Overhauled llvm/clang docs builds. Closes PR6613.

NOTE: 2nd part changeset for cfe trunk to follow.

*** PRE-PATCH ISSUES ADDRESSED

- clang api docs fail build from objdir
- clang/llvm api docs collide in install PREFIX/
- clang/llvm main docs collide in install
- clang/llvm main docs have full of hard coded destination
  assumptions and make use of absolute root in static html files;
  namely CommandGuide tools hard codes a website destination
  for cross references and some html cross references assume
  website root paths

*** IMPROVEMENTS

- bumped Doxygen from 1.4.x -> 1.6.3
- splits llvm/clang docs into 'main' and 'api' (doxygen) build trees
- provide consistent, reliable doc builds for both main+api docs
- support buid vs. install vs. website intentions
- support objdir builds
- document targets with 'make help'
- correct clean and uninstall operations
- use recursive dir delete only where absolutely necessary
- added call function fn.RMRF which safeguards against botched 'rm -rf';
  if any target (or any variable is evaluated) which attempts
  to remove any dirs which match a hard-coded 'safelist', a verbose
  error will be printed and make will error-stop.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103213 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 0 deletions

diff --git a/docs/main/HistoricalNotes/2001-07-06-LoweringIRForCodeGen.txt b/docs/main/HistoricalNotes/2001-07-06-LoweringIRForCodeGen.txt
new file mode 100644
index 0000000000..3e10416fe6
--- /dev/null
+++ b/docs/main/HistoricalNotes/2001-07-06-LoweringIRForCodeGen.txt
@@ -0,0 +1,31 @@
+Date: Fri, 6 Jul 2001 16:56:56 -0500
+From: Vikram S. Adve <vadve@cs.uiuc.edu>
+To: Chris Lattner <lattner@cs.uiuc.edu>
+Subject: lowering the IR
+
+BTW, I do think that we should consider lowering the IR as you said.  I
+didn't get time to raise it today, but it comes up with the SPARC
+move-conditional instruction.  I don't think we want to put that in the core
+VM -- it is a little too specialized.  But without a corresponding
+conditional move instruction in the VM, it is pretty difficult to maintain a
+close mapping between VM and machine code.  Other architectures may have
+other such instructions.
+
+What I was going to suggest was that for a particular processor, we define
+additional VM instructions that match some of the unusual opcodes on the
+processor but have VM semantics otherwise, i.e., all operands are in SSA
+form and typed.  This means that we can re-generate core VM code from the
+more specialized code any time we want (so that portability is not lost).
+
+Typically, a static compiler like gcc would generate just the core VM, which
+is relatively portable.  Anyone (an offline tool, the linker, etc., or even
+the static compiler itself if it chooses) can transform that into more
+specialized target-specific VM code for a particular architecture.  If the
+linker does it, it can do it after all machine-independent optimizations.
+This would be the most convenient, but not necessary.
+
+The main benefit of lowering will be that we will be able to retain a close
+mapping between VM and machine code.
+
+--Vikram
+