diff options
| -rw-r--r-- | src/asm.rs | 111 | ||||
| -rw-r--r-- | tests/run/asm.rs | 27 |
2 files changed, 73 insertions, 65 deletions
diff --git a/src/asm.rs b/src/asm.rs index 7c3ed3c5ee9..2d3cde7b69e 100644 --- a/src/asm.rs +++ b/src/asm.rs @@ -18,30 +18,30 @@ use crate::type_of::LayoutGccExt; // Rust asm! and GCC Extended Asm semantics differ substantially. // -// 1. Rust asm operands go along as one list of operands. Operands themselves indicate -// if they're "in" or "out". "In" and "out" operands can interleave. One operand can be +// 1. Rust asm operands go along as one list of operands. Operands themselves indicate +// if they're "in" or "out". "In" and "out" operands can interleave. One operand can be // both "in" and "out" (`inout(reg)`). // -// GCC asm has two different lists for "in" and "out" operands. In terms of gccjit, -// this means that all "out" operands must go before "in" operands. "In" and "out" operands +// GCC asm has two different lists for "in" and "out" operands. In terms of gccjit, +// this means that all "out" operands must go before "in" operands. "In" and "out" operands // cannot interleave. // -// 2. Operand lists in both Rust and GCC are indexed. Index starts from 0. Indexes are important +// 2. Operand lists in both Rust and GCC are indexed. Index starts from 0. Indexes are important // because the asm template refers to operands by index. // // Mapping from Rust to GCC index would be 1-1 if it wasn't for... // -// 3. Clobbers. GCC has a separate list of clobbers, and clobbers don't have indexes. -// Contrary, Rust expresses clobbers through "out" operands that aren't tied to +// 3. Clobbers. GCC has a separate list of clobbers, and clobbers don't have indexes. +// Contrary, Rust expresses clobbers through "out" operands that aren't tied to // a variable (`_`), and such "clobbers" do have index. // -// 4. Furthermore, GCC Extended Asm does not support explicit register constraints -// (like `out("eax")`) directly, offering so-called "local register variables" -// as a workaround. These variables need to be declared and initialized *before* -// the Extended Asm block but *after* normal local variables +// 4. Furthermore, GCC Extended Asm does not support explicit register constraints +// (like `out("eax")`) directly, offering so-called "local register variables" +// as a workaround. These variables need to be declared and initialized *before* +// the Extended Asm block but *after* normal local variables // (see comment in `codegen_inline_asm` for explanation). // -// With that in mind, let's see how we translate Rust syntax to GCC +// With that in mind, let's see how we translate Rust syntax to GCC // (from now on, `CC` stands for "constraint code"): // // * `out(reg_class) var` -> translated to output operand: `"=CC"(var)` @@ -52,18 +52,17 @@ use crate::type_of::LayoutGccExt; // // * `out("explicit register") _` -> not translated to any operands, register is simply added to clobbers list // -// * `inout(reg_class) in_var => out_var` -> translated to two operands: +// * `inout(reg_class) in_var => out_var` -> translated to two operands: // output: `"=CC"(in_var)` -// input: `"num"(out_var)` where num is the GCC index +// input: `"num"(out_var)` where num is the GCC index // of the corresponding output operand // -// * `inout(reg_class) in_var => _` -> same as `inout(reg_class) in_var => tmp`, +// * `inout(reg_class) in_var => _` -> same as `inout(reg_class) in_var => tmp`, // where "tmp" is a temporary unused variable // -// * `out/in/inout("explicit register") var` -> translated to one or two operands as described above -// with `"r"(var)` constraint, +// * `out/in/inout("explicit register") var` -> translated to one or two operands as described above +// with `"r"(var)` constraint, // and one register variable assigned to the desired register. -// const ATT_SYNTAX_INS: &str = ".att_syntax noprefix\n\t"; const INTEL_SYNTAX_INS: &str = "\n\t.intel_syntax noprefix"; @@ -124,7 +123,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { let att_dialect = is_x86 && options.contains(InlineAsmOptions::ATT_SYNTAX); let intel_dialect = is_x86 && !options.contains(InlineAsmOptions::ATT_SYNTAX); - // GCC index of an output operand equals its position in the array + // GCC index of an output operand equals its position in the array let mut outputs = vec![]; // GCC index of an input operand equals its position in the array @@ -138,9 +137,9 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { let mut constants_len = 0; // There are rules we must adhere to if we want GCC to do the right thing: - // + // // * Every local variable that the asm block uses as an output must be declared *before* - // the asm block. + // the asm block. // * There must be no instructions whatsoever between the register variables and the asm. // // Therefore, the backend must generate the instructions strictly in this order: @@ -152,7 +151,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { // We also must make sure that no input operands are emitted before output operands. // // This is why we work in passes, first emitting local vars, then local register vars. - // Also, we don't emit any asm operands immediately; we save them to + // Also, we don't emit any asm operands immediately; we save them to // the one of the buffers to be emitted later. // 1. Normal variables (and saving operands to buffers). @@ -165,7 +164,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { (Constraint(constraint), Some(place)) => (constraint, place.layout.gcc_type(self.cx, false)), // When `reg` is a class and not an explicit register but the out place is not specified, // we need to create an unused output variable to assign the output to. This var - // needs to be of a type that's "compatible" with the register class, but specific type + // needs to be of a type that's "compatible" with the register class, but specific type // doesn't matter. (Constraint(constraint), None) => (constraint, dummy_output_type(self.cx, reg.reg_class())), (Register(_), Some(_)) => { @@ -193,7 +192,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { let tmp_var = self.current_func().new_local(None, ty, "output_register"); outputs.push(AsmOutOperand { - constraint, + constraint, rust_idx, late, readwrite: false, @@ -204,12 +203,12 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { InlineAsmOperandRef::In { reg, value } => { if let ConstraintOrRegister::Constraint(constraint) = reg_to_gcc(reg) { - inputs.push(AsmInOperand { - constraint: Cow::Borrowed(constraint), - rust_idx, + inputs.push(AsmInOperand { + constraint: Cow::Borrowed(constraint), + rust_idx, val: value.immediate() }); - } + } else { // left for the next pass continue @@ -219,7 +218,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { InlineAsmOperandRef::InOut { reg, late, in_value, out_place } => { let constraint = if let ConstraintOrRegister::Constraint(constraint) = reg_to_gcc(reg) { constraint - } + } else { // left for the next pass continue @@ -228,22 +227,22 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { // Rustc frontend guarantees that input and output types are "compatible", // so we can just use input var's type for the output variable. // - // This decision is also backed by the fact that LLVM needs in and out - // values to be of *exactly the same type*, not just "compatible". + // This decision is also backed by the fact that LLVM needs in and out + // values to be of *exactly the same type*, not just "compatible". // I'm not sure if GCC is so picky too, but better safe than sorry. let ty = in_value.layout.gcc_type(self.cx, false); let tmp_var = self.current_func().new_local(None, ty, "output_register"); // If the out_place is None (i.e `inout(reg) _` syntax was used), we translate - // it to one "readwrite (+) output variable", otherwise we translate it to two + // it to one "readwrite (+) output variable", otherwise we translate it to two // "out and tied in" vars as described above. let readwrite = out_place.is_none(); outputs.push(AsmOutOperand { - constraint, + constraint, rust_idx, late, readwrite, - tmp_var, + tmp_var, out_place, }); @@ -252,8 +251,8 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { let constraint = Cow::Owned(out_gcc_idx.to_string()); inputs.push(AsmInOperand { - constraint, - rust_idx, + constraint, + rust_idx, val: in_value.immediate() }); } @@ -280,7 +279,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { if let ConstraintOrRegister::Register(reg_name) = reg_to_gcc(reg) { let out_place = if let Some(place) = place { place - } + } else { // processed in the previous pass continue @@ -291,7 +290,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { tmp_var.set_register_name(reg_name); outputs.push(AsmOutOperand { - constraint: "r".into(), + constraint: "r".into(), rust_idx, late, readwrite: false, @@ -311,9 +310,9 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { reg_var.set_register_name(reg_name); self.llbb().add_assignment(None, reg_var, value.immediate()); - inputs.push(AsmInOperand { - constraint: "r".into(), - rust_idx, + inputs.push(AsmInOperand { + constraint: "r".into(), + rust_idx, val: reg_var.to_rvalue() }); } @@ -324,31 +323,23 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { // `inout("explicit register") in_var => out_var` InlineAsmOperandRef::InOut { reg, late, in_value, out_place } => { if let ConstraintOrRegister::Register(reg_name) = reg_to_gcc(reg) { - let out_place = if let Some(place) = out_place { - place - } - else { - // processed in the previous pass - continue - }; - // See explanation in the first pass. let ty = in_value.layout.gcc_type(self.cx, false); let tmp_var = self.current_func().new_local(None, ty, "output_register"); tmp_var.set_register_name(reg_name); outputs.push(AsmOutOperand { - constraint: "r".into(), + constraint: "r".into(), rust_idx, late, readwrite: false, tmp_var, - out_place: Some(out_place) + out_place, }); let constraint = Cow::Owned((outputs.len() - 1).to_string()); - inputs.push(AsmInOperand { - constraint, + inputs.push(AsmInOperand { + constraint, rust_idx, val: in_value.immediate() }); @@ -357,8 +348,8 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { // processed in the previous pass } - InlineAsmOperandRef::Const { .. } - | InlineAsmOperandRef::SymFn { .. } + InlineAsmOperandRef::Const { .. } + | InlineAsmOperandRef::SymFn { .. } | InlineAsmOperandRef::SymStatic { .. } => { // processed in the previous pass } @@ -453,7 +444,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { if !intel_dialect { template_str.push_str(INTEL_SYNTAX_INS); } - + // 4. Generate Extended Asm block let block = self.llbb(); @@ -472,7 +463,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { } if !options.contains(InlineAsmOptions::PRESERVES_FLAGS) { - // TODO(@Commeownist): I'm not 100% sure this one clobber is sufficient + // TODO(@Commeownist): I'm not 100% sure this one clobber is sufficient // on all architectures. For instance, what about FP stack? extended_asm.add_clobber("cc"); } @@ -491,10 +482,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { self.call(self.type_void(), builtin_unreachable, &[], None); } - // Write results to outputs. + // Write results to outputs. // // We need to do this because: - // 1. Turning `PlaceRef` into `RValue` is error-prone and has nasty edge cases + // 1. Turning `PlaceRef` into `RValue` is error-prone and has nasty edge cases // (especially with current `rustc_backend_ssa` API). // 2. Not every output operand has an `out_place`, and it's required by `add_output_operand`. // @@ -502,7 +493,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> { // generates `out_place = tmp_var;` assignments if out_place exists. for op in &outputs { if let Some(place) = op.out_place { - OperandValue::Immediate(op.tmp_var.to_rvalue()).store(self, place); + OperandValue::Immediate(op.tmp_var.to_rvalue()).store(self, place); } } diff --git a/tests/run/asm.rs b/tests/run/asm.rs index 9c0055b0b6b..254d946e527 100644 --- a/tests/run/asm.rs +++ b/tests/run/asm.rs @@ -17,6 +17,16 @@ extern "C" { fn add_asm(a: i64, b: i64) -> i64; } +pub unsafe fn mem_cpy(dst: *mut u8, src: *const u8, len: usize) { + asm!( + "rep movsb", + inout("rdi") dst => _, + inout("rsi") src => _, + inout("rcx") len => _, + options(preserves_flags, nostack) + ); +} + fn main() { unsafe { asm!("nop"); @@ -62,11 +72,11 @@ fn main() { } assert_eq!(x, 43); - // check inout(reg_class) x + // check inout(reg_class) x let mut x: u64 = 42; unsafe { asm!("add {0}, {0}", - inout(reg) x + inout(reg) x ); } assert_eq!(x, 84); @@ -75,7 +85,7 @@ fn main() { let mut x: u64 = 42; unsafe { asm!("add r11, r11", - inout("r11") x + inout("r11") x ); } assert_eq!(x, 84); @@ -98,12 +108,12 @@ fn main() { assert_eq!(res, 7); assert_eq!(rem, 2); - // check const + // check const let mut x: u64 = 42; unsafe { asm!("add {}, {}", inout(reg) x, - const 1 + const 1 ); } assert_eq!(x, 43); @@ -150,4 +160,11 @@ fn main() { assert_eq!(x, 42); assert_eq!(unsafe { add_asm(40, 2) }, 42); + + let array1 = [1u8, 2, 3]; + let mut array2 = [0u8, 0, 0]; + unsafe { + mem_cpy(array2.as_mut_ptr(), array1.as_ptr(), 3); + } + assert_eq!(array1, array2); } |