[PATCH v2 3/5] Makefile.compiler: replace cc-ifversion with compiler-specific macros

[Nick Desaulniers <ndesaulniers@google.com>]

cc-ifversion is GCC specific. Replace it with compiler specific
variants. Update the users of cc-ifversion to use these new macros.
Provide a helper for checking compiler versions for GCC and Clang
simultaneously, that will be used in a follow up patch.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Link: https://github.com/ClangBuiltLinux/linux/issues/350
Link: https://lore.kernel.org/llvm/CAGG=3QWSAUakO42kubrCap8fp-gm1ERJJAYXTnP1iHk_wrH=BQ@mail.gmail.com/
Suggested-by: Bill Wendling <morbo@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Changes v1 -> v2:
* New patch.

 Documentation/kbuild/makefiles.rst          | 44 +++++++++++++++------
 Makefile                                    |  4 +-
 drivers/gpu/drm/amd/display/dc/dml/Makefile | 12 ++----
 scripts/Makefile.compiler                   | 15 +++++--
 4 files changed, 49 insertions(+), 26 deletions(-)

diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 11a296e52d68..e46f5b45c422 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -682,22 +682,42 @@ more details, with real examples.
 	In the above example, -Wno-unused-but-set-variable will be added to
 	KBUILD_CFLAGS only if gcc really accepts it.
 
-    cc-ifversion
-	cc-ifversion tests the version of $(CC) and equals the fourth parameter
-	if version expression is true, or the fifth (if given) if the version
-	expression is false.
+    gcc-min-version
+	gcc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater than
+	or equal to the provided value and evaluates to y if so.
 
 	Example::
 
-		#fs/reiserfs/Makefile
-		ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
+		cflags-$(call gcc-min-version, 70100) := -foo
 
-	In this example, ccflags-y will be assigned the value -O1 if the
-	$(CC) version is less than 4.2.
-	cc-ifversion takes all the shell operators:
-	-eq, -ne, -lt, -le, -gt, and -ge
-	The third parameter may be a text as in this example, but it may also
-	be an expanded variable or a macro.
+	In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
+	$(CONFIG_GCC_VERSION) is >= 7.1.
+
+    clang-min-version
+	clang-min-version tests if the value of $(CONFIG_CLANG_VERSION) is greater
+	than or equal to the provided value and evaluates to y if so.
+
+	Example::
+
+		cflags-$(call clang-min-version, 110000) := -foo
+
+	In this example, cflags-y will be assigned the value -foo if $(CC) is clang
+	and $(CONFIG_CLANG_VERSION) is >= 11.0.0.
+
+    cc-min-version
+	cc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater
+	than or equal to the first value provided, or if the value of
+	$(CONFIG_CLANG_VERSION) is greater than or equal to the second value
+	provided, and evaluates
+	to y if so.
+
+	Example::
+
+		cflags-$(call cc-min-version, 70100, 110000) := -foo
+
+	In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
+	$(CONFIG_GCC_VERSION) is >= 7.1, or if $(CC) is clang and
+	$(CONFIG_CLANG_VERSION) is >= 11.0.0.
 
     cc-cross-prefix
 	cc-cross-prefix is used to check if there exists a $(CC) in path with
diff --git a/Makefile b/Makefile
index 952d354069a4..caa39ecb1136 100644
--- a/Makefile
+++ b/Makefile
@@ -972,7 +972,7 @@ ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS += -Wno-maybe-uninitialized
 endif
 
-ifdef CONFIG_CC_IS_GCC
+ifeq ($(call gcc-min-version, 90100),y)
 # The allocators already balk at large sizes, so silence the compiler
 # warnings for bounds checks involving those possible values. While
 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
@@ -984,7 +984,7 @@ ifdef CONFIG_CC_IS_GCC
 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
 # choice, we must perform a versioned check to disable this warning.
 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
-KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0901, -Wno-alloc-size-larger-than)
+KBUILD_CFLAGS += -Wno-alloc-size-larger-than
 endif
 
 # disable invalid "can't wrap" optimizations for signed / pointers
diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
index 86a3b5bfd699..d8ee4743b2e3 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
@@ -33,20 +33,14 @@ ifdef CONFIG_PPC64
 dml_ccflags := -mhard-float -maltivec
 endif
 
-ifdef CONFIG_CC_IS_GCC
-ifeq ($(call cc-ifversion, -lt, 0701, y), y)
-IS_OLD_GCC = 1
-endif
-endif
-
 ifdef CONFIG_X86
-ifdef IS_OLD_GCC
+ifeq ($(call gcc-min-version, 70100),y)
+dml_ccflags += -msse2
+else
 # Stack alignment mismatch, proceed with caution.
 # GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
 # (8B stack alignment).
 dml_ccflags += -mpreferred-stack-boundary=4
-else
-dml_ccflags += -msse2
 endif
 endif
 
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index d1739f0d3ce3..13dade724fa3 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -61,9 +61,18 @@ cc-option-yn = $(call try-run,\
 cc-disable-warning = $(call try-run,\
 	$(CC) -Werror $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
 
-# cc-ifversion
-# Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
-cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || echo $(4))
+# gcc-min-version
+# Usage: cflags-$(call gcc-min-version, 70100) += -foo
+gcc-min-version = $(shell [ $(CONFIG_GCC_VERSION) -ge $(1) ] && echo y)
+
+# clang-min-version
+# Usage: cflags-$(call clang-min-version, 110000) += -foo
+clang-min-version = $(shell [ $(CONFIG_CLANG_VERSION) -ge $(1) ] && echo y)
+
+# cc-min-version
+# Usage: cflags-$(call cc-min-version, 701000, 110000)
+#                                      ^ GCC   ^ Clang
+cc-min-version = $(filter y, $(call gcc-min-version, $(1)), $(call clang-min-version, $(2)))
 
 # ld-option
 # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
-- 
2.37.2.672.g94769d06f0-goog