moved to post_borrowck_cleanup & used MirPatch

Author: richkadel

src/librustc_mir/interpret/intrinsics.rs

@@ -389,6 +389,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 );
                 self.copy_op(self.operand_index(args[0], index)?, dest)?;
             }
+            sym::count_code_region => (),
             _ => return Ok(false),
         }
 

src/librustc_mir/transform/instrument_coverage.rs

@@ -1,8 +1,7 @@
 use crate::transform::{MirPass, MirSource};
-use rustc_index::vec::Idx;
+use crate::util::patch::MirPatch;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::*;
-use rustc_middle::mir::{Local, LocalDecl};
 use rustc_middle::ty;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::TyCtxt;
@@ -16,69 +15,62 @@ pub struct InstrumentCoverage;
  * the intrinsic llvm.instrprof.increment.
  */
 
-// FIXME(richkadel): As a first step, counters are only injected at the top of each function.
-// The complete solution will inject counters at each conditional code branch.
-
 impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
         if tcx.sess.opts.debugging_opts.instrument_coverage {
-            if let Some(callee_fn_def_id) = tcx.lang_items().count_code_region_fn() {
-                debug!("instrumenting {:?}", src.def_id());
-                instrument_coverage(tcx, callee_fn_def_id, body);
-            }
+            debug!("instrumenting {:?}", src.def_id());
+            instrument_coverage(tcx, body);
         }
     }
 }
 
-pub fn instrument_coverage<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    callee_fn_def_id: DefId,
-    body: &mut Body<'tcx>,
-) {
+// The first counter (start of the function) is index zero.
+const INIT_FUNCTION_COUNTER: u128 = 0;
+
+/// Injects calls to placeholder function `count_code_region()`.
+// FIXME(richkadel): As a first step, counters are only injected at the top of each function.
+// The complete solution will inject counters at each conditional code branch.
+pub fn instrument_coverage<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let span = body.span.shrink_to_lo();
 
-    let ret_ty = tcx.fn_sig(callee_fn_def_id).output();
+    let count_code_region_fn =
+        function_handle(tcx, span, tcx.lang_items().count_code_region_fn().unwrap());
+    let counter_index = const_int_operand(tcx, span, tcx.types.u32, INIT_FUNCTION_COUNTER);
+
+    let mut patch = MirPatch::new(body);
+
+    let new_block = patch.new_block(placeholder_block(SourceInfo::outermost(body.span)));
+    let next_block = START_BLOCK;
+
+    let temp = patch.new_temp(tcx.mk_unit(), body.span);
+    patch.patch_terminator(
+        new_block,
+        TerminatorKind::Call {
+            func: count_code_region_fn,
+            args: vec![counter_index],
+            // new_block will swapped with the next_block, after applying patch
+            destination: Some((Place::from(temp), new_block)),
+            cleanup: None,
+            from_hir_call: false,
+        },
+    );
+
+    patch.add_statement(new_block.start_location(), StatementKind::StorageLive(temp));
+    patch.add_statement(next_block.start_location(), StatementKind::StorageDead(temp));
+
+    patch.apply(body);
+
+    // To insert the `new_block` in front of the first block in the counted branch (for example,
+    // the START_BLOCK, at the top of the function), just swap the indexes, leaving the rest of the
+    // graph unchanged.
+    body.basic_blocks_mut().swap(next_block, new_block);
+}
+
+fn function_handle<'tcx>(tcx: TyCtxt<'tcx>, span: Span, fn_def_id: DefId) -> Operand<'tcx> {
+    let ret_ty = tcx.fn_sig(fn_def_id).output();
     let ret_ty = ret_ty.no_bound_vars().unwrap();
     let substs = tcx.mk_substs(::std::iter::once(ty::subst::GenericArg::from(ret_ty)));
-
-    let count_code_region_fn: Operand<'_> =
-        Operand::function_handle(tcx, callee_fn_def_id, substs, span);
-
-    let index = const_int_operand(tcx, span.clone(), tcx.types.u32, 0);
-
-    let args = vec![index];
-
-    let source_info = SourceInfo { span: span, scope: OUTERMOST_SOURCE_SCOPE };
-
-    let new_block = START_BLOCK + body.basic_blocks().len();
-
-    let next_local = body.local_decls.len();
-    let new_temp = Local::new(next_local);
-    let unit_temp = Place::from(new_temp);
-
-    let storage_live = Statement { source_info, kind: StatementKind::StorageLive(new_temp) };
-    let storage_dead = Statement { source_info, kind: StatementKind::StorageDead(new_temp) };
-
-    let count_code_region_call = TerminatorKind::Call {
-        func: count_code_region_fn,
-        args,
-        destination: Some((unit_temp, new_block)),
-        cleanup: None,
-        from_hir_call: false,
-    };
-
-    body.local_decls.push(LocalDecl::new(tcx.mk_unit(), body.span));
-    body.basic_blocks_mut().push(BasicBlockData {
-        statements: vec![storage_live],
-        is_cleanup: false,
-        terminator: Some(Terminator { source_info, kind: count_code_region_call }),
-    });
-
-    body.basic_blocks_mut().swap(START_BLOCK, new_block);
-    body[new_block].statements.push(storage_dead);
-
-    // FIXME(richkadel): ALSO add each computed Span for each conditional branch to the coverage map
-    // and provide that map to LLVM to encode in the final binary.
+    Operand::function_handle(tcx, fn_def_id, substs, span)
 }
 
 fn const_int_operand<'tcx>(
@@ -98,3 +90,15 @@ fn const_int_operand<'tcx>(
         literal: ty::Const::from_scalar(tcx, Scalar::from_uint(val, size), ty),
     })
 }
+
+fn placeholder_block<'tcx>(source_info: SourceInfo) -> BasicBlockData<'tcx> {
+    BasicBlockData {
+        statements: vec![],
+        terminator: Some(Terminator {
+            source_info,
+            // this gets overwritten by the counter Call
+            kind: TerminatorKind::Unreachable,
+        }),
+        is_cleanup: false,
+    }
+}

src/librustc_mir/transform/mod.rs

@@ -288,8 +288,6 @@ fn mir_validated(
         &[&[
             // What we need to run borrowck etc.
             &promote_pass,
-            // FIXME(richkadel): is this the best place for the InstrumentCoverage pass?
-            &instrument_coverage::InstrumentCoverage,
             &simplify::SimplifyCfg::new("qualify-consts"),
         ]],
     );
@@ -340,6 +338,10 @@ fn run_post_borrowck_cleanup_passes<'tcx>(
         // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
         // but before optimizations begin.
         &add_retag::AddRetag,
+        // If the `instrument-coverage` option is enabled, analyze the CFG, identify each
+        // conditional branch, construct a coverage map to be passed to LLVM, and inject counters
+        // where needed.
+        &instrument_coverage::InstrumentCoverage,
         &simplify::SimplifyCfg::new("elaborate-drops"),
     ];
 

src/librustc_session/options.rs

@@ -877,8 +877,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         (such as entering an empty infinite loop) by inserting llvm.sideeffect \
         (default: no)"),
     instrument_coverage: bool = (false, parse_bool, [TRACKED],
-        "instrument the generated code with LLVM code region counters for \
-        generating coverage reports (default: no)"),
+        "instrument the generated code with LLVM code region counters to \
+        (in the future) generate coverage reports (experimental; default: no)"),
     instrument_mcount: bool = (false, parse_bool, [TRACKED],
         "insert function instrument code for mcount-based tracing (default: no)"),
     keep_hygiene_data: bool = (false, parse_bool, [UNTRACKED],