https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119894
Bug ID: 119894
Summary: -fno-PIC -Os on loongarch creates code incompatible
with plts
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: phcoder at gmail dot com
Target Milestone: ---
Created attachment 61170
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61170&action=edit
Test program
When compiling test program (attached) as loongarch64-linux-gnu-gcc -Os -g
-shared -o misc.so misc.c -nostdlib -fno-PIC. We get the following code:
364: 57ff8fff bl -116 # 2f0 <grub_divmod64@plt>
/home/phcoder/grub-extras/misc.c:50
368: 28c0206c ld.d $t0, $sp, 8
36c: 02c005ef addi.d $t3, $t3, 1
So gcc relies on grub_divmod64@plt to preserve $t3. $t3 is preserved in
generated code of grub_divmod64 but insertion of PLT by the linker throws
things off as plt has following code:
2f0: 1c00010f pcaddu12i $t3, 8
2f4: 28f441ef ld.d $t3, $t3, -752
2f8: 4c0001ed jirl $t1, $t3, 0
As per ABI specification $t3 is caller-preserved so gcc needs to take insertion
of PLTs into account when reusing the registers.
