From 181b5e81642163a54ebcbb37d91b0da06564260a Mon Sep 17 00:00:00 2001
From: Krzysztof Parzyszek <kparzysz@codeaurora.org>
Date: Fri, 30 Mar 2018 16:55:44 +0000
Subject: [PATCH] Revert "peel loops with runtime small trip counts"

This reverts commit r328854, it breaks some Hexagon tests.

llvm-svn: 328875
---
 .../Hexagon/HexagonTargetTransformInfo.cpp    |  8 ----
 lib/Transforms/Utils/LoopUnrollPeel.cpp       |  7 +---
 .../LoopUnroll/Hexagon/peel-small-loop.ll     | 37 -------------------
 3 files changed, 1 insertion(+), 51 deletions(-)
 delete mode 100644 test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll

diff --git a/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp b/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
index 51aab0b635a..3290b5931ad 100644
--- a/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
+++ b/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
@@ -44,14 +44,6 @@ HexagonTTIImpl::getPopcntSupport(unsigned IntTyWidthInBit) const {
 void HexagonTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
                                              TTI::UnrollingPreferences &UP) {
   UP.Runtime = UP.Partial = true;
-  // Only try to peel innermost loops with small runtime trip counts.
-  if (L && L->empty() &&
-      SE.getSmallConstantTripCount(L) == 0 &&
-      SE.getSmallConstantMaxTripCount(L) > 0 &&
-      SE.getSmallConstantMaxTripCount(L) <= 5) {
-    UP.PeelCount = 2;
-    UP.AllowPeeling = true;
-  }
 }
 
 bool HexagonTTIImpl::shouldFavorPostInc() const {
diff --git a/lib/Transforms/Utils/LoopUnrollPeel.cpp b/lib/Transforms/Utils/LoopUnrollPeel.cpp
index cfbecd59af3..5f465f328b0 100644
--- a/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ b/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -221,9 +221,6 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
                             TargetTransformInfo::UnrollingPreferences &UP,
                             unsigned &TripCount, ScalarEvolution &SE) {
   assert(LoopSize > 0 && "Zero loop size is not allowed!");
-  // Save the UP.PeelCount value set by the target in
-  // TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
-  unsigned TargetPeelCount = UP.PeelCount;
   UP.PeelCount = 0;
   if (!canPeel(L))
     return;
@@ -243,9 +240,7 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
     SmallDenseMap<PHINode *, unsigned> IterationsToInvariance;
     // Now go through all Phis to calculate their the number of iterations they
     // need to become invariants.
-    // Start the max computation with the UP.PeelCount value set by the target
-    // in TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
-    unsigned DesiredPeelCount = TargetPeelCount;
+    unsigned DesiredPeelCount = 0;
     BasicBlock *BackEdge = L->getLoopLatch();
     assert(BackEdge && "Loop is not in simplified form?");
     for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {
diff --git a/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll b/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
deleted file mode 100644
index 45c2553a70a..00000000000
--- a/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
+++ /dev/null
@@ -1,37 +0,0 @@
-; RUN: opt -loop-unroll -mtriple=hexagon -S < %s | FileCheck %s
-; Check that the loop is peeled twice for Hexagon.
-; CHECK: while.body.peel
-; CHECK: while.body.peel2
-
-%struct.STREAM = type { %union.anon, i32, i32 }
-%union.anon = type { i32* }
-
-define void @function(%struct.STREAM* nocapture readonly %b) local_unnamed_addr {
-entry:
-  %bitPtr3 = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 2
-  %0 = load i32, i32* %bitPtr3, align 4
-  %cmp11 = icmp ult i32 %0, 32
-  br i1 %cmp11, label %while.body.preheader, label %do.end
-
-while.body.preheader:
-  %value2 = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 1
-  %1 = load i32, i32* %value2, align 4
-  %w = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 0, i32 0
-  %2 = load i32*, i32** %w, align 4
-  br label %while.body
-
-while.body:
-  %bitPtr.014 = phi i32 [ %add, %while.body ], [ %0, %while.body.preheader ]
-  %value.013 = phi i32 [ %shl, %while.body ], [ %1, %while.body.preheader ]
-  %ptr.012 = phi i32* [ %incdec.ptr, %while.body ], [ %2, %while.body.preheader ]
-  %add = add nuw i32 %bitPtr.014, 8
-  %shr = lshr i32 %value.013, 24
-  %incdec.ptr = getelementptr inbounds i32, i32* %ptr.012, i32 1
-  store i32 %shr, i32* %ptr.012, align 4
-  %shl = shl i32 %value.013, 8
-  %cmp = icmp ult i32 %add, 17
-  br i1 %cmp, label %while.body, label %do.end
-
-do.end:
-  ret void
-}