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Enhances basic alias analysis to recognize phis whose first incoming values are NoAlias and whose other incoming values are just the phi node itself through some amount of recursion. Example: With this change basicaa reports that ptr_phi and ptr_phi2 do not alias each other. bb: ptr = ptr2 + 1 loop: ptr_phi = phi [bb, ptr], [loop, ptr_plus_one] ptr2_phi = phi [bb, ptr2], [loop, ptr2_plus_one] ... ptr_plus_one = gep ptr_phi, 1 ptr2_plus_one = gep ptr2_phi, 1 This enables the elimination of one load in code like the following: extern int foo; int test_noalias(int *ptr, int num, int* coeff) { int *ptr2 = ptr; int result = (*ptr++) * (*coeff--); while (num--) { *ptr2++ = *ptr; result += (*coeff--) * (*ptr++); } *ptr = foo; return result; } Part 2/2 of fix for PR13564. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163319 91177308-0d34-0410-b5e6-96231b3b80d8
34 lines
1.2 KiB
LLVM
34 lines
1.2 KiB
LLVM
target datalayout =
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"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
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; ptr_phi and ptr2_phi do not alias.
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; CHECK: NoAlias: i32* %ptr2_phi, i32* %ptr_phi
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define i32 @test_noalias(i32* %ptr2, i32 %count, i32* %coeff) {
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entry:
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%ptr = getelementptr inbounds i32* %ptr2, i64 1
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br label %while.body
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while.body:
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%num = phi i32 [ %count, %entry ], [ %dec, %while.body ]
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%ptr_phi = phi i32* [ %ptr, %entry ], [ %ptr_inc, %while.body ]
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%ptr2_phi = phi i32* [ %ptr2, %entry ], [ %ptr2_inc, %while.body ]
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%result.09 = phi i32 [ 0 , %entry ], [ %add, %while.body ]
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%dec = add nsw i32 %num, -1
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%0 = load i32* %ptr_phi, align 4
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store i32 %0, i32* %ptr2_phi, align 4
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%1 = load i32* %coeff, align 4
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%2 = load i32* %ptr_phi, align 4
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%mul = mul nsw i32 %1, %2
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%add = add nsw i32 %mul, %result.09
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%tobool = icmp eq i32 %dec, 0
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%ptr_inc = getelementptr inbounds i32* %ptr_phi, i64 1
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%ptr2_inc = getelementptr inbounds i32* %ptr2_phi, i64 1
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br i1 %tobool, label %the_exit, label %while.body
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the_exit:
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ret i32 %add
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}
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