[llvm] r297122 - [LoopUnrolling] Fix loop size check for peeling
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 6 22:03:15 PST 2017
Author: sanjoy
Date: Tue Mar 7 00:03:15 2017
New Revision: 297122
URL: http://llvm.org/viewvc/llvm-project?rev=297122&view=rev
Log:
[LoopUnrolling] Fix loop size check for peeling
Summary:
We should check if loop size allows us to peel at least one iteration
before we do so.
Patch by Max Kazantsev!
Reviewers: sanjoy, mkuper, efriedma
Reviewed By: mkuper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30632
Modified:
llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
llvm/trunk/test/Transforms/LoopUnroll/peel-loop-not-forced.ll
Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp?rev=297122&r1=297121&r2=297122&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp Tue Mar 7 00:03:15 2017
@@ -75,7 +75,9 @@ void llvm::computePeelCount(Loop *L, uns
// its only back edge. If there is such Phi, peeling 1 iteration from the
// loop is profitable, because starting from 2nd iteration we will have an
// invariant instead of this Phi.
- if (auto *BackEdge = L->getLoopLatch()) {
+ if (LoopSize <= UP.Threshold) {
+ BasicBlock *BackEdge = L->getLoopLatch();
+ assert(BackEdge && "Loop is not in simplified form?");
BasicBlock *Header = L->getHeader();
// Iterate over Phis to find one with invariant input on back edge.
bool FoundCandidate = false;
Modified: llvm/trunk/test/Transforms/LoopUnroll/peel-loop-not-forced.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/peel-loop-not-forced.ll?rev=297122&r1=297121&r2=297122&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/peel-loop-not-forced.ll (original)
+++ llvm/trunk/test/Transforms/LoopUnroll/peel-loop-not-forced.ll Tue Mar 7 00:03:15 2017
@@ -1,4 +1,4 @@
-; RUN: opt < %s -S -loop-unroll | FileCheck %s
+; RUN: opt < %s -S -loop-unroll -unroll-threshold=4 | FileCheck %s
define i32 @invariant_backedge_1(i32 %a, i32 %b) {
; CHECK-LABEL: @invariant_backedge_1
@@ -18,6 +18,34 @@ loop:
%incsum = add i32 %sum, %plus
%inc = add i32 %i, 1
%cmp = icmp slt i32 %i, 1000
+
+ br i1 %cmp, label %loop, label %exit
+
+exit:
+ ret i32 %sum
+}
+
+; Peeling should fail due to method size.
+define i32 @invariant_backedge_2(i32 %a, i32 %b) {
+; CHECK-LABEL: @invariant_backedge_2
+; CHECK-NOT: loop.peel:
+; CHECK: loop:
+; CHECK: %i = phi
+; CHECK: %sum = phi
+; CHECK: %plus = phi
+entry:
+ br label %loop
+
+loop:
+ %i = phi i32 [ 0, %entry ], [ %inc, %loop ]
+ %sum = phi i32 [ 0, %entry ], [ %incsum2, %loop ]
+ %plus = phi i32 [ %a, %entry ], [ %b, %loop ]
+
+ %incsum = add i32 %sum, %plus
+ %incsum2 = add i32 %incsum, %plus
+ %inc = add i32 %i, 1
+ %cmp = icmp slt i32 %i, 1000
+
br i1 %cmp, label %loop, label %exit
exit:
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