Cranelift emits AbsoluteRelocation Reloc::Abs8 when is_pic setting is enabled in architecture aarch64
Steps to Reproduce
(module
;; Recursive factorial
(func (export "fac-rec") (param i64) (result i64)
(if (result i64) (i64.eq (local.get 0) (i64.const 0))
(then (i64.const 1))
(else
(i64.mul (local.get 0) (call 0 (i64.sub (local.get 0) (i64.const 1))))
)
)
)
)$ wasmtime wasm2obj fac.wat fac.o
Code emitted fac.o has absolute relocations.
Expected Results
Is expected for Cranelift to emit a relative relocation for aarch64 when is_pic is enabled.
Actual Results
Code emitted with an absolute relocation.
Versions and Environment
Cranelift version: cranelift-codegen = "0.73.0"
Operating system: Any
Architecture: Aarch64
Extra info
Here's where the wrong code is emitted:
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&Inst::LoadExtName { |
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rd, |
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ref name, |
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offset, |
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} => { |
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let inst = Inst::ULoad64 { |
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rd, |
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mem: AMode::Label(MemLabel::PCRel(8)), |
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flags: MemFlags::trusted(), |
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}; |
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inst.emit(sink, emit_info, state); |
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let inst = Inst::Jump { |
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dest: BranchTarget::ResolvedOffset(12), |
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}; |
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inst.emit(sink, emit_info, state); |
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let srcloc = state.cur_srcloc(); |
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sink.add_reloc(srcloc, Reloc::Abs8, name, offset); |
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if emit_info.flags().emit_all_ones_funcaddrs() { |
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sink.put8(u64::max_value()); |
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} else { |
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sink.put8(0); |
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} |
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} |
In the new x86 backend however, the is_pic case is properly handled:
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Inst::LoadExtName { dst, name, offset } => { |
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if info.flags().is_pic() { |
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// Generates: movq symbol@GOTPCREL(%rip), %dst |
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let enc_dst = int_reg_enc(dst.to_reg()); |
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sink.put1(0x48 | ((enc_dst >> 3) & 1) << 2); |
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sink.put1(0x8B); |
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sink.put1(0x05 | ((enc_dst & 7) << 3)); |
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emit_reloc(sink, state, Reloc::X86GOTPCRel4, name, -4); |
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sink.put4(0); |
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// Offset in the relocation above applies to the address of the *GOT entry*, not |
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// the loaded address; so we emit a separate add or sub instruction if needed. |
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if *offset < 0 { |
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assert!(*offset >= -i32::MAX as i64); |
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sink.put1(0x48 | ((enc_dst >> 3) & 1)); |
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sink.put1(0x81); |
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sink.put1(0xe8 | (enc_dst & 7)); |
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sink.put4((-*offset) as u32); |
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} else if *offset > 0 { |
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assert!(*offset <= i32::MAX as i64); |
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sink.put1(0x48 | ((enc_dst >> 3) & 1)); |
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sink.put1(0x81); |
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sink.put1(0xc0 | (enc_dst & 7)); |
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sink.put4(*offset as u32); |
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} |
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} else { |
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// The full address can be encoded in the register, with a relocation. |
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// Generates: movabsq $name, %dst |
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let enc_dst = int_reg_enc(dst.to_reg()); |
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sink.put1(0x48 | ((enc_dst >> 3) & 1)); |
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sink.put1(0xB8 | (enc_dst & 7)); |
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emit_reloc(sink, state, Reloc::Abs8, name, *offset); |
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if info.flags().emit_all_ones_funcaddrs() { |
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sink.put8(u64::max_value()); |
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} else { |
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sink.put8(0); |
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} |
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} |
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} |