Auto merge of #1048 - Aaron1011:panic-rustup, r=RalfJung

Rustup for panic changes

This gets Miri working again, but doesn't actually implement unwinding

Author: bors

README.md

@@ -172,6 +172,11 @@ Several `-Z` flags are relevant for Miri:
   sets this flag per default.
 * `-Zmir-emit-retag` controls whether `Retag` statements are emitted. Miri
   enables this per default because it is needed for validation.
+* `-Zno-codegen` makes rustc skip generating LLVM IR for MIR (though it still
+  writes out empty object files). This is needed to prevent rustc from trying
+  to codegen certain panic-related intrinsics, which will not work with a
+  `libpanic_unwind` compiled in `cfg(miri)` mode. It also speeds up
+  building our custom libstd.
 
 Moreover, Miri recognizes some environment variables:
 

rust-version

@@ -1 +1 @@
-56237d75b4271a8a2e0f47d86ea76ebf6d966152
+a333eed7fc0c903df9d6befcfb40af02148bf255

src/eval.rs

@@ -213,7 +213,7 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) {
             };
             e.print_backtrace();
             if let Some(frame) = ecx.stack().last() {
-                let block = &frame.body.basic_blocks()[frame.block];
+                let block = &frame.body.basic_blocks()[frame.block.unwrap()];
                 let span = if frame.stmt < block.statements.len() {
                     block.statements[frame.stmt].source_info.span
                 } else {

src/lib.rs

@@ -51,5 +51,5 @@ pub use crate::eval::{eval_main, create_ecx, MiriConfig};
 /// Insert rustc arguments at the beginning of the argument list that Miri wants to be
 /// set per default, for maximal validation power.
 pub fn miri_default_args() -> &'static [&'static str] {
-    &["-Zalways-encode-mir", "-Zmir-emit-retag", "-Zmir-opt-level=0", "--cfg=miri"]
+    &["-Zalways-encode-mir", "-Zmir-emit-retag", "-Zmir-opt-level=0", "-Zno-codegen", "--cfg=miri"]
 }

src/machine.rs

@@ -173,6 +173,7 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         args: &[OpTy<'tcx, Tag>],
         dest: Option<PlaceTy<'tcx, Tag>>,
         ret: Option<mir::BasicBlock>,
+        _unwind: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
         ecx.find_fn(instance, args, dest, ret)
     }
@@ -194,8 +195,14 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         span: Span,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx, Tag>],
-        dest: PlaceTy<'tcx, Tag>,
+        dest: Option<PlaceTy<'tcx, Tag>>,
+        _ret: Option<mir::BasicBlock>,
+        _unwind: Option<mir::BasicBlock>
     ) -> InterpResult<'tcx> {
+        let dest = match dest {
+            Some(dest) => dest,
+            None => throw_ub!(Unreachable)
+        };
         ecx.call_intrinsic(span, instance, args, dest)
     }
 
@@ -353,13 +360,15 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     fn stack_pop(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
         extra: stacked_borrows::CallId,
-    ) -> InterpResult<'tcx> {
-        Ok(ecx
+        _unwinding: bool
+    ) -> InterpResult<'tcx, StackPopInfo> {
+        ecx
             .memory
             .extra
             .stacked_borrows
             .borrow_mut()
-            .end_call(extra))
+            .end_call(extra);
+        Ok(StackPopInfo::Normal)
     }
 
     #[inline(always)]

src/shims/foreign_items.rs

@@ -335,7 +335,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                     mir,
                     Some(ret_place),
                     // Directly return to caller.
-                    StackPopCleanup::Goto(Some(ret)),
+                    StackPopCleanup::Goto { ret: Some(ret), unwind: None },
                 )?;
                 let mut args = this.frame().body.args_iter();
 

src/shims/intrinsics.rs

@@ -22,7 +22,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         dest: PlaceTy<'tcx, Tag>,
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
-        if this.emulate_intrinsic(span, instance, args, dest)? {
+        if this.emulate_intrinsic(span, instance, args, Some(dest))? {
             return Ok(());
         }
         let tcx = &{this.tcx.tcx};

src/shims/mod.rs

@@ -27,7 +27,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         );
 
         // First, run the common hooks also supported by CTFE.
-        if this.hook_fn(instance, args, dest)? {
+        if this.hook_panic_fn(instance, args, dest)? {
             this.goto_block(ret)?;
             return Ok(None);
         }