` instruction.
Differential Revision: https://reviews.llvm.org/D116756
I have matched the RISCV backend, which only uses the interrupt save
list in getCalleeSavedRegs, _not_ in getCallPreservedMask. I don't know
the details of these two methods, but with it, the correct amount of
registers is saved and restored.
Without this patch, practically all interrupt handlers that call a
function will miscompile.
I have added a test to verify this behavior. I've also added a very
simple test to verify that more normal interrupt operations (in this
case, incrementing a global value) behave as expected.
Differential Revision: https://reviews.llvm.org/D116551
The r1 register should be cleared in prologue of ISR as it is used
as constant zero.
Reviewed By: dylanmckay
Differential Revision: https://reviews.llvm.org/D99467
This patch fixes a corruption of the stack pointer and several registers in any AVR interrupt with non-empty stack frame. Previously, the callee-saved registers were popped before restoring the stack pointer, causing the pointer math to use the wrong base value while also corrupting the caller's register. This change fixes the code to restore the stack pointer last before exiting the interrupt service routine.
https://bugs.llvm.org/show_bug.cgi?id=47253
Reviewed By: dylanmckay
Differential Revision: https://reviews.llvm.org/D87735
Patch by Andrew Dona-Couch.
In the past, AVR functions were only lowered with interrupt-specific
machine code if the function was defined with the "avr-interrupt" or
"avr-signal" calling conventions.
This patch modifies the backend so that if the function does not have a
special calling convention, but does have an "interrupt" attribute,
that function is interpreted as a function with interrupts.
This also extracts the "is this function an interrupt" logic from
several disparate places in the backend into one AVRMachineFunctionInfo
attribute.
Bug found by Wilhelm Meier.
Summary:
A lot of the pseudo instructions are required because LLVM assumes that
all integers of the same size as the pointer size are legal. This means
that it will not currently expand 16-bit instructions to their 8-bit
variants because it thinks 16-bit types are legal for the operations.
This also adds all of the CodeGen tests that required the pass to run.
Reviewers: arsenm, kparzysz
Subscribers: wdng, mgorny, modocache, llvm-commits
Differential Revision: https://reviews.llvm.org/D26577
llvm-svn: 287162
Ayke van Laethem