Support AVRTiny devices AVR inline assembly

taiki-e · taiki-e · commit 2a9be6446bb8 · 2025-09-23T02:49:34.000+09:00
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -2198,6 +2198,7 @@ symbols! {
         three_way_compare,
         thumb2,
         thumb_mode: "thumb-mode",
+        tinyencoding,
         tmm_reg,
         to_owned_method,
         to_string,
diff --git a/compiler/rustc_target/src/asm/avr.rs b/compiler/rustc_target/src/asm/avr.rs
@@ -1,8 +1,10 @@
 use std::fmt;
 
-use rustc_span::Symbol;
+use rustc_data_structures::fx::FxIndexSet;
+use rustc_span::{Symbol, sym};
 
 use super::{InlineAsmArch, InlineAsmType, ModifierInfo};
+use crate::spec::{RelocModel, Target};
 
 def_reg_class! {
     Avr AvrInlineAsmRegClass {
@@ -52,24 +54,44 @@ impl AvrInlineAsmRegClass {
     }
 }
 
+pub(crate) fn is_tiny(target_features: &FxIndexSet<Symbol>) -> bool {
+    target_features.contains(&sym::tinyencoding)
+}
+
+fn not_tiny(
+    _arch: InlineAsmArch,
+    _reloc_model: RelocModel,
+    target_features: &FxIndexSet<Symbol>,
+    _target: &Target,
+    _is_clobber: bool,
+) -> Result<(), &'static str> {
+    if is_tiny(target_features) {
+        Err(
+            "on AVRTiny, r[2-15] are unavailable, r16 (scratch register) and r17 (zero register) are reserved by LLVM",
+        )
+    } else {
+        Ok(())
+    }
+}
+
 def_regs! {
     Avr AvrInlineAsmReg AvrInlineAsmRegClass {
-        r2: reg = ["r2"],
-        r3: reg = ["r3"],
-        r4: reg = ["r4"],
-        r5: reg = ["r5"],
-        r6: reg = ["r6"],
-        r7: reg = ["r7"],
-        r8: reg = ["r8"],
-        r9: reg = ["r9"],
-        r10: reg = ["r10"],
-        r11: reg = ["r11"],
-        r12: reg = ["r12"],
-        r13: reg = ["r13"],
-        r14: reg = ["r14"],
-        r15: reg = ["r15"],
-        r16: reg, reg_upper = ["r16"],
-        r17: reg, reg_upper = ["r17"],
+        r2: reg = ["r2"] % not_tiny,
+        r3: reg = ["r3"] % not_tiny,
+        r4: reg = ["r4"] % not_tiny,
+        r5: reg = ["r5"] % not_tiny,
+        r6: reg = ["r6"] % not_tiny,
+        r7: reg = ["r7"] % not_tiny,
+        r8: reg = ["r8"] % not_tiny,
+        r9: reg = ["r9"] % not_tiny,
+        r10: reg = ["r10"] % not_tiny,
+        r11: reg = ["r11"] % not_tiny,
+        r12: reg = ["r12"] % not_tiny,
+        r13: reg = ["r13"] % not_tiny,
+        r14: reg = ["r14"] % not_tiny,
+        r15: reg = ["r15"] % not_tiny,
+        r16: reg, reg_upper = ["r16"] % not_tiny,
+        r17: reg, reg_upper = ["r17"] % not_tiny,
         r18: reg, reg_upper = ["r18"],
         r19: reg, reg_upper = ["r19"],
         r20: reg, reg_upper = ["r20"],
@@ -83,14 +105,14 @@ def_regs! {
         r30: reg, reg_upper = ["r30", "ZL"],
         r31: reg, reg_upper = ["r31", "ZH"],
 
-        r3r2: reg_pair = ["r3r2"],
-        r5r4: reg_pair = ["r5r4"],
-        r7r6: reg_pair = ["r7r6"],
-        r9r8: reg_pair = ["r9r8"],
-        r11r10: reg_pair = ["r11r10"],
-        r13r12: reg_pair = ["r13r12"],
-        r15r14: reg_pair = ["r15r14"],
-        r17r16: reg_pair = ["r17r16"],
+        r3r2: reg_pair = ["r3r2"] % not_tiny,
+        r5r4: reg_pair = ["r5r4"] % not_tiny,
+        r7r6: reg_pair = ["r7r6"] % not_tiny,
+        r9r8: reg_pair = ["r9r8"] % not_tiny,
+        r11r10: reg_pair = ["r11r10"] % not_tiny,
+        r13r12: reg_pair = ["r13r12"] % not_tiny,
+        r15r14: reg_pair = ["r15r14"] % not_tiny,
+        r17r16: reg_pair = ["r17r16"] % not_tiny,
         r19r18: reg_pair = ["r19r18"],
         r21r20: reg_pair = ["r21r20"],
         r23r22: reg_pair = ["r23r22"],
diff --git a/compiler/rustc_target/src/asm/mod.rs b/compiler/rustc_target/src/asm/mod.rs
@@ -935,6 +935,7 @@ pub enum InlineAsmClobberAbi {
     AArch64NoX18,
     Arm64EC,
     Avr,
+    AvrTiny,
     RiscV,
     RiscVE,
     LoongArch,
@@ -995,7 +996,11 @@ impl InlineAsmClobberAbi {
                 _ => Err(&["C", "system", "efiapi"]),
             },
             InlineAsmArch::Avr => match name {
-                "C" | "system" => Ok(InlineAsmClobberAbi::Avr),
+                "C" | "system" => Ok(if avr::is_tiny(target_features) {
+                    InlineAsmClobberAbi::AvrTiny
+                } else {
+                    InlineAsmClobberAbi::Avr
+                }),
                 _ => Err(&["C", "system"]),
             },
             InlineAsmArch::LoongArch32 | InlineAsmArch::LoongArch64 => match name {
@@ -1166,6 +1171,13 @@ impl InlineAsmClobberAbi {
                     // is used.
                 }
             },
+            InlineAsmClobberAbi::AvrTiny => clobbered_regs! {
+                Avr AvrInlineAsmReg {
+                    // Refs: https://gcc.gnu.org/wiki/avr-gcc#Reduced_Tiny
+
+                    r20, r21, r22, r23, r24, r25, r26, r27, r30, r31,
+                }
+            },
             InlineAsmClobberAbi::RiscV => clobbered_regs! {
                 RiscV RiscVInlineAsmReg {
                     // ra
diff --git a/tests/codegen-llvm/asm/avr-clobbers.rs b/tests/codegen-llvm/asm/avr-clobbers.rs
@@ -1,7 +1,10 @@
 //@ add-core-stubs
 //@ assembly-output: emit-asm
-//@ compile-flags: --target avr-none -C target-cpu=atmega328p
-//@ needs-llvm-components: avr
+//@ revisions: avr avrtiny
+//@[avr] compile-flags: --target avr-none -C target-cpu=atmega328p
+//@[avr] needs-llvm-components: avr
+//@[avrtiny] compile-flags: --target avr-none -C target-cpu=attiny104
+//@[avrtiny] needs-llvm-components: avr
 
 #![crate_type = "rlib"]
 #![feature(no_core, asm_experimental_arch)]
@@ -25,14 +28,16 @@ pub unsafe fn sreg_is_not_clobbered_if_preserve_flags_is_used() {
 }
 
 // CHECK-LABEL: @clobber_abi
-// CHECK: asm sideeffect "", "={r18},={r19},={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31},~{sreg}"()
+// avr: asm sideeffect "", "={r18},={r19},={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31},~{sreg}"()
+// avrtiny: asm sideeffect "", "={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31},~{sreg}"()
 #[no_mangle]
 pub unsafe fn clobber_abi() {
     asm!("", clobber_abi("C"), options(nostack, nomem));
 }
 
 // CHECK-LABEL: @clobber_abi_with_preserved_flags
-// CHECK: asm sideeffect "", "={r18},={r19},={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31}"()
+// avr: asm sideeffect "", "={r18},={r19},={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31}"()
+// avrtiny: asm sideeffect "", "={r20},={r21},={r22},={r23},={r24},={r25},={r26},={r27},={r30},={r31}"()
 #[no_mangle]
 pub unsafe fn clobber_abi_with_preserved_flags() {
     asm!("", clobber_abi("C"), options(nostack, nomem, preserves_flags));
