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Rework exception handling in the VM (#10544)

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* Rework exception handling in the VM

Make the safepoint handling more precise and less forgiving.
The new code is clearer and more commented.
Perform cleanup on `return`.
The no-exception-thrown case in a try block should be slightly faster
since we don't parse the whole set of exceptions every time.
More tests.

* Fix silly error that broke a few tests

* Testament doesn't like files having the same name

* Remove test case that failed compilation to js
This commit is contained in:
LemonBoy 2019-02-08 11:57:47 +01:00 • committed by Andreas Rumpf
commit 710cfcecd3
4 changed files with 238 additions and 106 deletions
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24
compiler/vmgen.nim
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@ -83,9 +83,12 @@ proc codeListing(c: PCtx, result: var string, start=0; last = -1) =
elif opc < firstABxInstr:
result.addf("\t$#\tr$#, r$#, r$#", opc.toStr, x.regA,
x.regB, x.regC)
elif opc in relativeJumps:
elif opc in relativeJumps + {opcTry}:
result.addf("\t$#\tr$#, L$#", opc.toStr, x.regA,
i+x.regBx-wordExcess)
elif opc in {opcExcept}:
let idx = x.regBx-wordExcess
result.addf("\t$#\t$#, $#", opc.toStr, x.regA, $idx)
elif opc in {opcLdConst, opcAsgnConst}:
let idx = x.regBx-wordExcess
result.addf("\t$#\tr$#, $# ($#)", opc.toStr, x.regA,
@ -480,10 +483,13 @@ proc genType(c: PCtx; typ: PType): int =
proc genTry(c: PCtx; n: PNode; dest: var TDest) =
if dest < 0 and not isEmptyType(n.typ): dest = getTemp(c, n.typ)
var endings: seq[TPosition] = @[]
let elsePos = c.xjmp(n, opcTry, 0)
let ehPos = c.xjmp(n, opcTry, 0)
c.gen(n.sons[0], dest)
c.clearDest(n, dest)
c.patch(elsePos)
# Add a jump past the exception handling code
endings.add(c.xjmp(n, opcJmp, 0))
# This signals where the body ends and where the exception handling begins
c.patch(ehPos)
for i in 1 ..< n.len:
let it = n.sons[i]
if it.kind != nkFinally:
@ -499,14 +505,14 @@ proc genTry(c: PCtx; n: PNode; dest: var TDest) =
c.gABx(it, opcExcept, 0, 0)
c.gen(it.lastSon, dest)
c.clearDest(n, dest)
if i < sonsLen(n)-1:
if i < sonsLen(n):
endings.add(c.xjmp(it, opcJmp, 0))
c.patch(endExcept)
for endPos in endings: c.patch(endPos)
let fin = lastSon(n)
# we always generate an 'opcFinally' as that pops the safepoint
# from the stack
# from the stack if no exception is raised in the body.
c.gABx(fin, opcFinally, 0, 0)
for endPos in endings: c.patch(endPos)
if fin.kind == nkFinally:
c.gen(fin.sons[0])
c.clearDest(n, dest)
@ -2214,9 +2220,9 @@ proc genProc(c: PCtx; s: PSym): int =
c.gABC(body, opcEof, eofInstr.regA)
c.optimizeJumps(result)
s.offset = c.prc.maxSlots
#if s.name.s == "calc":
# echo renderTree(body)
# c.echoCode(result)
# if s.name.s == "fun1":
# echo renderTree(body)
# c.echoCode(result)
c.prc = oldPrc
else:
c.prc.maxSlots = s.offset