[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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; RUN: llc < %s -asm-verbose=false -fast-isel=false -disable-wasm-fallthrough-return-opt | FileCheck %s
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2018-07-02 18:03:49 +02:00
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target triple = "wasm32-unknown-unknown"
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[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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2018-06-29 23:27:20 +02:00
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; This should be treated as a non-splat vector of pow2 divisor, so sdivs will be
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; transformed to shrs in DAGCombiner. There will be 4 stores and 3 shrs (For '1'
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; entry we don't need a shr).
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[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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; CHECK-LABEL: vector_sdiv:
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; CHECK-DAG: i32.store
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2018-06-27 21:35:50 +02:00
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; CHECK-DAG: i32.shr_u
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[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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; CHECK-DAG: i32.store
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2018-06-27 21:35:50 +02:00
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; CHECK-DAG: i32.shr_u
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[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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; CHECK-DAG: i32.store
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2018-06-27 21:35:50 +02:00
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; CHECK-DAG: i32.shr_u
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[DAGCombiner] Fix a case of 1 in non-splat vector pow2 divisor
Summary:
D42479 (rL329525) enabled SDIV combine for pow2 non-splat vector
dividers. But when there is a 1 in a vector, the instruction sequence to
be generated involves shifting a value by the number of its bit widths,
which is undefined
(https://github.com/llvm-mirror/llvm/blob/c64f4dbfe31e509f9c1092b951e524b056245af8/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L6000-L6006).
Especially, in architectures that do not support vector instructions,
each of element in a vector will be computed separately using scalar
operations, and then the resulting value will be undef for '1' values
in a vector.
(All 1's vector is fine; only vectors mixed with 1 and others will be
affected.)
Reviewers: RKSimon, jgravelle-google
Subscribers: jfb, dschuff, sbc100, jgravelle-google, llvm-commits
Differential Revision: https://reviews.llvm.org/D46161
llvm-svn: 331092
2018-04-28 00:23:11 +02:00
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; CHECK-DAG: i32.store
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define void @vector_sdiv(<4 x i32>* %x, <4 x i32>* readonly %y) {
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entry:
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%0 = load <4 x i32>, <4 x i32>* %y, align 16
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%div = sdiv <4 x i32> %0, <i32 1, i32 4, i32 2, i32 8>
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store <4 x i32> %div, <4 x i32>* %x, align 16
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ret void
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}
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