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Continue by jumping to the top-of-stack after a safe foreign call

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commit f67a8b859b4b5a94d06572e24c1947af0d3f5649 1 parent 22d5822
@simonmar simonmar authored
Showing with 7 additions and 5 deletions.
  1. +7 −5 compiler/cmm/CmmLayoutStack.hs
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12 compiler/cmm/CmmLayoutStack.hs
@@ -897,7 +897,7 @@ live across the call. Our job now is to expand the call so we get
| BaseReg = resumeThread(token)
| LOAD_THREAD_STATE()
| R1 = r -- copyOut
- | jump L1
+ | jump Sp[0]
'-----------------------
L1:
r = R1 -- copyIn, inserted by mkSafeCall
@@ -928,15 +928,17 @@ lowerSafeForeignCall dflags block
mkAssign (CmmGlobal BaseReg) (CmmReg (CmmLocal new_base)) <*>
caller_load <*>
loadThreadState dflags load_tso load_stack
- -- Note: The successor must be a procpoint, and we have already split,
- -- so we use a jump, not a branch.
- succLbl = CmmLit (CmmLabel (infoTblLbl succ))
(ret_args, regs, copyout) = copyOutOflow NativeReturn Jump (Young succ)
(map (CmmReg . CmmLocal) res)
updfr (0, [])
- jump = CmmCall { cml_target = succLbl
+ -- NB. after resumeThread returns, the top-of-stack probably contains
+ -- the stack frame for succ, but it might not: if the current thread
+ -- received an exception during the call, then the stack might be
+ -- different. Hence we continue by jumping to the top stack frame,
+ -- not by jumping to succ.
+ jump = CmmCall { cml_target = CmmLoad (CmmReg spReg) bWord
, cml_cont = Just succ
, cml_args_regs = regs
, cml_args = widthInBytes wordWidth
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