[PATCH v1 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>
---
 xen/Kconfig.debug             | 9 +++++++++
 xen/Rules.mk                  | 3 +++
 xen/common/coverage/gcc_4_7.c | 4 ++++
 3 files changed, 16 insertions(+)

diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index f7cc5ffaab..7f758d221b 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_IS_CLANG
+       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
diff --git a/xen/common/coverage/gcc_4_7.c b/xen/common/coverage/gcc_4_7.c
index e3ce69dc2e..d10a16c9a8 100644
--- a/xen/common/coverage/gcc_4_7.c
+++ b/xen/common/coverage/gcc_4_7.c
@@ -43,6 +43,10 @@
 #define GCOV_UNIT_SIZE 4
 #endif
 
+#if defined(CONFIG_CONDITION_COVERAGE) && (GCC_VERSION < 140100)
+#error "GCC 14.1 or never is required to generate conditional coverage data"
+#endif
+
 static struct gcov_info *gcov_info_head;
 
 /**
-- 
2.48.1