Clean-up Makefile help

Do not show the details of the default architecture for a simple "make help"
invocation, as the details are most likely to confuse beginners. Instead we
make it clear which architecture is the default and put an example at the end
of the Makefile as an incentative to use "make help ARCH=blah" to discover
the flags used by the different architectures.

```
    make help
    make help ARCH=x86-64-ssse3
```

Also clean-up and modernize a bit the Makefile examples while at it.

closes https://github.com/official-stockfish/Stockfish/pull/2996

No functional change

diff --git a/src/Makefile b/src/Makefile
index 027cc3e3390fd7d6e2c2fa098213edc479aa1cb9..a9fb7b817da0eaae7092b4fe2d3084f13a03b399 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -81,6 +81,11 @@ endif
 # at the end of the line for flag values.
 
 ### 2.1. General and architecture defaults
+
+ifeq ($(ARCH),)
+    empty_arch = yes
+endif
+
 optimize = yes
 debug = no
 sanitize = no
@@ -99,6 +104,7 @@ neon = no
 ARCH = x86-64-modern
 
 ### 2.2 Architecture specific
+
 ifeq ($(ARCH),general-32)
        arch = any
        bits = 32
@@ -141,16 +147,7 @@ ifeq ($(ARCH),x86-64-ssse3)
        ssse3 = yes
 endif
 
-ifeq ($(ARCH),x86-64-modern)
-       arch = x86_64
-       prefetch = yes
-       popcnt = yes
-       sse = yes
-       ssse3 = yes
-       sse41 = yes
-endif
-
-ifeq ($(ARCH),x86-64-sse41-popcnt)
+ifeq ($(ARCH),$(filter $(ARCH),x86-64-sse41-popcnt x86-64-modern))
        arch = x86_64
        prefetch = yes
        popcnt = yes
@@ -535,12 +532,13 @@ help:
        @echo ""
        @echo "Supported targets:"
        @echo ""
+       @echo "help                    > Display architecture details"
        @echo "build                   > Standard build"
-       @echo "profile-build           > Standard build with PGO"
+       @echo "net                     > Download the default nnue net"
+       @echo "profile-build           > Faster build (with profile-guided optimization)"
        @echo "strip                   > Strip executable"
        @echo "install                 > Install executable"
        @echo "clean                   > Clean up"
-       @echo "net                     > Download the default nnue net"
        @echo ""
        @echo "Supported archs:"
        @echo ""
@@ -549,7 +547,7 @@ help:
        @echo "x86-64-bmi2             > x86 64-bit with bmi2 support"
        @echo "x86-64-avx2             > x86 64-bit with avx2 support"
        @echo "x86-64-sse41-popcnt     > x86 64-bit with sse41 and popcnt support"
-       @echo "x86-64-modern           > the same as previous (x86-64-sse41-popcnt)"
+       @echo "x86-64-modern           > common modern CPU, currently x86-64-sse41-popcnt"
        @echo "x86-64-ssse3            > x86 64-bit with ssse3 support"
        @echo "x86-64-sse3-popcnt      > x86 64-bit with sse3 and popcnt support"
        @echo "x86-64                  > x86 64-bit generic"
@@ -572,17 +570,20 @@ help:
        @echo ""
        @echo "Simple examples. If you don't know what to do, you likely want to run: "
        @echo ""
-       @echo "make -j build ARCH=x86-64    (This is for 64-bit systems)"
-       @echo "make -j build ARCH=x86-32    (This is for 32-bit systems)"
+       @echo "make -j build ARCH=x86-64  (A portable, slow compile for 64-bit systems)"
+       @echo "make -j build ARCH=x86-32  (A portable, slow compile for 32-bit systems)"
        @echo ""
-       @echo "Advanced examples, for experienced users: "
+       @echo "Advanced examples, for experienced users looking for performance: "
        @echo ""
-       @echo "make -j build ARCH=x86-64-modern COMP=clang"
-       @echo "make -j profile-build ARCH=x86-64-bmi2 COMP=gcc COMPCXX=g++-4.8"
-       @echo ""
-       @echo "The selected architecture $(ARCH) enables the following configuration: "
+       @echo "make    help  ARCH=x86-64-bmi2"
+       @echo "make -j profile-build ARCH=x86-64-bmi2 COMP=gcc COMPCXX=g++-9.0"
+       @echo "make -j build ARCH=x86-64-ssse3 COMP=clang"
        @echo ""
+ifneq ($(empty_arch), yes)
+       @echo "-------------------------------\n"
+       @echo "The selected architecture $(ARCH) will enable the following configuration: "
        @$(MAKE) ARCH=$(ARCH) COMP=$(COMP) config-sanity
+endif
 
 
 .PHONY: help build profile-build strip install clean net objclean profileclean \