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x64: support PC-rel symbol references using the GOT when in PIC mode.

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This commit is contained in:
Chris Fallin
2021-01-07 21:59:42 -08:00
parent 8319244059
commit 3ee898cb2c
3 changed files with 82 additions and 12 deletions
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43
cranelift/codegen/src/isa/x64/inst/emit.rs
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@@ -2690,16 +2690,41 @@ pub(crate) fn emit(
}
Inst::LoadExtName { dst, name, offset } => {
// The full address can be encoded in the register, with a relocation.
// Generates: movabsq $name, %dst
let enc_dst = int_reg_enc(dst.to_reg());
sink.put1(0x48 | ((enc_dst >> 3) & 1));
sink.put1(0xB8 | (enc_dst & 7));
emit_reloc(sink, state, Reloc::Abs8, name, *offset);
if info.flags().emit_all_ones_funcaddrs() {
sink.put8(u64::max_value());
if info.flags().is_pic() {
// Generates: movq symbol@GOTPCREL(%rip), %dst
let enc_dst = int_reg_enc(dst.to_reg());
sink.put1(0x48 | ((enc_dst >> 3) & 1) << 2);
sink.put1(0x8B);
sink.put1(0x05 | ((enc_dst & 7) << 3));
emit_reloc(sink, state, Reloc::X86GOTPCRel4, name, -4);
sink.put4(0);
// Offset in the relocation above applies to the address of the *GOT entry*, not
// the loaded address; so we emit a separate add or sub instruction if needed.
if *offset < 0 {
assert!(*offset >= -i32::MAX as i64);
sink.put1(0x48 | ((enc_dst >> 3) & 1));
sink.put1(0x81);
sink.put1(0xe8 | (enc_dst & 7));
sink.put4((-*offset) as u32);
} else if *offset > 0 {
assert!(*offset <= i32::MAX as i64);
sink.put1(0x48 | ((enc_dst >> 3) & 1));
sink.put1(0x81);
sink.put1(0xc0 | (enc_dst & 7));
sink.put4(*offset as u32);
}
} else {
sink.put8(0);
// The full address can be encoded in the register, with a relocation.
// Generates: movabsq $name, %dst
let enc_dst = int_reg_enc(dst.to_reg());
sink.put1(0x48 | ((enc_dst >> 3) & 1));
sink.put1(0xB8 | (enc_dst & 7));
emit_reloc(sink, state, Reloc::Abs8, name, *offset);
if info.flags().emit_all_ones_funcaddrs() {
sink.put8(u64::max_value());
} else {
sink.put8(0);
}
}
}