[llvm] r330738 - [LoopInterchange] Make isProfitableForVectorization slightly more conservative.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 24 09:55:32 PDT 2018
Author: fhahn
Date: Tue Apr 24 09:55:32 2018
New Revision: 330738
URL: http://llvm.org/viewvc/llvm-project?rev=330738&view=rev
Log:
[LoopInterchange] Make isProfitableForVectorization slightly more conservative.
After D43236, we started interchanging loops with empty dependence
matrices. In isProfitableForVectorization, we try to determine if
interchanging makes the loop dependences more friendly to the
vectorizer. If there are no dependences, we should not interchange,
based on that heuristic.
Reviewers: efriedma, mcrosier, karthikthecool, blitz.opensource
Reviewed By: mcrosier
Differential Revision: https://reviews.llvm.org/D45208
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
llvm/trunk/test/Transforms/LoopInterchange/interchange-no-deps.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp?rev=330738&r1=330737&r2=330738&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp Tue Apr 24 09:55:32 2018
@@ -1112,7 +1112,8 @@ static bool isProfitableForVectorization
}
// If outer loop has dependence and inner loop is loop independent then it is
// profitable to interchange to enable parallelism.
- return true;
+ // If there are no dependences, interchanging will not improve anything.
+ return !DepMatrix.empty();
}
bool LoopInterchangeProfitability::isProfitable(unsigned InnerLoopId,
Modified: llvm/trunk/test/Transforms/LoopInterchange/interchange-no-deps.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/interchange-no-deps.ll?rev=330738&r1=330737&r2=330738&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/interchange-no-deps.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/interchange-no-deps.ll Tue Apr 24 09:55:32 2018
@@ -1,31 +1,94 @@
-; RUN: opt < %s -loop-interchange -verify-dom-info -verify-loop-info -S \
-; RUN: -pass-remarks=loop-interchange 2>&1 | FileCheck %s
-; CHECK: Loop interchanged with enclosing loop.
+; RUN: opt < %s -loop-interchange -simplifycfg -pass-remarks-output=%t \
+; RUN: -pass-remarks=loop-interchange -pass-remarks-missed=loop-interchange -stats -S 2>&1 \
+; RUN: | FileCheck -check-prefix=STATS %s
+; RUN: FileCheck -input-file %t %s
-; no_deps_interchange just access a single nested array and can be interchange.
-define i32 @no_deps_interchange([1024 x i32]* nocapture %Arr, i32 %k) local_unnamed_addr #0 {
+; no_deps_interchange just accesses a single nested array and can be interchange.
+; CHECK: Name: Interchanged
+; CHECK-NEXT: Function: no_deps_interchange
+define i32 @no_deps_interchange([1024 x i32]* nocapture %Arr) local_unnamed_addr #0 {
entry:
- br label %for.body
+ br label %for1.header
-for.body: ; preds = %entry, %for.cond.cleanup3
- %indvars.iv19 = phi i64 [ 0, %entry ], [ %indvars.iv.next20, %for.cond.cleanup3 ]
- br label %for.body4
+for1.header: ; preds = %entry, %for1.inc
+ %indvars.iv19 = phi i64 [ 0, %entry ], [ %indvars.iv.next20, %for1.inc ]
+ br label %for2
-for.body4: ; preds = %for.body, %for.body4
- %indvars.iv = phi i64 [ 0, %for.body ], [ %indvars.iv.next, %for.body4 ]
+for2: ; preds = %for1.header, %for2
+ %indvars.iv = phi i64 [ 0, %for1.header ], [ %indvars.iv.next, %for2 ]
%arrayidx6 = getelementptr inbounds [1024 x i32], [1024 x i32]* %Arr, i64 %indvars.iv, i64 %indvars.iv19
store i32 0, i32* %arrayidx6, align 4
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp ne i64 %indvars.iv.next, 1024
- br i1 %exitcond, label %for.body4, label %for.cond.cleanup3
+ br i1 %exitcond, label %for2, label %for1.inc
-for.cond.cleanup3: ; preds = %for.body4
+for1.inc:
%indvars.iv.next20 = add nuw nsw i64 %indvars.iv19, 1
%exitcond21 = icmp ne i64 %indvars.iv.next20, 1024
- br i1 %exitcond21, label %for.body, label %for.cond.cleanup
+ br i1 %exitcond21, label %for1.header, label %exit
+exit: ; preds = %for1.inc
+ ret i32 0
+
+}
-for.cond.cleanup: ; preds = %for.cond.cleanup3
+; Only the inner loop induction variable is used for memory accesses.
+; Interchanging is not beneficial.
+; CHECK: Name: InterchangeNotProfitable
+; CHECK-NEXT: Function: no_bad_order
+define i32 @no_bad_order(i32* %Arr) {
+entry:
+ br label %for1.header
+
+for1.header: ; preds = %entry, %for1.inc
+ %indvars.iv19 = phi i64 [ 0, %entry ], [ %indvars.iv.next20, %for1.inc ]
+ br label %for2
+
+for2: ; preds = %for1.header, %for2
+ %indvars.iv = phi i64 [ 0, %for1.header ], [ %indvars.iv.next, %for2 ]
+ %arrayidx6 = getelementptr inbounds i32, i32* %Arr, i64 %indvars.iv
+ store i32 0, i32* %arrayidx6, align 4
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp ne i64 %indvars.iv.next, 1024
+ br i1 %exitcond, label %for2, label %for1.inc
+
+for1.inc:
+ %indvars.iv.next20 = add nuw nsw i64 %indvars.iv19, 1
+ %exitcond21 = icmp ne i64 %indvars.iv.next20, 1024
+ br i1 %exitcond21, label %for1.header, label %exit
+
+exit: ; preds = %for1.inc
ret i32 0
}
+
+; No memory access using any induction variables, interchanging not beneficial.
+; CHECK: Name: InterchangeNotProfitable
+; CHECK-NEXT: Function: no_mem_instrs
+define i32 @no_mem_instrs(i64* %ptr) {
+entry:
+ br label %for1.header
+
+for1.header: ; preds = %entry, %for1.inc
+ %indvars.iv19 = phi i64 [ 0, %entry ], [ %indvars.iv.next20, %for1.inc ]
+ br label %for2
+
+for2: ; preds = %for1.header, %for2
+ %indvars.iv = phi i64 [ 0, %for1.header ], [ %indvars.iv.next, %for2 ]
+ store i64 %indvars.iv, i64* %ptr, align 4
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp ne i64 %indvars.iv.next, 1024
+ br i1 %exitcond, label %for2, label %for1.inc
+
+for1.inc:
+ %indvars.iv.next20 = add nuw nsw i64 %indvars.iv19, 1
+ %exitcond21 = icmp ne i64 %indvars.iv.next20, 1024
+ br i1 %exitcond21, label %for1.header, label %exit
+
+exit: ; preds = %for1.inc
+ ret i32 0
+}
+
+
+; Check stats, we interchanged 1 out of 3 loops.
+; STATS: 1 loop-interchange - Number of loops interchanged
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