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fixes #19615; emit better code for integer divisions when the divisor… (#19626)

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* fixes #19615; emit better code for integer divisions when the divisor is known at compile-time

* proper bugfix: unsigned numbers cannot be -1
This commit is contained in:
Andreas Rumpf 2022-03-22 15:36:49 +01:00 • committed by GitHub
commit c4a0d4c5e3
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1 changed files with 16 additions and 6 deletions
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22
compiler/ccgexprs.nim
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@ -584,13 +584,23 @@ proc binaryArithOverflow(p: BProc, e: PNode, d: var TLoc, m: TMagic) =
else: else:
# we handle div by zero here so that we know that the compilerproc's # we handle div by zero here so that we know that the compilerproc's
# result is only for overflows. # result is only for overflows.
var needsOverflowCheck = true
if m in {mDivI, mModI}: if m in {mDivI, mModI}:
linefmt(p, cpsStmts, "if ($1 == 0){ #raiseDivByZero(); $2}$n", var canBeZero = true
[rdLoc(b), raiseInstr(p)]) if e[2].kind in {nkIntLit..nkUInt64Lit}:
canBeZero = e[2].intVal == 0
let res = binaryArithOverflowRaw(p, t, a, b, if e[2].kind in {nkIntLit..nkInt64Lit}:
if t.kind == tyInt64: prc64[m] else: prc[m]) needsOverflowCheck = e[2].intVal == -1
putIntoDest(p, d, e, "($#)($#)" % [getTypeDesc(p.module, e.typ), res]) if canBeZero:
linefmt(p, cpsStmts, "if ($1 == 0){ #raiseDivByZero(); $2}$n",
[rdLoc(b), raiseInstr(p)])
if needsOverflowCheck:
let res = binaryArithOverflowRaw(p, t, a, b,
if t.kind == tyInt64: prc64[m] else: prc[m])
putIntoDest(p, d, e, "($#)($#)" % [getTypeDesc(p.module, e.typ), res])
else:
let res = "($1)($2 $3 $4)" % [getTypeDesc(p.module, e.typ), rdLoc(a), rope(opr[m]), rdLoc(b)]
putIntoDest(p, d, e, res)
proc unaryArithOverflow(p: BProc, e: PNode, d: var TLoc, m: TMagic) = proc unaryArithOverflow(p: BProc, e: PNode, d: var TLoc, m: TMagic) =
var var