Author: hager <sven.ha...@uni-duesseldorf.de>
Branch: ppc-jit-backend
Changeset: r49301:14e77d72c41c
Date: 2011-11-11 13:20 +0100
http://bitbucket.org/pypy/pypy/changeset/14e77d72c41c/
Log: Added some comments in ppcgen/ppc_assembler.py
diff --git a/pypy/jit/backend/ppc/ppcgen/ppc_assembler.py
b/pypy/jit/backend/ppc/ppcgen/ppc_assembler.py
--- a/pypy/jit/backend/ppc/ppcgen/ppc_assembler.py
+++ b/pypy/jit/backend/ppc/ppcgen/ppc_assembler.py
@@ -74,6 +74,41 @@
EMPTY_LOC = '\xFE'
END_OF_LOCS = '\xFF'
+
+ '''
+ PyPy's PPC stack frame layout
+ =============================
+
+ . .
+ . .
+ ----------------------------
+ | BACKCHAIN | OLD FRAME
+ ------------------------------------------------------
+ | | PyPy Frame
+ | GPR SAVE AREA |
+ | |
+ ----------------------------
+ | FORCE INDEX |
+ ---------------------------- <- Spilling Pointer (SPP)
+ | |
+ | SPILLING AREA |
+ | |
+ ---------------------------- <- Stack Pointer (SP)
+
+ The size of the GPR save area and the force index area fixed:
+
+ GPR SAVE AREA: len(NONVOLATILES) * WORD
+ FORCE INDEX : WORD
+
+
+ The size of the spilling area is known when the trace operations
+ have been generated.
+ '''
+
+ GPR_SAVE_AREA_AND_FORCE_INDEX = GPR_SAVE_AREA + WORD
+ # ^^^^^^^^^^^^^ ^^^^
+ # save GRP regs force index
+
def __init__(self, cpu, failargs_limit=1000):
self.cpu = cpu
self.fail_boxes_int = values_array(lltype.Signed, failargs_limit)
@@ -124,6 +159,8 @@
clt.asmmemmgr = []
return clt.asmmemmgr_blocks
+ # The code generated here allocates a new stackframe
+ # and is the first machine code to be executed.
def _make_prologue(self, target_pos, frame_depth):
if IS_PPC_32:
# save it in previous frame (Backchain)
@@ -158,10 +195,14 @@
@rgc.no_collect
def failure_recovery_func(mem_loc, stack_pointer, spilling_pointer):
- """mem_loc is a structure in memory describing where the values for
- the failargs are stored.
- frame loc is the address of the frame pointer for the frame to be
- decoded frame """
+ """
+ mem_loc is a structure in memory describing where the values
for
+ the failargs are stored.
+
+ stack_pointer is the address of top of the stack.
+
+ spilling_pointer is the address of the FORCE_INDEX.
+ """
return self.decode_registers_and_descr(mem_loc, stack_pointer,
spilling_pointer)
self.failure_recovery_func = failure_recovery_func
@@ -289,9 +330,17 @@
return mc.materialize(self.cpu.asmmemmgr, [],
self.cpu.gc_ll_descr.gcrootmap)
+ # The code generated here serves as an exit stub from
+ # the executed machine code.
+ # It is generated only once when the backend is initialized.
+ #
+ # The following actions are performed:
+ # - The fail boxes are filled with the computed values
+ # (failure_recovery_func)
+ # - The nonvolatile registers are restored
+ # - jump back to the calling code
def _gen_exit_path(self):
mc = PPCBuilder()
- #
# compute offset to new SP
size = WORD * (len(r.MANAGED_REGS)) + BACKCHAIN_SIZE
# set SP
@@ -316,7 +365,6 @@
r2_value = descr[1]
r11_value = descr[2]
- #
# load parameters into parameter registers
if IS_PPC_32:
mc.lwz(r.r3.value, r.SPP.value, 0) # address of state encoding
@@ -328,6 +376,7 @@
# load address of decoding function into r0
mc.load_imm(r.r0, addr)
if IS_PPC_64:
+ # load TOC pointer and environment pointer
mc.load_imm(r.r2, r2_value)
mc.load_imm(r.r11, r11_value)
# ... and branch there
@@ -340,12 +389,19 @@
mc.mr(r.r5.value, r.SPP.value)
self._restore_nonvolatiles(mc, r.r5)
# load old backchain into r4
+ offset_to_old_backchain = self.GPR_SAVE_AREA_AND_FORCE_INDEX + WORD
if IS_PPC_32:
mc.lwz(r.r4.value, r.r5.value, GPR_SAVE_AREA + 2 * WORD)
else:
mc.ld(r.r4.value, r.r5.value, GPR_SAVE_AREA + 2 * WORD)
mc.mtlr(r.r4.value) # restore LR
mc.addi(r.SP.value, r.r5.value, GPR_SAVE_AREA + WORD) # restore old SP
+
+ # From SPP, we have a constant offset of GPR_SAVE_AREA_AND_FORCE_INDEX
+ # to the old backchain. We use the SPP to re-establish the old
backchain
+ # because this exit stub is generated before we know how much space
+ # the entire frame will need.
+ mc.addi(r.SP.value, r.r5.value, self.GPR_SAVE_AREA_AND_FORCE_INDEX) #
restore old SP
mc.blr()
mc.prepare_insts_blocks()
return mc.materialize(self.cpu.asmmemmgr, [],
@@ -361,6 +417,7 @@
else:
mc.std(reg.value, r.SP.value, i * WORD + BACKCHAIN_SIZE)
+ # Load parameters from fail args into locations (stack or registers)
def gen_bootstrap_code(self, nonfloatlocs, inputargs):
for i in range(len(nonfloatlocs)):
loc = nonfloatlocs[i]
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