JIT: Optimize zero inits out only for locals that aren't candidates to be tracked (#82042)

jakobbotsch · web-flow · commit 8a96ee761d45 · 2023-02-14T12:21:41.000+01:00
Otherwise we may track it after lowering and invalidate the assumptions made by the optimization. Fix #82020
diff --git a/src/coreclr/jit/optimizer.cpp b/src/coreclr/jit/optimizer.cpp
@@ -10344,10 +10344,13 @@ void Compiler::optRemoveRedundantZeroInits()
 
                             if (!bbInALoop || bbIsReturn)
                             {
+                                bool neverTracked = lclDsc->IsAddressExposed() || lclDsc->lvPinned ||
+                                                    (lclDsc->lvPromoted && varTypeIsStruct(lclDsc));
+
                                 if (BitVecOps::IsMember(&bitVecTraits, zeroInitLocals, lclNum) ||
                                     (lclDsc->lvIsStructField &&
                                      BitVecOps::IsMember(&bitVecTraits, zeroInitLocals, lclDsc->lvParentLcl)) ||
-                                    ((!lclDsc->lvTracked || !isEntire) &&
+                                    ((neverTracked || !isEntire) &&
                                      !fgVarNeedsExplicitZeroInit(lclNum, bbInALoop, bbIsReturn)))
                                 {
                                     // We are guaranteed to have a zero initialization in the prolog or a

Original file line number	Diff line number	Diff line change
`@@ -10344,10 +10344,13 @@ void Compiler::optRemoveRedundantZeroInits()`
`10344`	`10344`
`10345`	`10345`	`if (!bbInALoop \|\| bbIsReturn)`
`10346`	`10346`	`{`
	`10347`	`+ bool neverTracked = lclDsc->IsAddressExposed() \|\| lclDsc->lvPinned \|\|`
	`10348`	`+ (lclDsc->lvPromoted && varTypeIsStruct(lclDsc));`
	`10349`	`+`
`10347`	`10350`	`if (BitVecOps::IsMember(&bitVecTraits, zeroInitLocals, lclNum) \|\|`
`10348`	`10351`	`(lclDsc->lvIsStructField &&`
`10349`	`10352`	`BitVecOps::IsMember(&bitVecTraits, zeroInitLocals, lclDsc->lvParentLcl)) \|\|`
`10350`		`- ((!lclDsc->lvTracked \|\| !isEntire) &&`
	`10353`	`+ ((neverTracked \|\| !isEntire) &&`
`10351`	`10354`	`!fgVarNeedsExplicitZeroInit(lclNum, bbInALoop, bbIsReturn)))`
`10352`	`10355`	`{`
`10353`	`10356`	`// We are guaranteed to have a zero initialization in the prolog or a`