toolchain-funcs.eclass: Add tc-get-compiler-type()

Add a tc-get-compiler-type() function that can be used to identify
the compiler being used, using the preprocessor defines. Alike
gcc-*version() routines, it uses CPP (which in turn uses CC).

The major usage would be applying compiler-specific quirks and limiting
gcc version checks to compilers that actually are gcc, since e.g. clang
reports gcc version 4.2 -- which would incorrectly cause numerous gcc
version checks in ebuilds to fail.

eclass/tests/toolchain-funcs.sh

@@ -111,5 +111,45 @@ tc-ld-disable-gold
 )
 tend $?
 
+unset CPP
+
+tbegin "tc-get-compiler-type (gcc)"
+(
+export CC=gcc
+[[ $(tc-get-compiler-type) == gcc ]]
+)
+tend $?
+
+if type -P clang &>/dev/null; then
+	tbegin "tc-get-compiler-type (clang)"
+	(
+	export CC=clang
+	[[ $(tc-get-compiler-type) == clang ]]
+	)
+	tend $?
+fi
+
+if type -P pathcc &>/dev/null; then
+	tbegin "tc-get-compiler-type (pathcc)"
+	(
+	export CC=pathcc
+	[[ $(tc-get-compiler-type) == pathcc ]]
+	)
+	tend $?
+
+	tbegin "! tc-is-gcc (pathcc)"
+	(
+	export CC=pathcc
+	! tc-is-gcc
+	)
+	tend $?
+
+	tbegin "! tc-is-clang (pathcc)"
+	(
+	export CC=pathcc
+	! tc-is-clang
+	)
+	tend $?
+fi
 
 texit

eclass/toolchain-funcs.eclass

@@ -585,6 +585,28 @@ tc-endian() {
 	esac
 }
 
+# @FUNCTION: tc-get-compiler-type
+# @RETURN: keyword identifying the compiler: gcc, clang, pathcc, unknown
+tc-get-compiler-type() {
+	local code='
+#if defined(__PATHSCALE__)
+	HAVE_PATHCC
+#elif defined(__clang__)
+	HAVE_CLANG
+#elif defined(__GNUC__)
+	HAVE_GCC
+#endif
+'
+	local res=$($(tc-getCPP "$@") -E -P - <<<"${code}")
+
+	case ${res} in
+		*HAVE_PATHCC*)	echo pathcc;;
+		*HAVE_CLANG*)	echo clang;;
+		*HAVE_GCC*)		echo gcc;;
+		*)				echo unknown;;
+	esac
+}
+
 # Internal func.  The first argument is the version info to expand.
 # Query the preprocessor to improve compatibility across different
 # compilers rather than maintaining a --version flag matrix. #335943