[RISC-V] Do not force frame pointers

src/bootstrap/compile.rs

@@ -244,6 +244,16 @@ pub fn std_cargo(builder: &Builder<'_>, target: Interned<String>, stage: u32, ca
     if stage >= 1 {
         cargo.rustflag("-Cembed-bitcode=yes");
     }
+
+    // By default, rustc does not include unwind tables unless they are required
+    // for a particular target. They are not required by RISC-V targets, but
+    // compiling the standard library with them means that users can get
+    // backtraces without having to recompile the standard library themselves.
+    //
+    // This choice was discussed in https://github.com/rust-lang/rust/pull/69890
+    if target.contains("riscv") {
+        cargo.rustflag("-Cforce-unwind-tables=yes");
+    }
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]

src/librustc_target/spec/riscv32i_unknown_none_elf.rs

@@ -25,7 +25,6 @@ pub fn target() -> TargetResult {
             relocation_model: RelocModel::Static,
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
-            eliminate_frame_pointer: false,
             ..Default::default()
         },
     })

src/librustc_target/spec/riscv32imac_unknown_none_elf.rs

@@ -25,7 +25,6 @@ pub fn target() -> TargetResult {
             relocation_model: RelocModel::Static,
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
-            eliminate_frame_pointer: false,
             ..Default::default()
         },
     })

src/librustc_target/spec/riscv32imc_unknown_none_elf.rs

@@ -25,7 +25,6 @@ pub fn target() -> TargetResult {
             relocation_model: RelocModel::Static,
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
-            eliminate_frame_pointer: false,
             ..Default::default()
         },
     })

src/librustc_target/spec/riscv64gc_unknown_none_elf.rs

@@ -26,7 +26,6 @@ pub fn target() -> TargetResult {
             code_model: Some(CodeModel::Medium),
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
-            eliminate_frame_pointer: false,
             ..Default::default()
         },
     })

src/librustc_target/spec/riscv64imac_unknown_none_elf.rs

@@ -26,7 +26,6 @@ pub fn target() -> TargetResult {
             code_model: Some(CodeModel::Medium),
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
-            eliminate_frame_pointer: false,
             ..Default::default()
         },
     })