[llvm] r309547 - [LoopInterchange] Do not interchange loops with function calls.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 31 02:00:52 PDT 2017
Author: fhahn
Date: Mon Jul 31 02:00:52 2017
New Revision: 309547
URL: http://llvm.org/viewvc/llvm-project?rev=309547&view=rev
Log:
[LoopInterchange] Do not interchange loops with function calls.
Summary:
Without any information about the called function, we cannot be sure
that it is safe to interchange loops which contain function calls. For
example there could be dependences that prevent interchanging between
accesses in the called function and the loops. Even functions without any
parameters could cause problems, as they could access memory using
global pointers.
For now, I think it is only safe to interchange loops with calls marked
as readnone.
With this patch, the LLVM test suite passes with `-O3 -mllvm
-enable-loopinterchange` and LoopInterchangeProfitability::isProfitable
returning true for all loops. check-llvm and check-clang also pass when
bootstrapped in a similar fashion, although only 3 loops got
interchanged.
Reviewers: karthikthecool, blitz.opensource, hfinkel, mcrosier, mkuper
Reviewed By: mcrosier
Subscribers: mzolotukhin, llvm-commits
Differential Revision: https://reviews.llvm.org/D35489
Added:
llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
llvm/trunk/test/Transforms/LoopInterchange/interchange-flow-dep-outer.ll
llvm/trunk/test/Transforms/LoopInterchange/not-interchanged-tightly-nested.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp?rev=309547&r1=309546&r2=309547&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp Mon Jul 31 02:00:52 2017
@@ -958,6 +958,18 @@ bool LoopInterchangeLegality::canInterch
return false;
}
+ // Check if outer and inner loop contain legal instructions only.
+ for (auto *BB : OuterLoop->blocks())
+ for (Instruction &I : *BB)
+ if (CallInst *CI = dyn_cast<CallInst>(&I)) {
+ // readnone functions do not prevent interchanging.
+ if (CI->doesNotReadMemory())
+ continue;
+ DEBUG(dbgs() << "Loops with call instructions cannot be interchanged "
+ << "safely.");
+ return false;
+ }
+
// Create unique Preheaders if we already do not have one.
BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
Added: llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll?rev=309547&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll (added)
+++ llvm/trunk/test/Transforms/LoopInterchange/call-instructions.ll Mon Jul 31 02:00:52 2017
@@ -0,0 +1,158 @@
+; RUN: opt < %s -basicaa -loop-interchange -S | FileCheck %s
+;; We test the complete .ll for adjustment in outer loop header/latch and inner loop header/latch.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at A = common global [100 x [100 x i32]] zeroinitializer
+
+declare void @foo(i64 %a)
+declare void @bar(i64 %a) readnone
+
+;;--------------------------------------Test case 01------------------------------------
+;; Not safe to interchange, because the called function `foo` is not marked as
+;; readnone, so it could introduce dependences.
+;;
+;; for(int i=0;i<N;i++) {
+;; for(int j=1;j<N;j++) {
+;; foo(i);
+;; A[j][i] = A[j][i]+k;
+;; }
+;; }
+
+define void @interchange_01(i32 %k, i32 %N) {
+entry:
+ %cmp21 = icmp sgt i32 %N, 0
+ br i1 %cmp21, label %for1.ph, label %exit
+
+for1.ph:
+ %cmp219 = icmp sgt i32 %N, 1
+ %0 = add i32 %N, -1
+ br label %for1.header
+
+for1.header:
+ %indvars.iv23 = phi i64 [ 0, %for1.ph ], [ %indvars.iv.next24, %for1.inc10 ]
+ br i1 %cmp219, label %for2.ph, label %for1.inc10
+
+for2.ph:
+ br label %for2
+
+for2:
+ %indvars.iv = phi i64 [ %indvars.iv.next, %for2 ], [ 1, %for2.ph ]
+ call void @foo(i64 %indvars.iv23)
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv23
+ %1 = load i32, i32* %arrayidx5
+ %add = add nsw i32 %1, %k
+ store i32 %add, i32* %arrayidx5
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %lftr.wideiv = trunc i64 %indvars.iv to i32
+ %exitcond = icmp eq i32 %lftr.wideiv, %0
+ br i1 %exitcond, label %for2.loopexit , label %for2
+
+for2.loopexit:
+ br label %for1.inc10
+
+for1.inc10:
+ %indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
+ %lftr.wideiv25 = trunc i64 %indvars.iv23 to i32
+ %exitcond26 = icmp eq i32 %lftr.wideiv25, %0
+ br i1 %exitcond26, label %for1.loopexit, label %for1.header
+
+for1.loopexit:
+ br label %exit
+
+exit:
+ ret void
+}
+
+; CHECK-LABEL: @interchange_01
+; CHECK: for1.ph:
+; CHECK: br label %for1.header
+
+; CHECK: for1.header:
+; CHECK-NEXT: %indvars.iv23 = phi i64 [ 0, %for1.ph ], [ %indvars.iv.next24, %for1.inc10 ]
+; CHECK-NEXT: br i1 %cmp219, label %for2.ph, label %for1.inc10
+
+; CHECK: for2:
+; CHECK: br i1 %exitcond, label %for2.loopexit, label %for2
+
+; CHECK: for1.inc10:
+; CHECK: br i1 %exitcond26, label %for1.loopexit, label %for1.header
+
+; CHECK: for1.loopexit:
+; CHECK-NEXT: br label %exit
+
+
+;;--------------------------------------Test case 02------------------------------------
+;; Safe to interchange, because the called function `bar` is marked as readnone,
+;; so it cannot introduce dependences.
+;;
+;; for(int i=0;i<N;i++) {
+;; for(int j=1;j<N;j++) {
+;; bar(i);
+;; A[j][i] = A[j][i]+k;
+;; }
+;; }
+
+define void @interchange_02(i32 %k, i32 %N) {
+entry:
+ %cmp21 = icmp sgt i32 %N, 0
+ br i1 %cmp21, label %for1.ph, label %exit
+
+for1.ph:
+ %cmp219 = icmp sgt i32 %N, 1
+ %0 = add i32 %N, -1
+ br label %for1.header
+
+for1.header:
+ %indvars.iv23 = phi i64 [ 0, %for1.ph ], [ %indvars.iv.next24, %for1.inc10 ]
+ br i1 %cmp219, label %for2.ph, label %for1.inc10
+
+for2.ph:
+ br label %for2
+
+for2:
+ %indvars.iv = phi i64 [ %indvars.iv.next, %for2 ], [ 1, %for2.ph ]
+ call void @bar(i64 %indvars.iv23)
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv23
+ %1 = load i32, i32* %arrayidx5
+ %add = add nsw i32 %1, %k
+ store i32 %add, i32* %arrayidx5
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %lftr.wideiv = trunc i64 %indvars.iv to i32
+ %exitcond = icmp eq i32 %lftr.wideiv, %0
+ br i1 %exitcond, label %for2.loopexit , label %for2
+
+for2.loopexit:
+ br label %for1.inc10
+
+for1.inc10:
+ %indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
+ %lftr.wideiv25 = trunc i64 %indvars.iv23 to i32
+ %exitcond26 = icmp eq i32 %lftr.wideiv25, %0
+ br i1 %exitcond26, label %for1.loopexit, label %for1.header
+
+for1.loopexit:
+ br label %exit
+
+exit:
+ ret void
+}
+
+; CHECK-LABEL: @interchange_02
+; CHECK: for1.header:
+; CHECK-NEXT: %indvars.iv23 = phi i64 [ 0, %for1.ph ], [ %indvars.iv.next24, %for1.inc10 ]
+; CHECK-NEXT: br i1 %cmp219, label %for2.split1, label %for1.loopexit
+
+; CHECK: for2.split1:
+; CHECK: br label %for2.loopexit
+
+; CHECK: for2.split:
+; CHECK-NEXT: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK: br i1 %exitcond, label %for1.loopexit, label %for2
+
+; CHECK: for2.loopexit:
+; CHECK-NEXT: br label %for1.inc10
+
+; CHECK: for1.inc10:
+; CHECK: br i1 %exitcond26, label %for2.split, label %for1.header
Modified: llvm/trunk/test/Transforms/LoopInterchange/interchange-flow-dep-outer.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/interchange-flow-dep-outer.ll?rev=309547&r1=309546&r2=309547&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/interchange-flow-dep-outer.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/interchange-flow-dep-outer.ll Mon Jul 31 02:00:52 2017
@@ -65,8 +65,8 @@ for.body9:
br i1 %exitcond, label %for.body9, label %for.cond.cleanup8
}
-declare double @fn1()
-declare void @fn2(double)
+declare double @fn1() readnone
+declare void @fn2(double) readnone
;; After interchange %indvars.iv (j) should increment as the middle loop.
Modified: llvm/trunk/test/Transforms/LoopInterchange/not-interchanged-tightly-nested.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/not-interchanged-tightly-nested.ll?rev=309547&r1=309546&r2=309547&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/not-interchanged-tightly-nested.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/not-interchanged-tightly-nested.ll Mon Jul 31 02:00:52 2017
@@ -93,7 +93,7 @@ for.end17:
; CHECK: ret void
-declare void @foo(...)
+declare void @foo(...) readnone
;; Loops not tightly nested are not interchanged
;; for(int j=0;j<N;j++) {
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