Author: Armin Rigo <[email protected]>
Branch: jitypes2
Changeset: r44200:ee22edbf20e8
Date: 2011-05-16 12:07 +0200
http://bitbucket.org/pypy/pypy/changeset/ee22edbf20e8/
Log: A comment.
diff --git a/pypy/jit/backend/x86/regalloc.py b/pypy/jit/backend/x86/regalloc.py
--- a/pypy/jit/backend/x86/regalloc.py
+++ b/pypy/jit/backend/x86/regalloc.py
@@ -774,6 +774,19 @@
self.xrm.possibly_free_var(op.getarg(1))
def _call(self, op, arglocs, force_store=[], guard_not_forced_op=None):
+ # we need to save registers on the stack:
+ #
+ # - at least the non-callee-saved registers
+ #
+ # - for shadowstack, we assume that any call can collect, and we
+ # save also the callee-saved registers that contain GC pointers,
+ # so that they can be found by follow_stack_frame_of_assembler()
+ #
+ # - for CALL_MAY_FORCE or CALL_ASSEMBLER, we have to save all regs
+ # anyway, in case we need to do cpu.force(). The issue is that
+ # grab_frame_values() would not be able to locate values in
+ # callee-saved registers.
+ #
save_all_regs = guard_not_forced_op is not None
self.xrm.before_call(force_store, save_all_regs=save_all_regs)
if not save_all_regs:
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