leave the prototype to git history

1 files changed, 0 insertions, 54 deletions

diff --git a/proto/TODO b/proto/TODO
deleted file mode 100644
index e144c66..0000000
--- a/proto/TODO
+++ /dev/null
@@ -1,54 +0,0 @@
-Features
-- Operand classes for instructions
-- Hints in register allocation
-- Fixed register instructions (div, mul)
-  Is this part of "operand classes"?
-
-Instructions
-- ADD SUB SDIV UDIV SREM UREM MUL LSL LSR ASL ASR
-- SEXT ZEXT (we need 8, 16, 32, 64 bits)
-- CMP ...
-- ALLOC STORE LOAD (we need 8, 16, 32, 64 bits)
-(- PTR)
-- CALL BRZ JMP RET
-
-Machine
-- SREG GREG
-- Register use/defs for all instructions.
-
-Types
-- Integer (32 & 64 bits)
-(- Structure "{a,b,c}")
-(- Pointer (to type "t"))
-
-Questions
-- Q: Should we allow constant operands?
-  A:
-  It looks like `Con instructions are a bad idea because
-  they introduce spurious live ranges.
-  This was not a huge problem, modifications s in loc and
-  getreg only fixed this.  Still, it makes use larger bit
-  vectors during the liveness analysis.
-- Q: How to represent the IR?
-  A:
-  So far, a graph of basic blocks composed of quadruples
-  seems to be the most convenient.
-- Q: Do we need types?
-
-Problems
-- x = y op z [fixed using freeze]
-  if x is spilled, y can be moved to a spill location
-  to free one register for x, this is kind of stupid.
-  We can probably fix this by having a better heuristic
-  for spilling decisions.
-- [tentative fix: 4fc98da]
-  Phi defined variables with spill location do not work.
-- At the end of a block we call loc on all live variables,
-  if there are not enough registers, some variables get
-  assigned spill locations.  We need to be able to spill
-  variables that are already in register.
-  NOTE: Following Braun & Hack we could do one pass
-  first that determines what variables are in register
-  at the end of loops.  This sounds good because
-  back-edges are actually easier to detect than loop
-  headers!