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Safely implement strict TBAA rules.

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This fixes type punning issues with unsafeBitCast.

The optimizer is still too aggressive with UnsafePointer. To fix that,
we first need an explicit API for circumventing type safety
(rdar://23406272).

I should be able to fix the following regressions by migrating the
stdlib away from unsafeBitCast to unsafeReferenceCast (~2 weeks).

Slowdowns:
|.Benchmark.................|..Before.|...After.|.Speedup|
|.ArrayInClass..............|...49.00.|...78.00.|.-37.2%.|
|.Sim2DArray................|..471.00.|..549.00.|.-14.2%.|
|.PrimeNum..................|.1876.00.|.1980.00.|..-5.3%.|

Speedups:
|.Benchmark.................|..Before.|...After.|.Speedup|
|.HeapSort..................|.2962.00.|.2663.00.|..11.2%.|
|.StdlibSort................|.2672.00.|.2537.00.|...5.3%.|
This commit is contained in:
Andrew Trick
2015-11-10 09:20:31 -08:00
parent d326c8e5f7
commit 3d5c4969a0
8 changed files with 142 additions and 62 deletions
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5
lib/SIL/SILValue.cpp
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@@ -98,8 +98,9 @@ SILValue SILValue::stripCasts() {
V = stripSinglePredecessorArgs(V);
auto K = V->getKind();
if (isRCIdentityPreservingCast(K) ||
K == ValueKind::UncheckedTrivialBitCastInst) {
if (isRCIdentityPreservingCast(K)
|| K == ValueKind::UncheckedTrivialBitCastInst
|| K == ValueKind::MarkDependenceInst) {
V = cast<SILInstruction>(V.getDef())->getOperand(0);
continue;
}