bf6e1c26cf
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
150 lines
5.4 KiB
LLVM
150 lines
5.4 KiB
LLVM
; REQUIRES: asserts
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; RUN: opt < %s -basicaa -loop-interchange -verify-dom-info -S -debug 2>&1 | FileCheck %s
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;; We test profitability model in these test cases.
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@A = common global [100 x [100 x i32]] zeroinitializer
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@B = common global [100 x [100 x i32]] zeroinitializer
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;;---------------------------------------Test case 01---------------------------------
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;; Loops interchange will result in code vectorization and hence profitable. Check for interchange.
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;; for(int i=1;i<N;i++)
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;; for(int j=1;j<N;j++)
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;; A[j][i] = A[j - 1][i] + B[j][i];
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; CHECK: Not interchanging loops. Cannot prove legality.
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define void @interchange_01(i32 %N) {
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entry:
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%cmp27 = icmp sgt i32 %N, 1
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br i1 %cmp27, label %for.cond1.preheader.lr.ph, label %for.end16
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for.cond1.preheader.lr.ph:
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%0 = add i32 %N, -1
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br label %for.body3.preheader
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for.body3.preheader:
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%indvars.iv30 = phi i64 [ 1, %for.cond1.preheader.lr.ph ], [ %indvars.iv.next31, %for.inc14 ]
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br label %for.body3
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for.body3:
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%indvars.iv = phi i64 [ %indvars.iv.next, %for.body3 ], [ 1, %for.body3.preheader ]
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%1 = add nsw i64 %indvars.iv, -1
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%arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %1, i64 %indvars.iv30
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%2 = load i32, i32* %arrayidx5
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%arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @B, i64 0, i64 %indvars.iv, i64 %indvars.iv30
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%3 = load i32, i32* %arrayidx9
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%add = add nsw i32 %3, %2
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%arrayidx13 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv30
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store i32 %add, i32* %arrayidx13
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %0
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br i1 %exitcond, label %for.inc14, label %for.body3
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for.inc14:
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%indvars.iv.next31 = add nuw nsw i64 %indvars.iv30, 1
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%lftr.wideiv32 = trunc i64 %indvars.iv30 to i32
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%exitcond33 = icmp eq i32 %lftr.wideiv32, %0
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br i1 %exitcond33, label %for.end16, label %for.body3.preheader
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for.end16:
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ret void
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}
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;; ---------------------------------------Test case 02---------------------------------
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;; Check loop interchange profitability model.
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;; This tests profitability model when operands of getelementpointer and not exactly the induction variable but some
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;; arithmetic operation on them.
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;; for(int i=1;i<N;i++)
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;; for(int j=1;j<N;j++)
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;; A[j-1][i-1] = A[j - 1][i-1] + B[j-1][i-1];
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; CHECK: Not interchanging loops. Cannot prove legality.
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define void @interchange_02(i32 %N) {
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entry:
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%cmp32 = icmp sgt i32 %N, 1
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br i1 %cmp32, label %for.cond1.preheader.lr.ph, label %for.end21
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for.cond1.preheader.lr.ph:
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%0 = add i32 %N, -1
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br label %for.body3.lr.ph
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for.body3.lr.ph:
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%indvars.iv35 = phi i64 [ 1, %for.cond1.preheader.lr.ph ], [ %indvars.iv.next36, %for.inc19 ]
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%1 = add nsw i64 %indvars.iv35, -1
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br label %for.body3
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for.body3:
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%indvars.iv = phi i64 [ 1, %for.body3.lr.ph ], [ %indvars.iv.next, %for.body3 ]
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%2 = add nsw i64 %indvars.iv, -1
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%arrayidx6 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %2, i64 %1
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%3 = load i32, i32* %arrayidx6
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%arrayidx12 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @B, i64 0, i64 %2, i64 %1
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%4 = load i32, i32* %arrayidx12
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%add = add nsw i32 %4, %3
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store i32 %add, i32* %arrayidx6
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %0
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br i1 %exitcond, label %for.inc19, label %for.body3
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for.inc19:
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%indvars.iv.next36 = add nuw nsw i64 %indvars.iv35, 1
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%lftr.wideiv38 = trunc i64 %indvars.iv35 to i32
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%exitcond39 = icmp eq i32 %lftr.wideiv38, %0
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br i1 %exitcond39, label %for.end21, label %for.body3.lr.ph
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for.end21:
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ret void
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}
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;;---------------------------------------Test case 03---------------------------------
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;; Loops interchange is not profitable.
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;; for(int i=1;i<N;i++)
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;; for(int j=1;j<N;j++)
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;; A[i-1][j-1] = A[i - 1][j-1] + B[i][j];
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; CHECK: Not interchanging loops. Cannot prove legality.
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define void @interchange_03(i32 %N){
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entry:
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%cmp31 = icmp sgt i32 %N, 1
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br i1 %cmp31, label %for.cond1.preheader.lr.ph, label %for.end19
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for.cond1.preheader.lr.ph:
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%0 = add i32 %N, -1
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br label %for.body3.lr.ph
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for.body3.lr.ph:
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%indvars.iv34 = phi i64 [ 1, %for.cond1.preheader.lr.ph ], [ %indvars.iv.next35, %for.inc17 ]
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%1 = add nsw i64 %indvars.iv34, -1
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br label %for.body3
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for.body3:
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%indvars.iv = phi i64 [ 1, %for.body3.lr.ph ], [ %indvars.iv.next, %for.body3 ]
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%2 = add nsw i64 %indvars.iv, -1
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%arrayidx6 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %1, i64 %2
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%3 = load i32, i32* %arrayidx6
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%arrayidx10 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @B, i64 0, i64 %indvars.iv34, i64 %indvars.iv
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%4 = load i32, i32* %arrayidx10
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%add = add nsw i32 %4, %3
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store i32 %add, i32* %arrayidx6
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %0
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br i1 %exitcond, label %for.inc17, label %for.body3
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for.inc17:
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%indvars.iv.next35 = add nuw nsw i64 %indvars.iv34, 1
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%lftr.wideiv37 = trunc i64 %indvars.iv34 to i32
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%exitcond38 = icmp eq i32 %lftr.wideiv37, %0
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br i1 %exitcond38, label %for.end19, label %for.body3.lr.ph
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for.end19:
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ret void
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}
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