From f03a23984ddaf9edab26d7b7b6cf97af876e36c8 Mon Sep 17 00:00:00 2001
From: Yiannis Tsiouris <gtsiour@softlab.ntua.gr>
Date: Thu, 27 Mar 2014 15:55:11 +0200
Subject: Fix frame size adjustment of stack descriptors

In case of function calls with arguments that are passed to the stack,
the frame size of corresponding stack descriptors needs to be reduced by
the number of stack arguments. This commit fixes a bug in this
adjustment which was caused by an incorrect check.
---
 lib/hipe/llvm/hipe_llvm_main.erl | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

(limited to 'lib/hipe')

diff --git a/lib/hipe/llvm/hipe_llvm_main.erl b/lib/hipe/llvm/hipe_llvm_main.erl
index e911fb89c9..0e50c9539b 100644
--- a/lib/hipe/llvm/hipe_llvm_main.erl
+++ b/lib/hipe/llvm/hipe_llvm_main.erl
@@ -342,8 +342,8 @@ create_sdesc_list([{ExnLbl, SPOff} | MoreExnAndSPOffs],
 %%      (thus, some of their arguments are passed to the stack). Because of the
 %%      Reserved Call Frame feature that the LLVM uses, the stack descriptors
 %%      are not correct since at the point of call the frame size is reduced
-%%      proportionally to the number of arguments that are passed on the stack.
-%%      Also the offsets of the roots need to be re-adjusted.
+%%      by the number of arguments that are passed on the stack. Also, the
+%%      offsets of the roots need to be re-adjusted.
 fix_stack_descriptors(_, _, [], _) ->
   [];
 fix_stack_descriptors(RelocsDict, Relocs, SDescs, ExposedClosures) ->
@@ -427,30 +427,22 @@ find_offsets([{Off,Arity}|Rest], Offsets, Acc) ->
   [I | RestOffsets] = lists:dropwhile(fun (Y) -> Y<Off end, Offsets),
   find_offsets(Rest, RestOffsets, [{I, Arity}|Acc]).
 
-%% The functions below correct the arity of calls, that are identified
-%% by offset, in the stack descriptors.
+%% The function below corrects the stack descriptors of calls with arguments
+%% that are passed on the stack (more than NR_ARG_REGS) by subtracting the
+%% number of stacked arguments from the frame size and from the offset of the
+%% roots.
 fix_sdescs([], SDescs) -> SDescs;
 fix_sdescs([{Offset, Arity} | Rest], SDescs) ->
   case lists:keyfind(Offset, 2, SDescs) of
     false ->
       fix_sdescs(Rest, SDescs);
-    {?SDESC, Offset, SDesc} ->
-      {ExnHandler, FrameSize, StkArity, Roots} = SDesc,
-      DecRoot = fun(X) -> X-Arity end,
-      NewRootsList = lists:map(DecRoot, tuple_to_list(Roots)),
-      NewSDesc =
-        case length(NewRootsList) > 0 andalso hd(NewRootsList) >= 0 of
-          true ->
-            {?SDESC, Offset, {ExnHandler, FrameSize-Arity, StkArity,
-			      list_to_tuple(NewRootsList)}};
-          false ->
-            {?SDESC, Offset, {ExnHandler, FrameSize, StkArity, Roots}}
-        end,
-      RestSDescs = lists:keydelete(Offset, 2, SDescs),
-      fix_sdescs(Rest, [NewSDesc | RestSDescs])
+    {?SDESC, Offset, {ExnHandler, FrameSize, StkArity, Roots}} ->
+      FixedRoots = list_to_tuple([Ri - Arity || Ri <- tuple_to_list(Roots)]),
+      FixedSDesc =
+        {?SDESC, Offset, {ExnHandler, FrameSize - Arity, StkArity, FixedRoots}},
+      fix_sdescs(Rest, [FixedSDesc | lists:keydelete(Offset, 2, SDescs)])
   end.
 
-
 %%------------------------------------------------------------------------------
 %% Miscellaneous functions
 %%------------------------------------------------------------------------------
-- 
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