From 8523ea11a677b78e1fc05915976c04b1ff081451 Mon Sep 17 00:00:00 2001 From: Aart Bik Date: Thu, 1 Jun 2017 15:45:09 -0700 Subject: Fixed bug in relying on precise FP in periodic sequence. Rationale: FP arithmetic is not always precise, so relying on FP period sequences to "compute back" precisely is not valid; when all values in the period are "fetches" however, the rotation is precise. Bug found by fuzz testing. With regression test. Bug: 62196559 Test: test-art-host Change-Id: Ie8f6b965b1921ff2762b90eebb8c20503c44c6bb --- compiler/optimizing/induction_var_range.cc | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) (limited to 'compiler/optimizing/induction_var_range.cc') diff --git a/compiler/optimizing/induction_var_range.cc b/compiler/optimizing/induction_var_range.cc index 7c833cf70c..c0ec58f824 100644 --- a/compiler/optimizing/induction_var_range.cc +++ b/compiler/optimizing/induction_var_range.cc @@ -1132,11 +1132,27 @@ bool InductionVarRange::GenerateLastValuePeriodic(HInductionVarAnalysis::Inducti /*out*/bool* needs_taken_test) const { DCHECK(info != nullptr); DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kPeriodic); - // Count period. + // Count period and detect all-invariants. int64_t period = 1; - for (HInductionVarAnalysis::InductionInfo* p = info; - p->induction_class == HInductionVarAnalysis::kPeriodic; - p = p->op_b, ++period) {} + bool all_invariants = true; + HInductionVarAnalysis::InductionInfo* p = info; + for (; p->induction_class == HInductionVarAnalysis::kPeriodic; p = p->op_b, ++period) { + DCHECK_EQ(p->op_a->induction_class, HInductionVarAnalysis::kInvariant); + if (p->op_a->operation != HInductionVarAnalysis::kFetch) { + all_invariants = false; + } + } + DCHECK_EQ(p->induction_class, HInductionVarAnalysis::kInvariant); + if (p->operation != HInductionVarAnalysis::kFetch) { + all_invariants = false; + } + // Don't rely on FP arithmetic to be precise, unless the full period + // consist of pre-computed expressions only. + if (info->type == Primitive::kPrimFloat || info->type == Primitive::kPrimDouble) { + if (!all_invariants) { + return false; + } + } // Handle any periodic(x, periodic(.., y)) for known maximum index value m. int64_t m = 0; if (IsConstant(trip->op_a, kExact, &m) && m >= 1) { -- cgit v1.2.3-59-g8ed1b