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VM: endless loop prevention

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This commit is contained in:
Araq 2014-03-24 08:43:57 +01:00
commit ee1192679e
4 changed files with 33 additions and 1213 deletions
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14
compiler/vmgen.nim
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@ -92,10 +92,10 @@ proc genLabel(c: PCtx): TPosition =
result = TPosition(c.code.len)
#c.jumpTargets.incl(c.code.len)
proc jmpBack(c: PCtx, n: PNode, opc: TOpcode, p = TPosition(0)) =
proc jmpBack(c: PCtx, n: PNode, p = TPosition(0)) =
let dist = p.int - c.code.len
internalAssert(-0x7fff < dist and dist < 0x7fff)
gABx(c, n, opc, 0, dist)
gABx(c, n, opcJmpBack, 0, dist)
proc patch(c: PCtx, p: TPosition) =
# patch with current index
@ -229,20 +229,20 @@ proc genWhile(c: PCtx; n: PNode) =
withBlock(nil):
if isTrue(n.sons[0]):
c.gen(n.sons[1])
c.jmpBack(n, opcJmp, L1)
c.jmpBack(n, L1)
elif isNotOpr(n.sons[0]):
var tmp = c.genx(n.sons[0].sons[1])
let L2 = c.xjmp(n, opcTJmp, tmp)
c.freeTemp(tmp)
c.gen(n.sons[1])
c.jmpBack(n, opcJmp, L1)
c.jmpBack(n, L1)
c.patch(L2)
else:
var tmp = c.genx(n.sons[0])
let L2 = c.xjmp(n, opcFJmp, tmp)
c.freeTemp(tmp)
c.gen(n.sons[1])
c.jmpBack(n, opcJmp, L1)
c.jmpBack(n, L1)
c.patch(L2)
proc genBlock(c: PCtx; n: PNode; dest: var TDest) =
@ -1518,7 +1518,7 @@ proc optimizeJumps(c: PCtx; start: int) =
var d = i + c.code[i].jmpDiff
for iters in countdown(maxIterations, 0):
case c.code[d].opcode
of opcJmp:
of opcJmp, opcJmpBack:
d = d + c.code[d].jmpDiff
of opcTJmp, opcFJmp:
if c.code[d].regA != reg: break
@ -1536,7 +1536,7 @@ proc optimizeJumps(c: PCtx; start: int) =
else: break
if d != i + c.code[i].jmpDiff:
c.finalJumpTarget(i, d - i)
of opcJmp:
of opcJmp, opcJmpBack:
var d = i + c.code[i].jmpDiff
var iters = maxIterations
while c.code[d].opcode == opcJmp and iters > 0: