https://bugs.llvm.org/show_bug.cgi?id=42984
Bug ID: 42984
Summary: RISCV interrupt attribute doesn't preserve
caller-saved registers when calling functions
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: chaos2...@gmail.com
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
Created attachment 22373
--> https://bugs.llvm.org/attachment.cgi?id=22373&action=edit
Sample test case of expected behavior
There seem to be 2 cases of the interrupt attribute being tested.
1. A minimal interrupt where only the registers being used are preserved.
2. An interrupt that preserves all registers since it is making a function
call.
However, there is also the case of:
3. An interrupt that contains some logic, as well as making function calls.
It needs to preserve caller-saved registers before making function calls.
I have attached a sample test case for what I expect would happen.
Below I have included a sample c file that illustrates the behavior:
extern int foo();
extern void otherfoo();
extern int c;
__attribute__((interrupt)) void foo_with_call_interrupt(void) {
int x = foo();
otherfoo();
c = x;
}
A quick explanation of the C file.
1. I make a call to a function that returns an integer, this will now be in reg
a0.
2. I then make a call to another function, this function could have trashed reg
a0.
3. I try and use the integer returned from the first function. Reg a0 was
never preserved, so we are running off of undefined behavior.
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