[PATCH v3 3/3] xen: debug: gcov: add condition coverage support

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

Condition coverage, also known as MC/DC (modified condition/decision
coverage) is a coverage metric that tracks separate outcomes in
boolean expressions.

This patch adds CONFIG_CONDITION_COVERAGE option to enable MC/DC for
GCC. Clang is not supported right now.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>

---

Changes in v3:
 - Introduced CC_HAS_MCDC that checks if compiler supports
   required feature
Changes in v2:
 - Move gcc version check from .c file to Rules.mk (I can't find
   an easy way to check GCC version at Kconfig level)
 - Check for gcc 14, not gcc 14.1
---
 xen/Kconfig       | 5 +++++
 xen/Kconfig.debug | 9 +++++++++
 xen/Rules.mk      | 3 +++
 3 files changed, 17 insertions(+)

diff --git a/xen/Kconfig b/xen/Kconfig
index 2128f0ccfc..2bdebfc808 100644
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -41,6 +41,11 @@ config CC_SPLIT_SECTIONS
 config CC_HAS_UBSAN
        def_bool $(cc-option,-fsanitize=undefined)
 
+# Compiler supports -fcondition-coverage aka MC/DC
+config CC_HAS_MCDC
+       def_bool $(cc-option,-fcondition-coverage)
+
+
 # Set code alignment.
 #
 # Allow setting on a boolean basis, and then convert such selection to an
diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index f7cc5ffaab..f89cbd823b 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -44,6 +44,15 @@ config COVERAGE
 
          If unsure, say N here.
 
+config CONDITION_COVERAGE
+       bool "Condition coverage support"
+       depends on COVERAGE && CC_HAS_MCDC
+       help
+         Enable condition coverage support. Used for collecting MC/DC
+         (Modified Condition/Decision Coverage) metrics.
+
+         If unsure, say N here.
+
 config DEBUG_LOCK_PROFILE
        bool "Lock Profiling"
        select DEBUG_LOCKS
diff --git a/xen/Rules.mk b/xen/Rules.mk
index d759cccee3..0a2933cffa 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -138,6 +138,9 @@ ifeq ($(CONFIG_CC_IS_CLANG),y)
     COV_FLAGS := -fprofile-instr-generate -fcoverage-mapping
 else
     COV_FLAGS := -fprofile-arcs -ftest-coverage
+ifeq ($(CONFIG_CONDITION_COVERAGE),y)
+    COV_FLAGS += -fcondition-coverage
+endif
 endif
 
 # Reset COV_FLAGS in cases where an objects has another one as prerequisite
-- 
2.48.1