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InstCombine: Fix a crash in Descale for multiply-by-zero
Fix a crash in `InstCombiner::Descale()` when a multiply-by-zero gets created as an argument to a GEP partway through an iteration, causing -instcombine to optimize the GEP before the multiply. rdar://problem/17615671 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212742 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1120,6 +1120,12 @@ Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) {
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return nullptr;
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}
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// If Op is zero then Val = Op * Scale.
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if (match(Op, m_Zero())) {
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NoSignedWrap = true;
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return Op;
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}
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// We know that we can successfully descale, so from here on we can safely
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// modify the IR. Op holds the descaled version of the deepest term in the
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// expression. NoSignedWrap is 'true' if multiplying Op by Scale is known
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21
test/Transforms/InstCombine/descale-zero.ll
Normal file
21
test/Transforms/InstCombine/descale-zero.ll
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@ -0,0 +1,21 @@
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; RUN: opt < %s -instcombine -S | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.10.0"
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define internal i8* @descale_zero() {
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entry:
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; CHECK: load i16** inttoptr (i64 48 to i16**), align 16
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; CHECK-NEXT: bitcast i16*
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; CHECK-NEXT: ret i8*
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%i16_ptr = load i16** inttoptr (i64 48 to i16**), align 16
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%num = load i64* inttoptr (i64 64 to i64*), align 64
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%num_times_2 = shl i64 %num, 1
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%num_times_2_plus_4 = add i64 %num_times_2, 4
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%i8_ptr = bitcast i16* %i16_ptr to i8*
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%i8_ptr_num_times_2_plus_4 = getelementptr i8* %i8_ptr, i64 %num_times_2_plus_4
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%num_times_neg2 = mul i64 %num, -2
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%num_times_neg2_minus_4 = add i64 %num_times_neg2, -4
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%addr = getelementptr i8* %i8_ptr_num_times_2_plus_4, i64 %num_times_neg2_minus_4
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ret i8* %addr
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}
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