https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93062
Bug ID: 93062
Summary: Failed to generate indirect branch for long branches
on risc-v
Product: gcc
Version: 9.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: adrien.sf.wu at gmail dot com
Target Milestone: ---
When compiling for RISC-V targets, if the program contains a branch across 2^19
bytes of code or more (for example, an `if` block containing 2^18
instructions), the compiler does not generate an indirect branch. This results
in an immediate overflow in JAL instruction and makes the file unlinkable.
For example,
$ riscv64-linux-gnu-gcc -O0 -c test.c -o test.o
generates the following code for the `if` branch:
$ objdump -d test.o
...
2e: 00e7d463 bge a5,a4,36 <a+0x36>
32: 8551606f j fffffffffff16886 <.L2+0xffffffffffe00000>
...
If trying to link this file, the following error is produced:
$ riscv64-linux-gnu-gcc test.o main.o
test1.o: in function `a':
test1.c:(.text+0x32): relocation truncated to fit: R_RISCV_JAL against `.L2'
collect2: error: ld returned 1 exit status
Source code of test.c:
int a(int c) {
if (c < 12345) {
#define A \
{ int d = c % 12345; \
int e = c ^ d * 12345; \
int f = c * d % e % 12345; \
c = f; }
#define B A A A A A A
#define C B B B B B B
#define D C C C C C C
#define E D D D D D D
E E E E E
}
return c;
}
