On Fri, 2024-01-05 at 17:57 +0800, chenglulu wrote:
>
> 在 2024/1/5 下午4:37, Xi Ruoyao 写道:
> > On Fri, 2024-01-05 at 11:40 +0800, Lulu Cheng wrote:
> > > bool
> > > loongarch_explicit_relocs_p (enum loongarch_symbol_type type)
> > > {
> > > + /* Instructions pcalau12i, addi.d, lu32i.d and lu52i.d must be
> > > adjancent
> > > + so that the linker can infer the PC of pcalau12i to apply
> > > relocations
> > > + to lu32i.d and lu52i.d. Otherwise, the results would be incorrect
> > > if
> > > + these four instructions are not in the same 4KiB page.
> > > + Therefore, macro instructions are used when cmodel=extreme. */
> > > + if (loongarch_symbol_extreme_p (type))
> > > + return false;
> > I think this is a bit of strange. With -mexplicit-relocs={auto,always}
> > we should still use explicit relocs, but coding all 4 instructions
> > altogether as
> >
> > "pcalau12i.d\t%1,%pc64_hi12(%2)\n\taddi.d\t%0,$r0,%pclo12(%2)\n\tlu32i.d\t%0,%pc64_lo20(%2)\n\tlu52i.d\t%0,%0,%pc64_hi12(%2)"
> >
> > Give me several hours trying to implement this...
> >
> I think there is no difference between macros and these instructions put
> together. If implement it in a split form, I think I can try it through
> TARGET_SCHED_MACRO_FUSION_PAIR_P
There is a difference:
int x;
int t() { return x; }
pcalau12i.d t0, %pc_hi20(x)
addi.d t1, r0, %pc_lo12(x)
lu32i.d t1, %pc64_lo20(x)
lu52i.d t1, t1, %pc64_hi12(x)
ldx.w a0, t0, t1
is slightly better than
pcalau12i.d t0, %pc_hi20(x)
addi.d t1, r0, %pc_lo12(x)
lu32i.d t1, %pc64_lo20(x)
lu52i.d t1, t1, %pc64_hi12(x)
addi.d t0, t0, t1
ld.w a0, t0, 0
And generating macros when -mexplicit-relocs=always can puzzle people
(it says "always" :-\ ).
--
Xi Ruoyao <[email protected]>
School of Aerospace Science and Technology, Xidian University
