rui314/mold
1
1
Fork 0
mirror of https://github.com/rui314/mold.git synced 2024-10-04 08:37:28 +03:00
Code Issues Projects Releases Wiki Activity

[Mach-O] Improve LOH_ARM64_ADRP_LDR_GOT_LDR

Browse Source
This commit is contained in:
Rui Ueyama 2022-07-28 16:35:58 +08:00
parent 08cf940a7a
commit 12f941c58d
2 changed files with 45 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
macho/arch-arm64.cc
View File

@ -470,6 +470,17 @@ void RangeExtensionThunk<E>::copy_buf(Context<E> &ctx) {
#define ASSERT_RANGE(val, start, size) \
assert((start) <= (val) && (val) < ((start) + (size)))
static u32 to_ldr_immediate(u32 insn) {
switch (insn & 0xffc0'0000) {
case 0xf940'0000: // ldr X1, [X0]
return 0x5800'0000 | bits(insn, 4, 0); // ldr X1, imm
case 0xb940'0000: // ldr W1, [X0]
return 0x1800'0000 | bits(insn, 4, 0); // ldr W1, imm
default:
return 0;
}
}
// On ARM, we generally need two or more instructions to materialize
// an address of an object in a register or jump to a function.
// However, if an object or a function is close enough to PC, a single
@ -524,22 +535,13 @@ void apply_linker_optimization_hints(Context<E> &ctx) {
ul32 *loc2 = (ul32 *)(loc + offset2);
ul32 *loc3 = (ul32 *)(loc + offset3);
// We expect the following instructions:
// We expect the following instructions for a GOT-indirect load:
//
// adrp Rx, _foo@GOTPAGE
// ldr Ry, [Rx, _foo@GOTPAGEOFF]
// ldr Rz/Wz, [Ry]
i64 size = 0;
// adrp X1, _foo@GOTPAGE
// ldr X2, [X1, _foo@GOTPAGEOFF]
// ldr/ldrb/ldrsb/ldrsh/... X3/W3, [X2]
if ((*loc1 & 0x9f00'0000) != 0x9000'0000 ||
(*loc2 & 0xbfc0'0000) != 0xb940'0000)
break;
if (u32 val = (*loc3 & 0xffc0'0000); val == 0xf940'0000)
size = 8;
else if (val == 0xb940'0000)
size = 4;
else
(*loc2 & 0xffc0'0000) != 0xf940'0000)
break;
u64 got_addr = page(subsec->get_addr(ctx) + offset1) +
@ -551,22 +553,27 @@ void apply_linker_optimization_hints(Context<E> &ctx) {
u64 got_value = *(ul64 *)(ctx.buf + ctx.got.hdr.offset + got_addr -
ctx.got.hdr.addr);
// If the GOT slot is already filled with a value and we can
// inline the value, do it.
if (got_value) {
i64 disp = got_value - subsec->get_addr(ctx) - offset3;
if (disp == sign_extend(disp, 20)) {
// If the GOT entry has already been filled, and its value is
// within the range of LDR, we can convert to
//
// nop
// nop
// ldr Rz/Wz, _foo
*loc1 = 0xd503'201f;
*loc2 = 0xd503'201f;
*loc3 = (size == 8 ? 0x5800'0000 : 0x1800'0000) |
(bits(disp, 20, 2) << 5) | bits(*loc3, 4, 0);
u32 insn = to_ldr_immediate(*loc3);
if (disp == sign_extend(disp, 20) && insn) {
*loc1 = 0xd503'201f; // nop
*loc2 = 0xd503'201f; // nop
*loc3 = insn | (bits(disp, 20, 2) << 5); // ldr X3/W3, [_foo]
break;
}
}
// If the GOT slot is close enough to PC, we can eliminate ADRP.
if (i64 disp = got_addr - subsec->get_addr(ctx) - offset2;
disp == sign_extend(disp, 20)) {
u32 insn = 0x5800'0000 | bits(*loc2, 4, 0);
*loc1 = 0xd503'201f; // nop
*loc2 = insn | (bits(disp, 20, 2) << 5); // ldr X2, _foo@GOT
}
break;
}
case LOH_ARM64_ADRP_ADD: {
@ -590,8 +597,8 @@ void apply_linker_optimization_hints(Context<E> &ctx) {
// We expect the following instructions:
//
// adrp reg1, _foo@PAGE
// add reg2, reg1, _foo@PAGEOFF
// adrp X1, _foo@PAGE
// add X2, X1, _foo@PAGEOFF
if ((*loc1 & 0x9f00'0000) != 0x9000'0000 ||
(*loc2 & 0xffc0'0000) != 0x9100'0000)
break;
@ -604,7 +611,7 @@ void apply_linker_optimization_hints(Context<E> &ctx) {
if (disp == sign_extend(disp, 20)) {
// Rewrite it with
// nop
// adr reg2, _foo
// adr X2, _foo
*loc1 = 0xd503'201f;
*loc2 = 0x1000'0000 | (bits(disp, 1, 0) << 29) |
(bits(disp, 20, 2) << 5) | bits(*loc2, 4, 0);

16
test/macho/linker-optimization-hints.sh
View File

@ -15,8 +15,10 @@ mkdir -p $t
cat <<EOF | $CC -o $t/a.o -c -xc - -O2
#include <stdio.h>
int foo = -1;
long bar = -1;
char x1 = -1;
short x2 = -1;
int x3 = -1;
long x4 = -1;
void hello() {
printf("Hello world ");
@ -28,16 +30,18 @@ cat <<EOF | $CC -o $t/b.o -c -xc - -O2
void hello();
extern int foo;
extern long bar;
extern char x1;
extern short x2;
extern int x3;
extern long x4;
int main() {
hello();
printf("%d %ld\n", foo, bar);
printf("%d %d %d %ld\n", x1, x2, x3, x4);
}
EOF
clang --ld-path=./ld64 -o $t/exe $t/a.o $t/b.o
$t/exe | grep -q 'Hello world -1 -1'
$t/exe | grep -q 'Hello world -1 -1 -1 -1'
echo OK