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LoongArch: apply relaxation to tls desc #1333

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Aug 21, 2024
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LoongArch: apply relaxation to tls desc #1333

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60 changes: 55 additions & 5 deletions src/arch-loongarch.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -548,7 +548,7 @@ void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
//
// pcalau12i $a0, 0
// R_LARCH_TLS_DESC_PC_HI20 foo
// addi.d $a0, $a0, 0
// addi.[dw] $a0, $a0, 0
// R_LARCH_TLS_DESC_PC_LO12 foo
// ld.d $ra, $a0, 0
// R_LARCH_TLS_DESC_LD foo
Expand All @@ -563,6 +563,14 @@ void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
// lu12i.w $a0, foo@TPOFF
// addi.w $a0, $a0, foo@TPOFF
//
// And we may relax the instructions to one instruction as following
// if its TP-relative address is small
//
// <nop>
// <nop>
// <nop>
// ori $a0, $r0, foo@TPOFF
//
// or to the following if the TP-relative address is known at
// process startup time.
//
Expand All @@ -573,11 +581,25 @@ void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
//
// Note that if section-shrinking relaxation is enabled, nop may be
// completely deleted.
//
// If we could not transform tls desc model to initial-exec/local-exec
// model. We may try relax the frist two instructions to pcaddi as
// following.
//
// pcaddi $a0, 0
// ld.d $ra, $a0, 0
// jirl $ra, $ra, 0
if (removed_bytes == 0) {
if (sym.has_tlsdesc(ctx))
write_j20(loc, hi20(sym.get_tlsdesc_addr(ctx) + A, P));
else
*(ul32 *)loc = 0x0340'0000; // nop
} else if (sym.has_tlsdesc(ctx)) {
// Rewrite pcalau12i + addi.d with pcaddi
assert(removed_bytes == 4);
*(ul32 *)loc = 0x1800'0000 | get_rd(*(ul32 *)loc); // pcaddi
write_j20(loc, (sym.get_tlsdesc_addr(ctx) + A - P) >> 2);
i += 3;
}
break;
case R_LARCH_TLS_DESC_PC_LO12:
Expand All @@ -589,7 +611,7 @@ void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
}
break;
case R_LARCH_TLS_DESC_LD:
if (sym.has_tlsdesc(ctx)) {
if (sym.has_tlsdesc(ctx) || removed_bytes == 4) {
// Do nothing
} else if (sym.has_gottp(ctx)) {
*(ul32 *)loc = 0x1a00'0004; // pcalau12i $a0, 0
Expand All @@ -609,8 +631,12 @@ void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
*(ul32 *)loc = 0x2880'0084; // ld.w $a0, $a0, 0
write_k12(loc, sym.get_gottp_addr(ctx) + A);
} else {
*(ul32 *)loc = 0x0280'0084; // addi.w $a0, $a0, 0
write_k12(loc, S + A - ctx.tp_addr);
i64 val = S + A - ctx.tp_addr;
if (val <= 0xfff)
*(ul32 *)loc = 0x0380'0004; // ori $a0, $r0, 0
else
*(ul32 *)loc = 0x0280'0084; // addi.w $a0, $a0, 0
write_k12(loc, val);
}
break;
case R_LARCH_TLS_LE_HI20_R:
Expand Down Expand Up @@ -965,11 +991,35 @@ void shrink_section(Context<E> &ctx, InputSection<E> &isec, bool use_rvc) {
delta += 4;
}
break;
case R_LARCH_TLS_DESC_PC_HI20:
case R_LARCH_TLS_DESC_PC_HI20: {
if (!sym.has_tlsdesc(ctx))
delta += 4;
else if (i + 3 < rels.size() &&
rels[i + 2].r_type == R_LARCH_TLS_DESC_PC_LO12 &&
rels[i + 2].r_offset == rels[i].r_offset + 4 &&
rels[i + 3].r_type == R_LARCH_RELAX) {
i64 dist = compute_distance(ctx, sym, isec, r);
u32 insn1 = *(ul32 *)(isec.contents.data() + rels[i].r_offset);
u32 insn2 = *(ul32 *)(isec.contents.data() + rels[i].r_offset + 4);
bool is_addi_d = (insn2 & 0xffc0'0000) == 0x02c0'0000;

if (dist % 4 == 0 && -(1 << 21) <= dist && dist < (1 << 21) &&
is_addi_d && get_rd(insn1) == get_rd(insn2) &&
get_rd(insn2) == get_rj(insn2))
delta += 4;
}
break;
}
case R_LARCH_TLS_DESC_PC_LO12:
if (!sym.has_tlsdesc(ctx))
delta += 4;
break;
case R_LARCH_TLS_DESC_LD:
if (!sym.has_tlsdesc(ctx) && !sym.has_gottp(ctx))
if (i64 val = sym.get_addr(ctx) + r.r_addend - ctx.tp_addr;
val <= 0xfff)
delta += 4;
break;
}
}

Expand Down
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