Merge pull request #630 from folkertdev/x86-register-classes

support `reg_byte` registers

2 files changed, 136 insertions, 101 deletions

diff --git a/src/asm.rs b/src/asm.rs
index 9f4b84d22c0..dbdf37ee6c9 100644
--- a/src/asm.rs
+++ b/src/asm.rs
@@ -611,114 +611,127 @@ fn estimate_template_length(
 }
 
 /// Converts a register class to a GCC constraint code.
-fn reg_to_gcc(reg: InlineAsmRegOrRegClass) -> ConstraintOrRegister {
-    let constraint = match reg {
-        // For vector registers LLVM wants the register name to match the type size.
+fn reg_to_gcc(reg_or_reg_class: InlineAsmRegOrRegClass) -> ConstraintOrRegister {
+    match reg_or_reg_class {
         InlineAsmRegOrRegClass::Reg(reg) => {
-            match reg {
-                InlineAsmReg::X86(_) => {
-                    // TODO(antoyo): add support for vector register.
-                    //
-                    // // For explicit registers, we have to create a register variable: https://stackoverflow.com/a/31774784/389119
-                    return ConstraintOrRegister::Register(match reg.name() {
-                        // Some of registers' names does not map 1-1 from rust to gcc
-                        "st(0)" => "st",
+            ConstraintOrRegister::Register(explicit_reg_to_gcc(reg))
+        }
+        InlineAsmRegOrRegClass::RegClass(reg_class) => {
+            ConstraintOrRegister::Constraint(reg_class_to_gcc(reg_class))
+        }
+    }
+}
 
-                        name => name,
-                    });
+fn explicit_reg_to_gcc(reg: InlineAsmReg) -> &'static str {
+    // For explicit registers, we have to create a register variable: https://stackoverflow.com/a/31774784/389119
+    match reg {
+        InlineAsmReg::X86(reg) => {
+            // TODO(antoyo): add support for vector register.
+            match reg.reg_class() {
+                X86InlineAsmRegClass::reg_byte => {
+                    // GCC does not support the `b` suffix, so we just strip it
+                    // see https://github.com/rust-lang/rustc_codegen_gcc/issues/485
+                    reg.name().trim_end_matches('b')
                 }
+                _ => match reg.name() {
+                    // Some of registers' names does not map 1-1 from rust to gcc
+                    "st(0)" => "st",
 
-                _ => unimplemented!(),
+                    name => name,
+                },
             }
         }
-        // They can be retrieved from https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html
-        InlineAsmRegOrRegClass::RegClass(reg) => match reg {
-            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::sreg)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg_low16)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg_low8)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::sreg_low16)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg_low8)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg_low4)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg)
-            | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg) => "t",
-            InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_upper) => "d",
-            InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_pair) => "r",
-            InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_iw) => "w",
-            InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_ptr) => "e",
-            InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::wreg) => "w",
-            InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::preg) => {
-                unreachable!("clobber-only")
-            }
-            InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::freg) => "f",
-            InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg_addr) => "a",
-            InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg_data) => "d",
-            InlineAsmRegClass::CSKY(CSKYInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::CSKY(CSKYInlineAsmRegClass::freg) => "f",
-            InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg) => "d", // more specific than "r"
-            InlineAsmRegClass::Mips(MipsInlineAsmRegClass::freg) => "f",
-            InlineAsmRegClass::Msp430(Msp430InlineAsmRegClass::reg) => "r",
-            // https://github.com/gcc-mirror/gcc/blob/master/gcc/config/nvptx/nvptx.md -> look for
-            // "define_constraint".
-            InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg16) => "h",
-            InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg32) => "r",
-            InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg64) => "l",
-
-            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg_nonzero) => "b",
-            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => "f",
-            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::vreg) => "v",
-            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::cr)
-            | InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::xer) => {
-                unreachable!("clobber-only")
-            }
-            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::kreg0
-                | X86InlineAsmRegClass::x87_reg
-                | X86InlineAsmRegClass::mmx_reg
-                | X86InlineAsmRegClass::tmm_reg,
-            ) => unreachable!("clobber-only"),
-            InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
-                bug!("GCC backend does not support SPIR-V")
-            }
-            InlineAsmRegClass::Wasm(WasmInlineAsmRegClass::local) => "r",
-            InlineAsmRegClass::S390x(S390xInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::S390x(S390xInlineAsmRegClass::reg_addr) => "a",
-            InlineAsmRegClass::S390x(S390xInlineAsmRegClass::freg) => "f",
-            InlineAsmRegClass::S390x(S390xInlineAsmRegClass::vreg) => "v",
-            InlineAsmRegClass::S390x(S390xInlineAsmRegClass::areg) => {
-                unreachable!("clobber-only")
-            }
-            InlineAsmRegClass::Sparc(SparcInlineAsmRegClass::reg) => "r",
-            InlineAsmRegClass::Sparc(SparcInlineAsmRegClass::yreg) => unreachable!("clobber-only"),
-            InlineAsmRegClass::Err => unreachable!(),
-        },
-    };
 
-    ConstraintOrRegister::Constraint(constraint)
+        _ => unimplemented!(),
+    }
+}
+
+/// They can be retrieved from https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html
+fn reg_class_to_gcc(reg_class: InlineAsmRegClass) -> &'static str {
+    match reg_class {
+        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::sreg)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg_low16)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg_low8)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::sreg_low16)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg_low8)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg_low4)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::dreg)
+        | InlineAsmRegClass::Arm(ArmInlineAsmRegClass::qreg) => "t",
+        InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_upper) => "d",
+        InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_pair) => "r",
+        InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_iw) => "w",
+        InlineAsmRegClass::Avr(AvrInlineAsmRegClass::reg_ptr) => "e",
+        InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::Bpf(BpfInlineAsmRegClass::wreg) => "w",
+        InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::Hexagon(HexagonInlineAsmRegClass::preg) => {
+            unreachable!("clobber-only")
+        }
+        InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::LoongArch(LoongArchInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg_addr) => "a",
+        InlineAsmRegClass::M68k(M68kInlineAsmRegClass::reg_data) => "d",
+        InlineAsmRegClass::CSKY(CSKYInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::CSKY(CSKYInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::Mips(MipsInlineAsmRegClass::reg) => "d", // more specific than "r"
+        InlineAsmRegClass::Mips(MipsInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::Msp430(Msp430InlineAsmRegClass::reg) => "r",
+        // https://github.com/gcc-mirror/gcc/blob/master/gcc/config/nvptx/nvptx.md -> look for
+        // "define_constraint".
+        InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg16) => "h",
+        InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg32) => "r",
+        InlineAsmRegClass::Nvptx(NvptxInlineAsmRegClass::reg64) => "l",
+
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg_nonzero) => "b",
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::vreg) => "v",
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::cr)
+        | InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::xer) => {
+            unreachable!("clobber-only")
+        }
+        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::kreg0
+            | X86InlineAsmRegClass::x87_reg
+            | X86InlineAsmRegClass::mmx_reg
+            | X86InlineAsmRegClass::tmm_reg,
+        ) => unreachable!("clobber-only"),
+        InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
+            bug!("GCC backend does not support SPIR-V")
+        }
+        InlineAsmRegClass::Wasm(WasmInlineAsmRegClass::local) => "r",
+        InlineAsmRegClass::S390x(S390xInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::S390x(S390xInlineAsmRegClass::reg_addr) => "a",
+        InlineAsmRegClass::S390x(S390xInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::S390x(S390xInlineAsmRegClass::vreg) => "v",
+        InlineAsmRegClass::S390x(S390xInlineAsmRegClass::areg) => {
+            unreachable!("clobber-only")
+        }
+        InlineAsmRegClass::Sparc(SparcInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::Sparc(SparcInlineAsmRegClass::yreg) => unreachable!("clobber-only"),
+        InlineAsmRegClass::Err => unreachable!(),
+    }
 }
 
 /// Type to use for outputs that are discarded. It doesn't really matter what
diff --git a/tests/run/asm.rs b/tests/run/asm.rs
index 9ede19a061f..2dbf43be664 100644
--- a/tests/run/asm.rs
+++ b/tests/run/asm.rs
@@ -205,6 +205,28 @@ fn asm() {
         }
         assert_eq!((x, y), (16, 16));
     }
+
+    // the `b` suffix for registers in the `reg_byte` register class is not supported in GCC
+    // and needs to be stripped in order to use these registers.
+    unsafe {
+        core::arch::asm!(
+            "",
+            out("al") _,
+            out("bl") _,
+            out("cl") _,
+            out("dl") _,
+            out("sil") _,
+            out("dil") _,
+            out("r8b") _,
+            out("r9b") _,
+            out("r10b") _,
+            out("r11b") _,
+            out("r12b") _,
+            out("r13b") _,
+            out("r14b") _,
+            out("r15b") _,
+        );
+    }
 }
 
 #[cfg(not(target_arch = "x86_64"))]