Make coverage counter IDs count up from 0, not 1

Operand types are now tracked explicitly, so there is no need to reserve ID 0
for the special always-zero counter.

As part of the renumbering, this change fixes an off-by-one error in the way
counters were counted by the `coverageinfo` query. As a result, functions
should now have exactly the number of counters they actually need, instead of
always having an extra counter that is never used.

1 files changed, 4 insertions, 6 deletions

diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index 5e0c5df2bcb..c1017ab8d7c 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -16,9 +16,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_llvm::RustString;
 use rustc_middle::bug;
-use rustc_middle::mir::coverage::{
-    CodeRegion, CounterValueReference, CoverageKind, ExpressionId, Op, Operand,
-};
+use rustc_middle::mir::coverage::{CodeRegion, CounterId, CoverageKind, ExpressionId, Op, Operand};
 use rustc_middle::mir::Coverage;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
@@ -33,7 +31,7 @@ mod ffi;
 pub(crate) mod map_data;
 pub mod mapgen;
 
-const UNUSED_FUNCTION_COUNTER_ID: CounterValueReference = CounterValueReference::START;
+const UNUSED_FUNCTION_COUNTER_ID: CounterId = CounterId::START;
 
 const VAR_ALIGN_BYTES: usize = 8;
 
@@ -125,7 +123,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
                     let fn_name = bx.get_pgo_func_name_var(instance);
                     let hash = bx.const_u64(function_source_hash);
                     let num_counters = bx.const_u32(coverageinfo.num_counters);
-                    let index = bx.const_u32(id.zero_based_index());
+                    let index = bx.const_u32(id.as_u32());
                     debug!(
                         "codegen intrinsic instrprof.increment(fn_name={:?}, hash={:?}, num_counters={:?}, index={:?})",
                         fn_name, hash, num_counters, index,
@@ -178,7 +176,7 @@ impl<'tcx> Builder<'_, '_, 'tcx> {
     fn add_coverage_counter(
         &mut self,
         instance: Instance<'tcx>,
-        id: CounterValueReference,
+        id: CounterId,
         region: CodeRegion,
     ) -> bool {
         if let Some(coverage_context) = self.coverage_context() {