ARM backend contribution from Apple.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33353 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/Target/ARM/README-Thumb.txt b/lib/Target/ARM/README-Thumb.txt
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+//===---------------------------------------------------------------------===//
+// Random ideas for the ARM backend (Thumb specific).
+//===---------------------------------------------------------------------===//
+
+* Add support for compiling functions in both ARM and Thumb mode, then taking
+  the smallest.
+* Add support for compiling individual basic blocks in thumb mode, when in a 
+  larger ARM function.  This can be used for presumed cold code, like paths
+  to abort (failure path of asserts), EH handling code, etc.
+
+* Thumb doesn't have normal pre/post increment addressing modes, but you can
+  load/store 32-bit integers with pre/postinc by using load/store multiple
+  instrs with a single register.
+
+* Make better use of high registers r8, r10, r11, r12 (ip). Some variants of add
+  and cmp instructions can use high registers. Also, we can use them as
+  temporaries to spill values into.