7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 58 insertions, 0 deletions

diff --git a/linux/texture.mu b/linux/texture.mu
new file mode 100644
index 00000000..4cfd3bbe
--- /dev/null
+++ b/linux/texture.mu
@@ -0,0 +1,58 @@
+# Playing with emitting cool textures.
+#
+# To run (on Linux):
+#   $ git clone https://github.com/akkartik/mu
+#   $ cd mu
+#   $ ./translate_mu apps/texture.mu
+#   $ ./a.elf > a.ppm
+
+fn main -> _/ebx: int {
+#?   var width/esi: int <- copy 0x190  # 400
+#?   var height/edi: int <- copy 0xe1  # 225; aspect ratio 16:9
+  var width/esi: int <- copy 0xff
+  var height/edi: int <- copy 0xff
+  print-string 0/screen, "P3\n"
+  print-int32-decimal 0/screen, width
+  print-string 0/screen, " "
+  print-int32-decimal 0/screen, height
+  print-string 0/screen, "\n"
+  print-string 0/screen, "255\n"  # color depth
+  var row/ecx: int <- copy 0
+  {
+    compare row, height
+    break-if->=
+    var col/edx: int <- copy 0
+    {
+      compare col, width
+      break-if->=
+      # r
+      var tmp/eax: int <- copy col
+      tmp <- multiply row
+      tmp <- and 0x7f
+      tmp <- add 0x80
+      tmp <- copy 0xff
+      print-int32-decimal 0/screen, tmp
+      print-string 0/screen, " "
+      # g
+      tmp <- copy row
+      tmp <- multiply col
+      tmp <- and 0x7f
+      tmp <- add 0x80
+#?       tmp <- copy 0xcf
+      print-int32-decimal 0/screen, tmp
+      print-string 0/screen, " "
+      # b
+      tmp <- copy row
+      tmp <- multiply col
+      tmp <- and 0x7f
+      tmp <- add 0x80
+      print-int32-decimal 0/screen, tmp
+      print-string 0/screen, "\n"
+      col <- increment
+      loop
+    }
+    row <- increment
+    loop
+  }
+  return 0
+}