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https://github.com/c64scene-ar/llvm-6502.git
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160f9b9c10
Prior to this change, the loop vectorizer did not make use of the alias
analysis infrastructure. Instead, it performed memory dependence analysis using
ScalarEvolution-based linear dependence checks within equivalence classes
derived from the results of ValueTracking's GetUnderlyingObjects.
Unfortunately, this meant that:
1. The loop vectorizer had logic that essentially duplicated that in BasicAA
for aliasing based on identified objects.
2. The loop vectorizer could not partition the space of dependency checks
based on information only easily available from within AA (TBAA metadata is
currently the prime example).
This means, for example, regardless of whether -fno-strict-aliasing was
provided, the vectorizer would only vectorize this loop with a runtime
memory-overlap check:
void foo(int *a, float *b) {
for (int i = 0; i < 1600; ++i)
a[i] = b[i];
}
This is suboptimal because the TBAA metadata already provides the information
necessary to show that this check unnecessary. Of course, the vectorizer has a
limit on the number of such checks it will insert, so in practice, ignoring
TBAA means not vectorizing more-complicated loops that we should.
This change causes the vectorizer to use an AliasSetTracker to keep track of
the pointers in the loop. The resulting alias sets are then used to partition
the space of dependency checks, and potential runtime checks; this results in
more-efficient vectorizations.
When pointer locations are added to the AliasSetTracker, two things are done:
1. The location size is set to UnknownSize (otherwise you'd not catch
inter-iteration dependencies)
2. For instructions in blocks that would need to be predicated, TBAA is
removed (because the metadata might have a control dependency on the condition
being speculated).
For non-predicated blocks, you can leave the TBAA metadata. This is safe
because you can't have an iteration dependency on the TBAA metadata (if you
did, and you unrolled sufficiently, you'd end up with the same pointer value
used by two accesses that TBAA says should not alias, and that would yield
undefined behavior).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213486 91177308-0d34-0410-b5e6-96231b3b80d8
75 lines
3.3 KiB
LLVM
75 lines
3.3 KiB
LLVM
; RUN: opt < %s -basicaa -loop-vectorize -force-vector-unroll=1 -force-vector-width=4 -dce -instcombine -S -enable-if-conversion | FileCheck %s
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target datalayout = "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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target triple = "x86_64-apple-macosx10.8.0"
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@A = global [36 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 24, i32 25, i32 26, i32 27, i32 28, i32 29, i32 30, i32 31, i32 32, i32 33, i32 34, i32 35], align 16
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@B = global [36 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 24, i32 25, i32 26, i32 27, i32 28, i32 29, i32 30, i32 31, i32 32, i32 33, i32 34, i32 35], align 16
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;CHECK-LABEL:@_Z5test1v(
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;CHECK: load <4 x i32>
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;CHECK: shufflevector <4 x i32>
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;CHECK: store <4 x i32>
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;CHECK: ret
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define i32 @_Z5test1v() nounwind uwtable ssp {
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br label %1
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; <label>:1 ; preds = %0, %1
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%p.02 = phi i32* [ getelementptr inbounds ([36 x i32]* @A, i64 0, i64 18), %0 ], [ %4, %1 ]
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%b.01 = phi i32* [ getelementptr inbounds ([36 x i32]* @B, i64 0, i64 0), %0 ], [ %5, %1 ]
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%2 = load i32* %b.01, align 4
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%3 = shl nsw i32 %2, 1
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store i32 %3, i32* %p.02, align 4
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%4 = getelementptr inbounds i32* %p.02, i64 -1
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%5 = getelementptr inbounds i32* %b.01, i64 1
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%6 = icmp eq i32* %4, getelementptr ([36 x i32]* @A, i64 128102389400760775, i64 3)
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br i1 %6, label %7, label %1
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; <label>:7 ; preds = %1
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ret i32 0
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}
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;CHECK-LABEL: @_Z5test2v(
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;CHECK: load <4 x i32>
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;CHECK: shufflevector <4 x i32>
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;CHECK: store <4 x i32>
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;CHECK: ret
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define i32 @_Z5test2v() nounwind uwtable ssp {
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br label %1
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; <label>:1 ; preds = %0, %1
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%p.02 = phi i32* [ getelementptr inbounds ([36 x i32]* @A, i64 0, i64 25), %0 ], [ %3, %1 ]
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%b.01 = phi i32* [ getelementptr inbounds ([36 x i32]* @B, i64 0, i64 2), %0 ], [ %4, %1 ]
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%2 = load i32* %b.01, align 4
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store i32 %2, i32* %p.02, align 4
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%3 = getelementptr inbounds i32* %p.02, i64 -1
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%4 = getelementptr inbounds i32* %b.01, i64 1
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%5 = icmp eq i32* %4, getelementptr inbounds ([36 x i32]* @A, i64 0, i64 18)
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br i1 %5, label %6, label %1
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; <label>:6 ; preds = %1
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ret i32 0
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}
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;CHECK:_Z5test3v
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;CHECK: load <4 x i32>
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;CHECK: shufflevector <4 x i32>
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;CHECK: store <4 x i32>
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;CHECK: ret
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define i32 @_Z5test3v() nounwind uwtable ssp {
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br label %1
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; <label>:1 ; preds = %0, %1
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%p.02 = phi i32* [ getelementptr inbounds ([36 x i32]* @A, i64 0, i64 29), %0 ], [ %3, %1 ]
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%b.01 = phi i32* [ getelementptr inbounds ([36 x i32]* @B, i64 0, i64 5), %0 ], [ %4, %1 ]
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%2 = load i32* %b.01, align 4
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store i32 %2, i32* %p.02, align 4
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%3 = getelementptr inbounds i32* %p.02, i64 -1
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%4 = getelementptr inbounds i32* %b.01, i64 1
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%5 = icmp eq i32* %3, getelementptr ([36 x i32]* @A, i64 128102389400760775, i64 3)
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br i1 %5, label %6, label %1
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; <label>:6 ; preds = %1
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ret i32 0
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}
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