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llvm-project/llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll

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[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
; RUN: opt < %s -S -analyze -scalar-evolution | FileCheck %s
; Positive and negative tests for inferring flags like nsw from
; reasoning about how a poison value from overflow would trigger
; undefined behavior.
define void @foo() {
ret void
}
; Example where an add should get the nsw flag, so that a sext can be
; distributed over the add.
define void @test-add-nsw(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-nsw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nsw>
%index32 = add nsw i32 %i, %offset
; CHECK: %index64 =
; CHECK: --> {(sext i32 %offset to i64),+,1}<nsw>
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
call void @foo()
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where an add should get the nuw flag.
define void @test-add-nuw(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-nuw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nuw>
%index32 = add nuw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nuw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
[ValueTracking] ICmp instructions propagate poison This is a stripped down version of D19211, leaving out the questionable "branching in poison is UB" bit. llvm-svn: 271150
2016-05-29 08:31:18 +08:00
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
define void @test-add-nuw-from-icmp(float* %input, i32 %offset,
i32 %numIterations) {
; CHECK-LABEL: @test-add-nuw-from-icmp
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nuw>
%index32 = add nuw i32 %i, %offset
%cmp = icmp sgt i32 %index32, 0
%cmp.idx = sext i1 %cmp to i32
%ptr = getelementptr inbounds float, float* %input, i32 %cmp.idx
%nexti = add nuw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; With no load to trigger UB from poison, we cannot infer nsw.
define void @test-add-no-load(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-no-load
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nuw i32 %i, 1
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; The current code is only supposed to look at the loop header, so
; it should not infer nsw in this case, as that would require looking
; outside the loop header.
define void @test-add-not-header(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-not-header
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
br label %loop2
loop2:
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Same thing as test-add-not-header, but in this case only the load
; instruction is outside the loop header.
define void @test-add-not-header2(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-not-header2
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
Have isKnownNotFullPoison be smarter around control flow Summary: (... while still not using a PostDomTree) The way we use isKnownNotFullPoison from SCEV today, the new CFG walking logic will not trigger for any realistic cases -- it will kick in only for situations where we could have merged the contiguous basic blocks anyway[0], since the poison generating instruction dominates all of its non-PHI uses (which are the only uses we consider right now). However, having this change in place will allow a later bugfix to break fewer llvm-lit tests. [0]: i.e. cases where block A branches to block B and B is A's only successor and A is B's only predecessor. Reviewers: broune, bjarke.roune Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D19212 llvm-svn: 267175
2016-04-23 01:41:06 +08:00
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nsw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
br label %loop2
loop2:
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Similar to test-add-not-header, but in this case the load
; instruction may not be executed.
define void @test-add-not-header3(float* %input, i32 %offset, i32 %numIterations,
i1* %cond_buf) {
; CHECK-LABEL: @test-add-not-header3
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
Have isKnownNotFullPoison be smarter around control flow Summary: (... while still not using a PostDomTree) The way we use isKnownNotFullPoison from SCEV today, the new CFG walking logic will not trigger for any realistic cases -- it will kick in only for situations where we could have merged the contiguous basic blocks anyway[0], since the poison generating instruction dominates all of its non-PHI uses (which are the only uses we consider right now). However, having this change in place will allow a later bugfix to break fewer llvm-lit tests. [0]: i.e. cases where block A branches to block B and B is A's only successor and A is B's only predecessor. Reviewers: broune, bjarke.roune Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D19212 llvm-svn: 267175
2016-04-23 01:41:06 +08:00
%cond = load volatile i1, i1* %cond_buf
br i1 %cond, label %loop2, label %exit
loop2:
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Same thing as test-add-not-header2, except we have a few extra
; blocks.
define void @test-add-not-header4(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-not-header4
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nsw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
br label %loop3
loop3:
br label %loop4
loop4:
[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
br label %loop2
loop2:
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
Have isKnownNotFullPoison be smarter around control flow Summary: (... while still not using a PostDomTree) The way we use isKnownNotFullPoison from SCEV today, the new CFG walking logic will not trigger for any realistic cases -- it will kick in only for situations where we could have merged the contiguous basic blocks anyway[0], since the poison generating instruction dominates all of its non-PHI uses (which are the only uses we consider right now). However, having this change in place will allow a later bugfix to break fewer llvm-lit tests. [0]: i.e. cases where block A branches to block B and B is A's only successor and A is B's only predecessor. Reviewers: broune, bjarke.roune Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D19212 llvm-svn: 267175
2016-04-23 01:41:06 +08:00
; Demonstrate why we need a Visited set in llvm::isKnownNotFullPoison.
define void @test-add-not-header5(float* %input, i32 %offset) {
; CHECK-LABEL: @test-add-not-header5
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
br label %loop
exit:
ret void
}
[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
; The call instruction makes it not guaranteed that the add will be
; executed, since it could run forever or throw an exception, so we
; cannot assume that the UB is realized.
define void @test-add-call(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-call
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
call void @foo()
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Same issue as test-add-call, but this time the call is between the
; producer of poison and the load that consumes it.
define void @test-add-call2(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-call2
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
call void @foo()
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Without inbounds, GEP does not propagate poison in the very
; conservative approach used here.
define void @test-add-no-inbounds(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-no-inbounds
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Multiplication by a non-zero constant propagates poison if there is
; a nuw or nsw flag on the multiplication.
define void @test-add-mul-propagates(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-mul-propagates
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nsw>
%index32 = add nsw i32 %i, %offset
%indexmul = mul nuw i32 %index32, 2
%ptr = getelementptr inbounds float, float* %input, i32 %indexmul
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Multiplication by a non-constant should not propagate poison in the
; very conservative approach used here.
define void @test-add-mul-no-propagation(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-mul-no-propagation
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%indexmul = mul nsw i32 %index32, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %indexmul
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Multiplication by a non-zero constant does not propagate poison
; without a no-wrap flag.
define void @test-add-mul-no-propagation2(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-mul-no-propagation2
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nw>
%index32 = add nsw i32 %i, %offset
%indexmul = mul i32 %index32, 2
%ptr = getelementptr inbounds float, float* %input, i32 %indexmul
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Division by poison triggers UB.
define void @test-add-div(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-div
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %j =
; CHECK: --> {%offset,+,1}<nsw>
%j = add nsw i32 %i, %offset
%q = sdiv i32 %numIterations, %j
%nexti = add nsw i32 %i, 1
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Remainder of poison by non-poison divisor does not trigger UB.
define void @test-add-div2(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-div2
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %j =
; CHECK: --> {%offset,+,1}<nw>
%j = add nsw i32 %i, %offset
%q = sdiv i32 %j, %numIterations
%nexti = add nsw i32 %i, 1
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Store to poison address triggers UB.
define void @test-add-store(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-store
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {%offset,+,1}<nsw>
%index32 = add nsw i32 %i, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
store float 1.0, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Three sequential adds where the middle add should have nsw. There is
; a special case for sequential adds and this test covers that. We have to
; put the final add first in the program since otherwise the special case
; is not triggered, hence the strange basic block ordering.
define void @test-add-twice(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-add-twice
entry:
br label %loop
loop2:
; CHECK: %seq =
; CHECK: --> {(2 + %offset),+,1}<nw>
%seq = add nsw nuw i32 %index32, 1
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
%j = add nsw i32 %i, 1
; CHECK: %index32 =
[SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}" Summary: **Description** This makes `WidenIV::widenIVUse` (IndVarSimplify.cpp) fail to widen narrow IV uses in some cases. The latter affects IndVarSimplify which may not eliminate narrow IV's when there actually exists such a possibility, thereby producing ineffective code. When `WidenIV::widenIVUse` gets a NarrowUse such as `{(-2 + %inc.lcssa),+,1}<nsw><%for.body3>`, it first tries to get a wide recurrence for it via the `getWideRecurrence` call. `getWideRecurrence` returns recurrence like this: `{(sext i32 (-2 + %inc.lcssa) to i64),+,1}<nsw><%for.body3>`. Then a wide use operation is generated by `cloneIVUser`. The generated wide use is evaluated to `{(-2 + (sext i32 %inc.lcssa to i64))<nsw>,+,1}<nsw><%for.body3>`, which is different from the `getWideRecurrence` result. `cloneIVUser` sees the difference and returns nullptr. This patch also fixes the broken LLVM tests by adding missing <nsw> entries introduced by the correction. **Minimal reproducer:** ``` int foo(int a, int b, int c); int baz(); void bar() { int arr[20]; int i = 0; for (i = 0; i < 4; ++i) arr[i] = baz(); for (; i < 20; ++i) arr[i] = foo(arr[i - 4], arr[i - 3], arr[i - 2]); } ``` **Clang command line:** ``` clang++ -mllvm -debug -S -emit-llvm -O3 --target=aarch64-linux-elf test.cpp -o test.ir ``` **Expected result:** The ` -mllvm -debug` log shows that all the IV's for the second `for` loop have been eliminated. Reviewers: sanjoy Subscribers: atrick, asl, aemerson, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D20058 llvm-svn: 270695
2016-05-25 21:01:33 +08:00
; CHECK: --> {(1 + %offset)<nsw>,+,1}<nsw>
[SCEV] Apply NSW and NUW flags via poison value analysis Summary: Make Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs in some cases. This is based on reasoning about when poison from instructions with these flags would trigger undefined behavior. This gives a 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There does not seem to be clear agreement about when poison should be considered to propagate through instructions. In this analysis, poison propagates only in cases where that should be uncontroversial. This change makes LSR able to create induction variables for expressions like &ptr[i + offset] for loops like this: for (int i = 0; i < limit; ++i) { sum += ptr[i + offset]; } Here ptr is a 64 bit pointer and offset is a 32 bit integer. For NVPTX, LSR currently creates an induction variable for i + offset instead, which is not as fast. Improving this situation is what brings the 13% speed-up on some Eigen3-based Google-internal microbenchmarks for NVPTX. There are more details in this discussion on llvmdev. June: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-June/thread.html#87234 July: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-July/thread.html#87392 Patch by Bjarke Roune Reviewers: eliben, atrick, sanjoy Subscribers: majnemer, hfinkel, jingyue, meheff, llvm-commits Differential Revision: http://reviews.llvm.org/D11212 llvm-svn: 243460
2015-07-29 02:22:40 +08:00
%index32 = add nsw i32 %j, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
store float 1.0, float* %ptr, align 4
br label %loop2
exit:
ret void
}
[SCEV] Apply NSW and NUW flags via poison value analysis for sub, mul and shl Summary: http://reviews.llvm.org/D11212 made Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs for add instructions. This patch expands that to sub, mul and shl instructions. This change makes LSR able to generate pointer induction variables for loops like these, where the index is 32 bit and the pointer is 64 bit: for (int i = 0; i < numIterations; ++i) sum += ptr[i - offset]; for (int i = 0; i < numIterations; ++i) sum += ptr[i * stride]; for (int i = 0; i < numIterations; ++i) sum += ptr[3 * (i << 7)]; Reviewers: atrick, sanjoy Subscribers: sanjoy, majnemer, hfinkel, llvm-commits, meheff, jingyue, eliben Differential Revision: http://reviews.llvm.org/D11860 llvm-svn: 245118
2015-08-15 06:45:26 +08:00
; Example where a mul should get the nsw flag, so that a sext can be
; distributed over the mul.
define void @test-mul-nsw(float* %input, i32 %stride, i32 %numIterations) {
; CHECK-LABEL: @test-mul-nsw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {0,+,%stride}<nsw>
%index32 = mul nsw i32 %i, %stride
; CHECK: %index64 =
; CHECK: --> {0,+,(sext i32 %stride to i64)}<nsw>
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a mul should get the nuw flag.
define void @test-mul-nuw(float* %input, i32 %stride, i32 %numIterations) {
; CHECK-LABEL: @test-mul-nuw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {0,+,%stride}<nuw>
%index32 = mul nuw i32 %i, %stride
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nuw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a shl should get the nsw flag, so that a sext can be
; distributed over the shl.
define void @test-shl-nsw(float* %input, i32 %start, i32 %numIterations) {
; CHECK-LABEL: @test-shl-nsw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ %start, %entry ]
; CHECK: %index32 =
; CHECK: --> {(256 * %start),+,256}<nsw>
%index32 = shl nsw i32 %i, 8
; CHECK: %index64 =
; CHECK: --> {(sext i32 (256 * %start) to i64),+,256}<nsw>
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a shl should get the nuw flag.
define void @test-shl-nuw(float* %input, i32 %numIterations) {
; CHECK-LABEL: @test-shl-nuw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {0,+,512}<nuw>
%index32 = shl nuw i32 %i, 9
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nuw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a sub should *not* get the nsw flag, because of how
; scalar evolution represents A - B as A + (-B) and -B can wrap even
; in cases where A - B does not.
define void @test-sub-no-nsw(float* %input, i32 %start, i32 %sub, i32 %numIterations) {
; CHECK-LABEL: @test-sub-no-nsw
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ %start, %entry ]
; CHECK: %index32 =
; CHECK: --> {((-1 * %sub) + %start),+,1}<nw>
%index32 = sub nsw i32 %i, %sub
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a sub should get the nsw flag as the RHS cannot be the
; minimal signed value.
define void @test-sub-nsw(float* %input, i32 %start, i32 %sub, i32 %numIterations) {
; CHECK-LABEL: @test-sub-nsw
entry:
%halfsub = ashr i32 %sub, 1
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ %start, %entry ]
; CHECK: %index32 =
[SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}" Summary: **Description** This makes `WidenIV::widenIVUse` (IndVarSimplify.cpp) fail to widen narrow IV uses in some cases. The latter affects IndVarSimplify which may not eliminate narrow IV's when there actually exists such a possibility, thereby producing ineffective code. When `WidenIV::widenIVUse` gets a NarrowUse such as `{(-2 + %inc.lcssa),+,1}<nsw><%for.body3>`, it first tries to get a wide recurrence for it via the `getWideRecurrence` call. `getWideRecurrence` returns recurrence like this: `{(sext i32 (-2 + %inc.lcssa) to i64),+,1}<nsw><%for.body3>`. Then a wide use operation is generated by `cloneIVUser`. The generated wide use is evaluated to `{(-2 + (sext i32 %inc.lcssa to i64))<nsw>,+,1}<nsw><%for.body3>`, which is different from the `getWideRecurrence` result. `cloneIVUser` sees the difference and returns nullptr. This patch also fixes the broken LLVM tests by adding missing <nsw> entries introduced by the correction. **Minimal reproducer:** ``` int foo(int a, int b, int c); int baz(); void bar() { int arr[20]; int i = 0; for (i = 0; i < 4; ++i) arr[i] = baz(); for (; i < 20; ++i) arr[i] = foo(arr[i - 4], arr[i - 3], arr[i - 2]); } ``` **Clang command line:** ``` clang++ -mllvm -debug -S -emit-llvm -O3 --target=aarch64-linux-elf test.cpp -o test.ir ``` **Expected result:** The ` -mllvm -debug` log shows that all the IV's for the second `for` loop have been eliminated. Reviewers: sanjoy Subscribers: atrick, asl, aemerson, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D20058 llvm-svn: 270695
2016-05-25 21:01:33 +08:00
; CHECK: --> {((-1 * %halfsub)<nsw> + %start)<nsw>,+,1}<nsw>
[SCEV] Apply NSW and NUW flags via poison value analysis for sub, mul and shl Summary: http://reviews.llvm.org/D11212 made Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs for add instructions. This patch expands that to sub, mul and shl instructions. This change makes LSR able to generate pointer induction variables for loops like these, where the index is 32 bit and the pointer is 64 bit: for (int i = 0; i < numIterations; ++i) sum += ptr[i - offset]; for (int i = 0; i < numIterations; ++i) sum += ptr[i * stride]; for (int i = 0; i < numIterations; ++i) sum += ptr[3 * (i << 7)]; Reviewers: atrick, sanjoy Subscribers: sanjoy, majnemer, hfinkel, llvm-commits, meheff, jingyue, eliben Differential Revision: http://reviews.llvm.org/D11860 llvm-svn: 245118
2015-08-15 06:45:26 +08:00
%index32 = sub nsw i32 %i, %halfsub
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Example where a sub should get the nsw flag, since the LHS is non-negative,
; which implies that the RHS cannot be the minimal signed value.
define void @test-sub-nsw-lhs-non-negative(float* %input, i32 %sub, i32 %numIterations) {
; CHECK-LABEL: @test-sub-nsw-lhs-non-negative
entry:
br label %loop
loop:
%i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
; CHECK: %index32 =
; CHECK: --> {(-1 * %sub),+,1}<nsw>
%index32 = sub nsw i32 %i, %sub
; CHECK: %index64 =
; CHECK: --> {(sext i32 (-1 * %sub) to i64),+,1}<nsw>
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
%nexti = add nsw i32 %i, 1
%f = load float, float* %ptr, align 4
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
exit:
ret void
}
; Two adds with a sub in the middle and the sub should have nsw. There is
; a special case for sequential adds/subs and this test covers that. We have to
; put the final add first in the program since otherwise the special case
; is not triggered, hence the strange basic block ordering.
define void @test-sub-with-add(float* %input, i32 %offset, i32 %numIterations) {
; CHECK-LABEL: @test-sub-with-add
entry:
br label %loop
loop2:
; CHECK: %seq =
; CHECK: --> {(2 + (-1 * %offset)),+,1}<nw>
%seq = add nsw nuw i32 %index32, 1
%exitcond = icmp eq i32 %nexti, %numIterations
br i1 %exitcond, label %exit, label %loop
loop:
%i = phi i32 [ %nexti, %loop2 ], [ 0, %entry ]
%j = add nsw i32 %i, 1
; CHECK: %index32 =
[SCEV] No-wrap flags are not propagated when folding "{S,+,X}+T ==> {S+T,+,X}" Summary: **Description** This makes `WidenIV::widenIVUse` (IndVarSimplify.cpp) fail to widen narrow IV uses in some cases. The latter affects IndVarSimplify which may not eliminate narrow IV's when there actually exists such a possibility, thereby producing ineffective code. When `WidenIV::widenIVUse` gets a NarrowUse such as `{(-2 + %inc.lcssa),+,1}<nsw><%for.body3>`, it first tries to get a wide recurrence for it via the `getWideRecurrence` call. `getWideRecurrence` returns recurrence like this: `{(sext i32 (-2 + %inc.lcssa) to i64),+,1}<nsw><%for.body3>`. Then a wide use operation is generated by `cloneIVUser`. The generated wide use is evaluated to `{(-2 + (sext i32 %inc.lcssa to i64))<nsw>,+,1}<nsw><%for.body3>`, which is different from the `getWideRecurrence` result. `cloneIVUser` sees the difference and returns nullptr. This patch also fixes the broken LLVM tests by adding missing <nsw> entries introduced by the correction. **Minimal reproducer:** ``` int foo(int a, int b, int c); int baz(); void bar() { int arr[20]; int i = 0; for (i = 0; i < 4; ++i) arr[i] = baz(); for (; i < 20; ++i) arr[i] = foo(arr[i - 4], arr[i - 3], arr[i - 2]); } ``` **Clang command line:** ``` clang++ -mllvm -debug -S -emit-llvm -O3 --target=aarch64-linux-elf test.cpp -o test.ir ``` **Expected result:** The ` -mllvm -debug` log shows that all the IV's for the second `for` loop have been eliminated. Reviewers: sanjoy Subscribers: atrick, asl, aemerson, mzolotukhin, llvm-commits Differential Revision: http://reviews.llvm.org/D20058 llvm-svn: 270695
2016-05-25 21:01:33 +08:00
; CHECK: --> {(1 + (-1 * %offset))<nsw>,+,1}<nsw>
[SCEV] Apply NSW and NUW flags via poison value analysis for sub, mul and shl Summary: http://reviews.llvm.org/D11212 made Scalar Evolution able to propagate NSW and NUW flags from instructions to SCEVs for add instructions. This patch expands that to sub, mul and shl instructions. This change makes LSR able to generate pointer induction variables for loops like these, where the index is 32 bit and the pointer is 64 bit: for (int i = 0; i < numIterations; ++i) sum += ptr[i - offset]; for (int i = 0; i < numIterations; ++i) sum += ptr[i * stride]; for (int i = 0; i < numIterations; ++i) sum += ptr[3 * (i << 7)]; Reviewers: atrick, sanjoy Subscribers: sanjoy, majnemer, hfinkel, llvm-commits, meheff, jingyue, eliben Differential Revision: http://reviews.llvm.org/D11860 llvm-svn: 245118
2015-08-15 06:45:26 +08:00
%index32 = sub nsw i32 %j, %offset
%ptr = getelementptr inbounds float, float* %input, i32 %index32
%nexti = add nsw i32 %i, 1
store float 1.0, float* %ptr, align 4
br label %loop2
exit:
ret void
}
; Subtraction of two recurrences. The addition in the SCEV that this
; maps to is NSW, but the negation of the RHS does not since that
; recurrence could be the most negative representable value.
define void @subrecurrences(i32 %outer_l, i32 %inner_l, i32 %val) {
; CHECK-LABEL: @subrecurrences
entry:
br label %outer
outer:
%o_idx = phi i32 [ 0, %entry ], [ %o_idx.inc, %outer.be ]
%o_idx.inc = add nsw i32 %o_idx, 1
%cond = icmp eq i32 %o_idx, %val
br i1 %cond, label %inner, label %outer.be
inner:
%i_idx = phi i32 [ 0, %outer ], [ %i_idx.inc, %inner ]
%i_idx.inc = add nsw i32 %i_idx, 1
; CHECK: %v =
; CHECK-NEXT: --> {{[{][{]}}-1,+,-1}<nw><%outer>,+,1}<nsw><%inner>
%v = sub nsw i32 %i_idx, %o_idx.inc
%forub = udiv i32 1, %v
%cond2 = icmp eq i32 %i_idx, %inner_l
br i1 %cond2, label %outer.be, label %inner
outer.be:
%cond3 = icmp eq i32 %o_idx, %outer_l
br i1 %cond3, label %exit, label %outer
exit:
ret void
}
SCEV: Don't assert about non-SCEV-able value in isSCEVExprNeverPoison() (PR28932) Differential Revision: https://reviews.llvm.org/D23594 llvm-svn: 278999
2016-08-18 06:50:18 +08:00
; PR28932: Don't assert on non-SCEV-able value %2.
%struct.anon = type { i8* }
@a = common global %struct.anon* null, align 8
@b = common global i32 0, align 4
declare { i32, i1 } @llvm.ssub.with.overflow.i32(i32, i32)
declare void @llvm.trap()
define i32 @pr28932() {
entry:
%.pre = load %struct.anon*, %struct.anon** @a, align 8
%.pre7 = load i32, i32* @b, align 4
br label %for.cond
for.cond: ; preds = %cont6, %entry
%0 = phi i32 [ %3, %cont6 ], [ %.pre7, %entry ]
%1 = phi %struct.anon* [ %.ph, %cont6 ], [ %.pre, %entry ]
%tobool = icmp eq %struct.anon* %1, null
%2 = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %0, i32 1)
%3 = extractvalue { i32, i1 } %2, 0
%4 = extractvalue { i32, i1 } %2, 1
%idxprom = sext i32 %3 to i64
%5 = getelementptr inbounds %struct.anon, %struct.anon* %1, i64 0, i32 0
%6 = load i8*, i8** %5, align 8
%7 = getelementptr inbounds i8, i8* %6, i64 %idxprom
%8 = load i8, i8* %7, align 1
br i1 %tobool, label %if.else, label %if.then
if.then: ; preds = %for.cond
br i1 %4, label %trap, label %cont6
trap: ; preds = %if.else, %if.then
tail call void @llvm.trap()
unreachable
if.else: ; preds = %for.cond
br i1 %4, label %trap, label %cont1
cont1: ; preds = %if.else
%conv5 = sext i8 %8 to i64
%9 = inttoptr i64 %conv5 to %struct.anon*
store %struct.anon* %9, %struct.anon** @a, align 8
br label %cont6
cont6: ; preds = %cont1, %if.then
%.ph = phi %struct.anon* [ %9, %cont1 ], [ %1, %if.then ]
store i32 %3, i32* @b, align 4
br label %for.cond
}