https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113233
Bug ID: 113233
Summary: LoongArch: target options from LTO objects not
respected during linking
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: yangyujie at loongson dot cn
Target Milestone: ---
Compiling LTO objects with certain target options like -march=, -msimd= have no
effect on the final linked binary, since COLLECT_GCC_OPTIONS from the "linker
GCC" driver always overrides these options.
For instance, running the following command:
$ gcc -S -o- -xc - -msimd=lasx -O3 <<< "void m2 (float *a, int n) { for (int i
= 0; i < n; i++) a[i] += 1; }" | grep vfadd
outputs SIMD instructions (as enabled by -msimd=lasx):
xvfadd.s $xr4,$xr4,$xr0
xvfadd.s $xr2,$xr2,$xr0
xvfadd.s $xr1,$xr1,$xr0
xvfadd.s $xr3,$xr3,$xr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr1,$vr1,$vr0
vfadd.s $vr0,$vr1,$vr0
However, LTO generates code according to the compiler's default config
(-msimd=none).
Running:
$ gcc -flto -c -o test.o -xc - -msimd=lasx -O3 <<< "void m2 (float *a, int n) {
for (int i = 0; i < n; i++) a[i] += 1; }"
and then:
$ gcc -S -o- -xlto test.o | grep vfadd
outputs nothing, indicating that the final code generation have LSX/LASX
disabled.
While:
$ gcc -S -o- -xlto test.o -mlasx | grep vfadd
outputs the same "vfadd" / "xvfadd" instructions as above.
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Proposed solution: implement option save/restore to enable LTO option
streaming.
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