Cover the function-definition line of device code.

src/compiler/codegen/expressions.jl

@@ -221,6 +221,30 @@ function record_coverage!(ctx::CGCtx)
     line > 0 || return nothing
     file = string(loc.file)
     isempty(file) && return nothing
+    ccall(:jl_coverage_visit_line, Cvoid, (Cstring, Csize_t, Cint),
+          file, ncodeunits(file), line)
+    ctx.recorded_coverage = true
+    return nothing
+end
+
+# The per-statement `:code_coverage_effect`s only cover body lines. Julia's codegen
+# visits the function-definition (signature) line separately at the prologue
+# (`toplineno`); mirror that here, or the signature is reported as missed while the
+# body is hit. Only for tracked kernels (body carried coverage effects), to avoid
+# reporting signatures of untracked code.
+function record_definition_coverage!(ctx::CGCtx)
+    Base.JLOptions().code_coverage == 0 && return nothing
+    ctx.recorded_coverage || return nothing
+    inst = first_located_instruction(ctx.sci, ctx.sci.entry)
+    inst === nothing && return nothing
+    stack = source_location(ctx.sci, inst)
+    isempty(stack) && return nothing
+    outer = stack[1]                       # outermost frame = the kernel itself
+    m = outer.method
+    m isa MethodInstance && (m = m.def)
+    file = string(m isa Method ? m.file : outer.file)
+    line = Int(m isa Method ? m.line : outer.line)
+    (isempty(file) || line <= 0) && return nothing
     ccall(:jl_coverage_visit_line, Cvoid, (Cstring, Csize_t, Cint),
           file, ncodeunits(file), line)
     return nothing

src/compiler/codegen/kernel.jl

@@ -188,6 +188,10 @@ function emit_kernel!(writer::BytecodeWriter, func_buf::Vector{UInt8},
     # Emit the structured IR (uses original Julia SSA indices everywhere)
     emit_block!(ctx, ctx.sci.entry)
 
+    # Cover the function-definition line (Julia's codegen does this at the
+    # prologue; the per-statement coverage effects only cover body lines).
+    record_definition_coverage!(ctx)
+
     finalize_function!(func_buf, cb, writer.debug_info)
 end
 

src/compiler/utils.jl

@@ -322,6 +322,11 @@ mutable struct CGCtx
     # `tuple_element_source` and other parent-walking queries can start
     # from the right scope. `nothing` when no block has been entered yet.
     current_block::Any
+
+    # Set by `record_coverage!` when at least one `:code_coverage_effect` was
+    # marked for this kernel. Gates the function-definition-line coverage visit
+    # in `emit_kernel!` so untracked kernels aren't reported.
+    recorded_coverage::Bool
 end
 
 function CGCtx(; cb::CodeBuilder, tt::TypeTable, sci::StructuredIRCode,
@@ -354,6 +359,7 @@ function CGCtx(; cb::CodeBuilder, tt::TypeTable, sci::StructuredIRCode,
         nothing,                         # bounds_info — set by run_passes!
         Dict{Value, Value}(),            # assume_wrapped
         nothing,                         # current_block — set by emit_block!
+        false,                           # recorded_coverage — set by record_coverage!
     )
 end
 

test/codegen/coverage.jl

@@ -33,6 +33,22 @@
         return false
     end
 
+    # Execution count recorded for an exact line, or `nothing` if not instrumented.
+    function lcov_line_count(tracefile, file, line)
+        in_block = false
+        for l in eachline(tracefile)
+            if startswith(l, "SF:")
+                in_block = (l == "SF:" * file)
+            elseif l == "end_of_record"
+                in_block = false
+            elseif in_block && startswith(l, "DA:")
+                ln, cnt = parse.(Int, split(l[4:end], ","))
+                ln == line && return cnt
+            end
+        end
+        return nothing
+    end
+
     if Base.JLOptions().code_coverage == 0
         @test_skip "requires --code-coverage"
     else
@@ -50,6 +66,15 @@
                 m = only(methods(f))
                 @test lcov_any_covered(tracefile, string(m.file), m.line, m.line + 4)
             end
+
+            # The kernel entry's definition (signature) line specifically must be
+            # covered — the per-statement coverage effects only mark body lines, so
+            # without the prologue visit the header shows as missed (red). Use the
+            # compiled entry `cov_kernel`, not the `@inline`d `cov_only_scale` whose
+            # signature line is intentionally not marked (Julia doesn't mark it either).
+            m = only(methods(cov_kernel))
+            @test lcov_line_count(tracefile, string(m.file), m.line) !== nothing
+            @test something(lcov_line_count(tracefile, string(m.file), m.line), 0) >= 1
         end
     end
 end