Add Xtensa targets for the ESP-IDF framework

Author: imarkov

compiler/rustc_target/src/spec/mod.rs

@@ -886,7 +886,9 @@ supported_targets! {
     ("nvptx64-nvidia-cuda", nvptx64_nvidia_cuda),
 
     ("xtensa-esp32-none-elf", xtensa_esp32_none_elf),
+    ("xtensa-esp32-espidf", xtensa_esp32_espidf),
     ("xtensa-esp32s2-none-elf", xtensa_esp32s2_none_elf),
+    ("xtensa-esp32s2-espidf", xtensa_esp32s2_espidf),
     ("xtensa-esp8266-none-elf", xtensa_esp8266_none_elf),
     ("xtensa-none-elf", xtensa_none_elf),
 

compiler/rustc_target/src/spec/xtensa_esp32_espidf.rs

@@ -0,0 +1,51 @@
+use crate::spec::{abi::Abi, LinkerFlavor, PanicStrategy, Target, TargetOptions, RelocModel};
+use crate::abi::Endian;
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "xtensa-none-elf".to_string(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-i8:8:32-i16:16:32-i64:64-n32".to_string(),
+        arch: "xtensa".to_string(),
+
+        options: TargetOptions {
+            endian: Endian::Little,
+            c_int_width: "32".to_string(),
+            families: vec!["unix".to_string()],
+            os: "espidf".to_string(),
+            env: "newlib".to_string(),
+            vendor: "espressif".to_string(),
+            linker_flavor: LinkerFlavor::Gcc,
+
+            executables: true,
+            cpu: "esp32".to_string(),
+            linker: Some("xtensa-esp32-elf-gcc".to_string()),
+
+            max_atomic_width: Some(32),
+
+            // Because these devices have very little resources having an
+            // unwinder is too onerous so we default to "abort" because the
+            // "unwind" strategy is very rare.
+            panic_strategy: PanicStrategy::Abort,
+
+            // Similarly, one almost always never wants to use relocatable
+            // code because of the extra costs it involves.
+            relocation_model: RelocModel::Static,
+
+            emit_debug_gdb_scripts: false,
+
+            unsupported_abis: vec![
+                Abi::Stdcall { unwind: false },
+                Abi::Stdcall { unwind: true },
+                Abi::Fastcall,
+                Abi::Vectorcall,
+                Abi::Thiscall { unwind: false },
+                Abi::Thiscall { unwind: true },
+                Abi::Win64,
+                Abi::SysV64,
+            ],
+
+            ..Default::default()
+        },
+    }
+}

compiler/rustc_target/src/spec/xtensa_esp32s2_espidf.rs

@@ -0,0 +1,62 @@
+use crate::spec::{abi::Abi, LinkerFlavor, PanicStrategy, Target, TargetOptions, RelocModel};
+use crate::abi::Endian;
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "xtensa-none-elf".to_string(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-i8:8:32-i16:16:32-i64:64-n32".to_string(),
+        arch: "xtensa".to_string(),
+
+        options: TargetOptions {
+            endian: Endian::Little,
+            c_int_width: "32".to_string(),
+            families: vec!["unix".to_string()],
+            os: "espidf".to_string(),
+            env: "newlib".to_string(),
+            vendor: "espressif".to_string(),
+            linker_flavor: LinkerFlavor::Gcc,
+
+            executables: true,
+            cpu: "esp32-s2".to_string(),
+            linker: Some("xtensa-esp32s2-elf-gcc".to_string()),
+
+            // See https://github.com/espressif/rust-esp32-example/issues/3#issuecomment-861054477
+            //
+            // Unlike the original ESP32 chip, ESP32-S2 does not really support atomics.
+            // If the missing hardware instruction ends up being emulated in ESP-IDF, we might want to revert
+            // this change and claim that atomics are supported "in hardware" (even though they would be emulated
+            // by actually trapping the illegal instruction exception handler and calling into an ESP-IDF C emulation code).
+            //
+            // However, for now we simultaneously claim "max_atomic_width: Some(32)" **and** atomic_cas: true,
+            // which should force the compiler to generate libcalls to functions that emulate atomics
+            // and which are already implemented in the ESP-IDF main branch anyway.
+            max_atomic_width: Some(32),
+            atomic_cas: true,
+
+            // Because these devices have very little resources having an
+            // unwinder is too onerous so we default to "abort" because the
+            // "unwind" strategy is very rare.
+            panic_strategy: PanicStrategy::Abort,
+
+            // Similarly, one almost always never wants to use relocatable
+            // code because of the extra costs it involves.
+            relocation_model: RelocModel::Static,
+
+            emit_debug_gdb_scripts: false,
+
+            unsupported_abis: vec![
+                Abi::Stdcall { unwind: false },
+                Abi::Stdcall { unwind: true },
+                Abi::Fastcall,
+                Abi::Vectorcall,
+                Abi::Thiscall { unwind: false },
+                Abi::Thiscall { unwind: true },
+                Abi::Win64,
+                Abi::SysV64,
+            ],
+
+            ..Default::default()
+        },
+    }
+}