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clang-p2996/llvm/test/Transforms/LoopInterchange/reductions.ll
Sebastian Pop bf6e1c26cf DA: remove uses of GEP, only ask SCEV 
It's been quite some time the Dependence Analysis (DA) is broken,
as it uses the GEP representation to "identify" multi-dimensional arrays.
It even wrongly detects multi-dimensional arrays in single nested loops:

from test/Analysis/DependenceAnalysis/Coupled.ll, example @couple6
;; for (long int i = 0; i < 50; i++) {
;; A[i][3*i - 6] = i;
;; *B++ = A[i][i];

DA used to detect two subscripts, which makes no sense in the LLVM IR
or in C/C++ semantics, as there are no guarantees as in Fortran of
subscripts not overlapping into a next array dimension:

maximum nesting levels = 1
SrcPtrSCEV = %A
DstPtrSCEV = %A
using GEPs
subscript 0
    src = {0,+,1}<nuw><nsw><%for.body>
    dst = {0,+,1}<nuw><nsw><%for.body>
    class = 1
    loops = {1}
subscript 1
    src = {-6,+,3}<nsw><%for.body>
    dst = {0,+,1}<nuw><nsw><%for.body>
    class = 1
    loops = {1}
Separable = {}
Coupled = {1}

With the current patch, DA will correctly work on only one dimension:

maximum nesting levels = 1
SrcSCEV = {(-2424 + %A)<nsw>,+,1212}<%for.body>
DstSCEV = {%A,+,404}<%for.body>
subscript 0
    src = {(-2424 + %A)<nsw>,+,1212}<%for.body>
    dst = {%A,+,404}<%for.body>
    class = 1
    loops = {1}
Separable = {0}
Coupled = {}

This change removes all uses of GEP from DA, and we now only rely
on the SCEV representation.

The patch does not turn on -da-delinearize by default, and so the DA analysis
will be more conservative in the case of multi-dimensional memory accesses in
nested loops.

I disabled some interchange tests, as the DA is not able to disambiguate
the dependence anymore. To make DA stronger, we may need to
compute a bound on the number of iterations based on the access functions
and array dimensions.

The patch cleans up all the CHECKs in test/Transforms/LoopInterchange/*.ll to
avoid checking for snippets of LLVM IR: this form of checking is very hard to
maintain. Instead, we now check for output of the pass that are more meaningful
than dozens of lines of LLVM IR. Some tests now require -debug messages and thus
only enabled with asserts.

Patch written by Sebastian Pop and Aditya Kumar.

Differential Revision: https://reviews.llvm.org/D35430

llvm-svn: 326837
2018-03-06 21:55:59 +00:00

223 lines
9.7 KiB
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; REQUIRES: asserts
; RUN: opt < %s -basicaa -loop-interchange -verify-dom-info -S -debug 2>&1 | FileCheck %s
@A = common global [500 x [500 x i32]] zeroinitializer
@X = common global i32 0
@B = common global [500 x [500 x i32]] zeroinitializer
@Y = common global i32 0
;; for( int i=1;i<N;i++)
;; for( int j=1;j<N;j++)
;; X+=A[j][i];
;; Loop is interchanged check that the phi nodes are split and the promoted value is used instead of the reduction phi.
; CHECK: Loops interchanged.
define void @reduction_01(i32 %N) {
entry:
%cmp16 = icmp sgt i32 %N, 1
br i1 %cmp16, label %for.body3.lr.ph, label %for.end8
for.body3.lr.ph: ; preds = %entry, %for.cond1.for.inc6_crit_edge
%indvars.iv18 = phi i64 [ %indvars.iv.next19, %for.cond1.for.inc6_crit_edge ], [ 1, %entry ]
%X.promoted = load i32, i32* @X
br label %for.body3
for.body3: ; preds = %for.body3, %for.body3.lr.ph
%indvars.iv = phi i64 [ 1, %for.body3.lr.ph ], [ %indvars.iv.next, %for.body3 ]
%add15 = phi i32 [ %X.promoted, %for.body3.lr.ph ], [ %add, %for.body3 ]
%arrayidx5 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv18
%0 = load i32, i32* %arrayidx5
%add = add nsw i32 %add15, %0
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %N
br i1 %exitcond, label %for.cond1.for.inc6_crit_edge, label %for.body3
for.cond1.for.inc6_crit_edge: ; preds = %for.body3
store i32 %add, i32* @X
%indvars.iv.next19 = add nuw nsw i64 %indvars.iv18, 1
%lftr.wideiv20 = trunc i64 %indvars.iv.next19 to i32
%exitcond21 = icmp eq i32 %lftr.wideiv20, %N
br i1 %exitcond21, label %for.end8, label %for.body3.lr.ph
for.end8: ; preds = %for.cond1.for.inc6_crit_edge, %entry
ret void
}
;; Test for more than 1 reductions inside a loop.
;; for( int i=1;i<N;i++)
;; for( int j=1;j<N;j++)
;; for( int k=1;k<N;k++) {
;; X+=A[k][j];
;; Y+=B[k][i];
;; }
;; Loop is interchanged check that the phi nodes are split and the promoted value is used instead of the reduction phi.
; CHECK: Loops interchanged.
define void @reduction_02(i32 %N) {
entry:
%cmp34 = icmp sgt i32 %N, 1
br i1 %cmp34, label %for.cond4.preheader.preheader, label %for.end19
for.cond4.preheader.preheader: ; preds = %entry, %for.inc17
%indvars.iv40 = phi i64 [ %indvars.iv.next41, %for.inc17 ], [ 1, %entry ]
br label %for.body6.lr.ph
for.body6.lr.ph: ; preds = %for.cond4.for.inc14_crit_edge, %for.cond4.preheader.preheader
%indvars.iv36 = phi i64 [ %indvars.iv.next37, %for.cond4.for.inc14_crit_edge ], [ 1, %for.cond4.preheader.preheader ]
%X.promoted = load i32, i32* @X
%Y.promoted = load i32, i32* @Y
br label %for.body6
for.body6: ; preds = %for.body6, %for.body6.lr.ph
%indvars.iv = phi i64 [ 1, %for.body6.lr.ph ], [ %indvars.iv.next, %for.body6 ]
%add1331 = phi i32 [ %Y.promoted, %for.body6.lr.ph ], [ %add13, %for.body6 ]
%add30 = phi i32 [ %X.promoted, %for.body6.lr.ph ], [ %add, %for.body6 ]
%arrayidx8 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv36
%0 = load i32, i32* %arrayidx8
%add = add nsw i32 %add30, %0
%arrayidx12 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @B, i64 0, i64 %indvars.iv, i64 %indvars.iv40
%1 = load i32, i32* %arrayidx12
%add13 = add nsw i32 %add1331, %1
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %N
br i1 %exitcond, label %for.cond4.for.inc14_crit_edge, label %for.body6
for.cond4.for.inc14_crit_edge: ; preds = %for.body6
store i32 %add, i32* @X
store i32 %add13, i32* @Y
%indvars.iv.next37 = add nuw nsw i64 %indvars.iv36, 1
%lftr.wideiv38 = trunc i64 %indvars.iv.next37 to i32
%exitcond39 = icmp eq i32 %lftr.wideiv38, %N
br i1 %exitcond39, label %for.inc17, label %for.body6.lr.ph
for.inc17: ; preds = %for.cond4.for.inc14_crit_edge
%indvars.iv.next41 = add nuw nsw i64 %indvars.iv40, 1
%lftr.wideiv42 = trunc i64 %indvars.iv.next41 to i32
%exitcond43 = icmp eq i32 %lftr.wideiv42, %N
br i1 %exitcond43, label %for.end19, label %for.cond4.preheader.preheader
for.end19: ; preds = %for.inc17, %entry
ret void
}
;; Not tightly nested. Do not interchange.
;; for( int i=1;i<N;i++)
;; for( int j=1;j<N;j++) {
;; for( int k=1;k<N;k++) {
;; X+=A[k][j];
;; }
;; Y+=B[j][i];
;; }
;; Not tightly nested. Do not interchange.
;; Not interchanged hence the phi's in the inner loop will not be split. Check for the same.
; CHECK: Not interchanging loops. Cannot prove legality.
define void @reduction_03(i32 %N) {
entry:
%cmp35 = icmp sgt i32 %N, 1
br i1 %cmp35, label %for.cond4.preheader.lr.ph, label %for.end19
for.cond4.preheader.lr.ph: ; preds = %entry, %for.cond1.for.inc17_crit_edge
%indvars.iv41 = phi i64 [ %indvars.iv.next42, %for.cond1.for.inc17_crit_edge ], [ 1, %entry ]
%Y.promoted = load i32, i32* @Y
br label %for.body6.lr.ph
for.body6.lr.ph: ; preds = %for.cond4.preheader.lr.ph, %for.cond4.for.end_crit_edge
%indvars.iv37 = phi i64 [ 1, %for.cond4.preheader.lr.ph ], [ %indvars.iv.next38, %for.cond4.for.end_crit_edge ]
%add1334 = phi i32 [ %Y.promoted, %for.cond4.preheader.lr.ph ], [ %add13, %for.cond4.for.end_crit_edge ]
%X.promoted = load i32, i32* @X
br label %for.body6
for.body6: ; preds = %for.body6, %for.body6.lr.ph
%indvars.iv = phi i64 [ 1, %for.body6.lr.ph ], [ %indvars.iv.next, %for.body6 ]
%add31 = phi i32 [ %X.promoted, %for.body6.lr.ph ], [ %add, %for.body6 ]
%arrayidx8 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv37
%0 = load i32, i32* %arrayidx8
%add = add nsw i32 %add31, %0
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %N
br i1 %exitcond, label %for.cond4.for.end_crit_edge, label %for.body6
for.cond4.for.end_crit_edge: ; preds = %for.body6
store i32 %add, i32* @X
%arrayidx12 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @B, i64 0, i64 %indvars.iv37, i64 %indvars.iv41
%1 = load i32, i32* %arrayidx12
%add13 = add nsw i32 %add1334, %1
%indvars.iv.next38 = add nuw nsw i64 %indvars.iv37, 1
%lftr.wideiv39 = trunc i64 %indvars.iv.next38 to i32
%exitcond40 = icmp eq i32 %lftr.wideiv39, %N
br i1 %exitcond40, label %for.cond1.for.inc17_crit_edge, label %for.body6.lr.ph
for.cond1.for.inc17_crit_edge: ; preds = %for.cond4.for.end_crit_edge
store i32 %add13, i32* @Y
%indvars.iv.next42 = add nuw nsw i64 %indvars.iv41, 1
%lftr.wideiv43 = trunc i64 %indvars.iv.next42 to i32
%exitcond44 = icmp eq i32 %lftr.wideiv43, %N
br i1 %exitcond44, label %for.end19, label %for.cond4.preheader.lr.ph
for.end19: ; preds = %for.cond1.for.inc17_crit_edge, %entry
ret void
}
;; Multiple use of reduction not safe. Do not interchange.
;; for( int i=1;i<N;i++)
;; for( int j=1;j<N;j++)
;; for( int k=1;k<N;k++) {
;; X+=A[k][j];
;; Y+=X;
;; }
;; Not interchanged hence the phi's in the inner loop will not be split. Check for the same.
; CHECK: Not interchanging loops. Cannot prove legality.
define void @reduction_04(i32 %N) {
entry:
%cmp28 = icmp sgt i32 %N, 1
br i1 %cmp28, label %for.cond4.preheader.preheader, label %for.end15
for.cond4.preheader.preheader: ; preds = %entry, %for.inc13
%i.029 = phi i32 [ %inc14, %for.inc13 ], [ 1, %entry ]
br label %for.body6.lr.ph
for.body6.lr.ph: ; preds = %for.cond4.for.inc10_crit_edge, %for.cond4.preheader.preheader
%indvars.iv30 = phi i64 [ %indvars.iv.next31, %for.cond4.for.inc10_crit_edge ], [ 1, %for.cond4.preheader.preheader ]
%X.promoted = load i32, i32* @X
%Y.promoted = load i32, i32* @Y
br label %for.body6
for.body6: ; preds = %for.body6, %for.body6.lr.ph
%indvars.iv = phi i64 [ 1, %for.body6.lr.ph ], [ %indvars.iv.next, %for.body6 ]
%add925 = phi i32 [ %Y.promoted, %for.body6.lr.ph ], [ %add9, %for.body6 ]
%add24 = phi i32 [ %X.promoted, %for.body6.lr.ph ], [ %add, %for.body6 ]
%arrayidx8 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv30
%0 = load i32, i32* %arrayidx8
%add = add nsw i32 %add24, %0
%add9 = add nsw i32 %add925, %add
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %N
br i1 %exitcond, label %for.cond4.for.inc10_crit_edge, label %for.body6
for.cond4.for.inc10_crit_edge: ; preds = %for.body6
store i32 %add, i32* @X
store i32 %add9, i32* @Y
%indvars.iv.next31 = add nuw nsw i64 %indvars.iv30, 1
%lftr.wideiv32 = trunc i64 %indvars.iv.next31 to i32
%exitcond33 = icmp eq i32 %lftr.wideiv32, %N
br i1 %exitcond33, label %for.inc13, label %for.body6.lr.ph
for.inc13: ; preds = %for.cond4.for.inc10_crit_edge
%inc14 = add nuw nsw i32 %i.029, 1
%exitcond34 = icmp eq i32 %inc14, %N
br i1 %exitcond34, label %for.end15, label %for.cond4.preheader.preheader
for.end15: ; preds = %for.inc13, %entry
ret void
}
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