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Auto merge of #86416 - Amanieu:asm_clobber_only, r=nagisa
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Add clobber-only register classes for asm!

These are needed to properly express a function call ABI using a clobber
list, even though we don't support passing actual values into/out of
these registers.
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@bors
bors committed Jul 11, 2021
2 parents dfd7b8d + d2a1d04 commit 99f8efe
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Showing 11 changed files with 270 additions and 59 deletions.
16 changes: 16 additions & 0 deletions compiler/rustc_ast_lowering/src/asm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
);

// Some register classes can only be used as clobbers. This
// means that we disallow passing a value in/out of the asm and
// require that the operand name an explicit register, not a
// register class.
if reg_class.is_clobber_only(asm_arch.unwrap())
&& !(is_clobber && matches!(reg, asm::InlineAsmRegOrRegClass::Reg(_)))
{
let msg = format!(
"register class `{}` can only be used as a clobber, \
not as an input or output",
reg_class.name()
);
sess.struct_span_err(op_sp, &msg).emit();
continue;
}

if !is_clobber {
// Validate register classes against currently enabled target
// features. We check that at least one type is available for
Expand Down
50 changes: 49 additions & 1 deletion compiler/rustc_codegen_llvm/src/asm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
let mut clobbers = vec![];
let mut output_types = vec![];
let mut op_idx = FxHashMap::default();
let mut clobbered_x87 = false;
for (idx, op) in operands.iter().enumerate() {
match *op {
InlineAsmOperandRef::Out { reg, late, place } => {
Expand All @@ -150,7 +151,27 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
let ty = if let Some(ref place) = place {
layout = Some(&place.layout);
llvm_fixup_output_type(self.cx, reg.reg_class(), &place.layout)
} else if !is_target_supported(reg.reg_class()) {
} else if matches!(
reg.reg_class(),
InlineAsmRegClass::X86(
X86InlineAsmRegClass::mmx_reg | X86InlineAsmRegClass::x87_reg
)
) {
// Special handling for x87/mmx registers: we always
// clobber the whole set if one register is marked as
// clobbered. This is due to the way LLVM handles the
// FP stack in inline assembly.
if !clobbered_x87 {
clobbered_x87 = true;
clobbers.push("~{st}".to_string());
for i in 1..=7 {
clobbers.push(format!("~{{st({})}}", i));
}
}
continue;
} else if !is_target_supported(reg.reg_class())
|| reg.reg_class().is_clobber_only(asm_arch)
{
// We turn discarded outputs into clobber constraints
// if the target feature needed by the register class is
// disabled. This is necessary otherwise LLVM will try
Expand Down Expand Up @@ -565,6 +586,9 @@ fn reg_to_llvm(reg: InlineAsmRegOrRegClass, layout: Option<&TyAndLayout<'tcx>>)
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::reg) => "r",
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::vreg) => "w",
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::vreg_low16) => "x",
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::preg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg) => "r",
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg_thumb) => "l",
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::sreg)
Expand All @@ -586,13 +610,19 @@ fn reg_to_llvm(reg: InlineAsmRegOrRegClass, layout: Option<&TyAndLayout<'tcx>>)
InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => "f",
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg) => "r",
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => "f",
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::vreg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg) => "r",
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg_abcd) => "Q",
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg_byte) => "q",
InlineAsmRegClass::X86(X86InlineAsmRegClass::xmm_reg)
| InlineAsmRegClass::X86(X86InlineAsmRegClass::ymm_reg) => "x",
InlineAsmRegClass::X86(X86InlineAsmRegClass::zmm_reg) => "v",
InlineAsmRegClass::X86(X86InlineAsmRegClass::kreg) => "^Yk",
InlineAsmRegClass::X86(
X86InlineAsmRegClass::x87_reg | X86InlineAsmRegClass::mmx_reg,
) => unreachable!("clobber-only"),
InlineAsmRegClass::Wasm(WasmInlineAsmRegClass::local) => "r",
InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::reg) => "r",
InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::wreg) => "w",
Expand All @@ -617,6 +647,9 @@ fn modifier_to_llvm(
| InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::vreg_low16) => {
if modifier == Some('v') { None } else { modifier }
}
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::preg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg)
| InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg_thumb) => None,
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::sreg)
Expand All @@ -639,6 +672,9 @@ fn modifier_to_llvm(
InlineAsmRegClass::PowerPC(_) => None,
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg)
| InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => None,
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::vreg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg)
| InlineAsmRegClass::X86(X86InlineAsmRegClass::reg_abcd) => match modifier {
None if arch == InlineAsmArch::X86_64 => Some('q'),
Expand All @@ -663,6 +699,9 @@ fn modifier_to_llvm(
_ => unreachable!(),
},
InlineAsmRegClass::X86(X86InlineAsmRegClass::kreg) => None,
InlineAsmRegClass::X86(X86InlineAsmRegClass::x87_reg | X86InlineAsmRegClass::mmx_reg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::Wasm(WasmInlineAsmRegClass::local) => None,
InlineAsmRegClass::Bpf(_) => None,
InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
Expand All @@ -681,6 +720,9 @@ fn dummy_output_type(cx: &CodegenCx<'ll, 'tcx>, reg: InlineAsmRegClass) -> &'ll
| InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::vreg_low16) => {
cx.type_vector(cx.type_i64(), 2)
}
InlineAsmRegClass::AArch64(AArch64InlineAsmRegClass::preg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg)
| InlineAsmRegClass::Arm(ArmInlineAsmRegClass::reg_thumb) => cx.type_i32(),
InlineAsmRegClass::Arm(ArmInlineAsmRegClass::sreg)
Expand All @@ -704,13 +746,19 @@ fn dummy_output_type(cx: &CodegenCx<'ll, 'tcx>, reg: InlineAsmRegClass) -> &'ll
InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => cx.type_f64(),
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg) => cx.type_i32(),
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => cx.type_f32(),
InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::vreg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg)
| InlineAsmRegClass::X86(X86InlineAsmRegClass::reg_abcd) => cx.type_i32(),
InlineAsmRegClass::X86(X86InlineAsmRegClass::reg_byte) => cx.type_i8(),
InlineAsmRegClass::X86(X86InlineAsmRegClass::xmm_reg)
| InlineAsmRegClass::X86(X86InlineAsmRegClass::ymm_reg)
| InlineAsmRegClass::X86(X86InlineAsmRegClass::zmm_reg) => cx.type_f32(),
InlineAsmRegClass::X86(X86InlineAsmRegClass::kreg) => cx.type_i16(),
InlineAsmRegClass::X86(X86InlineAsmRegClass::x87_reg | X86InlineAsmRegClass::mmx_reg) => {
unreachable!("clobber-only")
}
InlineAsmRegClass::Wasm(WasmInlineAsmRegClass::local) => cx.type_i32(),
InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::reg) => cx.type_i64(),
InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::wreg) => cx.type_i32(),
Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_span/src/symbol.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -756,6 +756,7 @@ symbols! {
minnumf64,
mips_target_feature,
misc,
mmx_reg,
modifiers,
module,
module_path,
Expand Down Expand Up @@ -899,6 +900,7 @@ symbols! {
prefetch_read_instruction,
prefetch_write_data,
prefetch_write_instruction,
preg,
prelude,
prelude_import,
preserves_flags,
Expand Down Expand Up @@ -1343,6 +1345,7 @@ symbols! {
wrapping_sub,
wreg,
write_bytes,
x87_reg,
xmm_reg,
ymm_reg,
zmm_reg,
Expand Down
86 changes: 54 additions & 32 deletions compiler/rustc_target/src/asm/aarch64.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ def_reg_class! {
reg,
vreg,
vreg_low16,
preg,
}
}

Expand All @@ -15,6 +16,7 @@ impl AArch64InlineAsmRegClass {
match self {
Self::reg => &['w', 'x'],
Self::vreg | Self::vreg_low16 => &['b', 'h', 's', 'd', 'q', 'v'],
Self::preg => &[],
}
}

Expand All @@ -40,13 +42,15 @@ impl AArch64InlineAsmRegClass {
128 => Some(('q', "q0")),
_ => None,
},
Self::preg => None,
}
}

pub fn default_modifier(self, _arch: InlineAsmArch) -> Option<(char, &'static str)> {
match self {
Self::reg => Some(('x', "x0")),
Self::vreg | Self::vreg_low16 => Some(('v', "v0")),
Self::preg => None,
}
}

Expand All @@ -61,6 +65,7 @@ impl AArch64InlineAsmRegClass {
VecI8(8), VecI16(4), VecI32(2), VecI64(1), VecF32(2), VecF64(1),
VecI8(16), VecI16(8), VecI32(4), VecI64(2), VecF32(4), VecF64(2);
},
Self::preg => &[],
}
}
}
Expand Down Expand Up @@ -95,38 +100,55 @@ def_regs! {
x27: reg = ["x27", "w27"],
x28: reg = ["x28", "w28"],
x30: reg = ["x30", "w30", "lr", "wlr"],
v0: vreg, vreg_low16 = ["v0", "b0", "h0", "s0", "d0", "q0"],
v1: vreg, vreg_low16 = ["v1", "b1", "h1", "s1", "d1", "q1"],
v2: vreg, vreg_low16 = ["v2", "b2", "h2", "s2", "d2", "q2"],
v3: vreg, vreg_low16 = ["v3", "b3", "h3", "s3", "d3", "q3"],
v4: vreg, vreg_low16 = ["v4", "b4", "h4", "s4", "d4", "q4"],
v5: vreg, vreg_low16 = ["v5", "b5", "h5", "s5", "d5", "q5"],
v6: vreg, vreg_low16 = ["v6", "b6", "h6", "s6", "d6", "q6"],
v7: vreg, vreg_low16 = ["v7", "b7", "h7", "s7", "d7", "q7"],
v8: vreg, vreg_low16 = ["v8", "b8", "h8", "s8", "d8", "q8"],
v9: vreg, vreg_low16 = ["v9", "b9", "h9", "s9", "d9", "q9"],
v10: vreg, vreg_low16 = ["v10", "b10", "h10", "s10", "d10", "q10"],
v11: vreg, vreg_low16 = ["v11", "b11", "h11", "s11", "d11", "q11"],
v12: vreg, vreg_low16 = ["v12", "b12", "h12", "s12", "d12", "q12"],
v13: vreg, vreg_low16 = ["v13", "b13", "h13", "s13", "d13", "q13"],
v14: vreg, vreg_low16 = ["v14", "b14", "h14", "s14", "d14", "q14"],
v15: vreg, vreg_low16 = ["v15", "b15", "h15", "s15", "d15", "q15"],
v16: vreg = ["v16", "b16", "h16", "s16", "d16", "q16"],
v17: vreg = ["v17", "b17", "h17", "s17", "d17", "q17"],
v18: vreg = ["v18", "b18", "h18", "s18", "d18", "q18"],
v19: vreg = ["v19", "b19", "h19", "s19", "d19", "q19"],
v20: vreg = ["v20", "b20", "h20", "s20", "d20", "q20"],
v21: vreg = ["v21", "b21", "h21", "s21", "d21", "q21"],
v22: vreg = ["v22", "b22", "h22", "s22", "d22", "q22"],
v23: vreg = ["v23", "b23", "h23", "s23", "d23", "q23"],
v24: vreg = ["v24", "b24", "h24", "s24", "d24", "q24"],
v25: vreg = ["v25", "b25", "h25", "s25", "d25", "q25"],
v26: vreg = ["v26", "b26", "h26", "s26", "d26", "q26"],
v27: vreg = ["v27", "b27", "h27", "s27", "d27", "q27"],
v28: vreg = ["v28", "b28", "h28", "s28", "d28", "q28"],
v29: vreg = ["v29", "b29", "h29", "s29", "d29", "q29"],
v30: vreg = ["v30", "b30", "h30", "s30", "d30", "q30"],
v31: vreg = ["v31", "b31", "h31", "s31", "d31", "q31"],
v0: vreg, vreg_low16 = ["v0", "b0", "h0", "s0", "d0", "q0", "z0"],
v1: vreg, vreg_low16 = ["v1", "b1", "h1", "s1", "d1", "q1", "z1"],
v2: vreg, vreg_low16 = ["v2", "b2", "h2", "s2", "d2", "q2", "z2"],
v3: vreg, vreg_low16 = ["v3", "b3", "h3", "s3", "d3", "q3", "z3"],
v4: vreg, vreg_low16 = ["v4", "b4", "h4", "s4", "d4", "q4", "z4"],
v5: vreg, vreg_low16 = ["v5", "b5", "h5", "s5", "d5", "q5", "z5"],
v6: vreg, vreg_low16 = ["v6", "b6", "h6", "s6", "d6", "q6", "z6"],
v7: vreg, vreg_low16 = ["v7", "b7", "h7", "s7", "d7", "q7", "z7"],
v8: vreg, vreg_low16 = ["v8", "b8", "h8", "s8", "d8", "q8", "z8"],
v9: vreg, vreg_low16 = ["v9", "b9", "h9", "s9", "d9", "q9", "z9"],
v10: vreg, vreg_low16 = ["v10", "b10", "h10", "s10", "d10", "q10", "z10"],
v11: vreg, vreg_low16 = ["v11", "b11", "h11", "s11", "d11", "q11", "z11"],
v12: vreg, vreg_low16 = ["v12", "b12", "h12", "s12", "d12", "q12", "z12"],
v13: vreg, vreg_low16 = ["v13", "b13", "h13", "s13", "d13", "q13", "z13"],
v14: vreg, vreg_low16 = ["v14", "b14", "h14", "s14", "d14", "q14", "z14"],
v15: vreg, vreg_low16 = ["v15", "b15", "h15", "s15", "d15", "q15", "z15"],
v16: vreg = ["v16", "b16", "h16", "s16", "d16", "q16", "z16"],
v17: vreg = ["v17", "b17", "h17", "s17", "d17", "q17", "z17"],
v18: vreg = ["v18", "b18", "h18", "s18", "d18", "q18", "z18"],
v19: vreg = ["v19", "b19", "h19", "s19", "d19", "q19", "z19"],
v20: vreg = ["v20", "b20", "h20", "s20", "d20", "q20", "z20"],
v21: vreg = ["v21", "b21", "h21", "s21", "d21", "q21", "z21"],
v22: vreg = ["v22", "b22", "h22", "s22", "d22", "q22", "z22"],
v23: vreg = ["v23", "b23", "h23", "s23", "d23", "q23", "z23"],
v24: vreg = ["v24", "b24", "h24", "s24", "d24", "q24", "z24"],
v25: vreg = ["v25", "b25", "h25", "s25", "d25", "q25", "z25"],
v26: vreg = ["v26", "b26", "h26", "s26", "d26", "q26", "z26"],
v27: vreg = ["v27", "b27", "h27", "s27", "d27", "q27", "z27"],
v28: vreg = ["v28", "b28", "h28", "s28", "d28", "q28", "z28"],
v29: vreg = ["v29", "b29", "h29", "s29", "d29", "q29", "z29"],
v30: vreg = ["v30", "b30", "h30", "s30", "d30", "q30", "z30"],
v31: vreg = ["v31", "b31", "h31", "s31", "d31", "q31", "z31"],
p0: preg = ["p0"],
p1: preg = ["p1"],
p2: preg = ["p2"],
p3: preg = ["p3"],
p4: preg = ["p4"],
p5: preg = ["p5"],
p6: preg = ["p6"],
p7: preg = ["p7"],
p8: preg = ["p8"],
p9: preg = ["p9"],
p10: preg = ["p10"],
p11: preg = ["p11"],
p12: preg = ["p12"],
p13: preg = ["p13"],
p14: preg = ["p14"],
p15: preg = ["p15"],
ffr: preg = ["ffr"],
#error = ["x18", "w18"] =>
"x18 is used as a reserved register on some targets and cannot be used as an operand for inline asm",
#error = ["x19", "w19"] =>
Expand Down
6 changes: 6 additions & 0 deletions compiler/rustc_target/src/asm/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -533,6 +533,12 @@ impl InlineAsmRegClass {
Self::Err => unreachable!("Use of InlineAsmRegClass::Err"),
}
}

/// Returns whether registers in this class can only be used as clobbers
/// and not as inputs/outputs.
pub fn is_clobber_only(self, arch: InlineAsmArch) -> bool {
self.supported_types(arch).is_empty()
}
}

#[derive(
Expand Down
34 changes: 34 additions & 0 deletions compiler/rustc_target/src/asm/riscv.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ def_reg_class! {
RiscV RiscVInlineAsmRegClass {
reg,
freg,
vreg,
}
}

Expand Down Expand Up @@ -44,6 +45,7 @@ impl RiscVInlineAsmRegClass {
}
}
Self::freg => types! { "f": F32; "d": F64; },
Self::vreg => &[],
}
}
}
Expand Down Expand Up @@ -120,6 +122,38 @@ def_regs! {
f29: freg = ["f29", "ft9"],
f30: freg = ["f30", "ft10"],
f31: freg = ["f31", "ft11"],
v0: vreg = ["v0"],
v1: vreg = ["v1"],
v2: vreg = ["v2"],
v3: vreg = ["v3"],
v4: vreg = ["v4"],
v5: vreg = ["v5"],
v6: vreg = ["v6"],
v7: vreg = ["v7"],
v8: vreg = ["v8"],
v9: vreg = ["v9"],
v10: vreg = ["v10"],
v11: vreg = ["v11"],
v12: vreg = ["v12"],
v13: vreg = ["v13"],
v14: vreg = ["v14"],
v15: vreg = ["v15"],
v16: vreg = ["v16"],
v17: vreg = ["v17"],
v18: vreg = ["v18"],
v19: vreg = ["v19"],
v20: vreg = ["v20"],
v21: vreg = ["v21"],
v22: vreg = ["v22"],
v23: vreg = ["v23"],
v24: vreg = ["v24"],
v25: vreg = ["v25"],
v26: vreg = ["v26"],
v27: vreg = ["v27"],
v28: vreg = ["v28"],
v29: vreg = ["v29"],
v30: vreg = ["v30"],
v31: vreg = ["v31"],
#error = ["x9", "s1"] =>
"s1 is used internally by LLVM and cannot be used as an operand for inline asm",
#error = ["x8", "s0", "fp"] =>
Expand Down
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