peel loops with runtime small trip counts

For Hexagon, peeling loops with small runtime trip count is beneficial for our
benchmarks. We set PeelCount in HexagonTargetInfo.cpp and we use PeelCount set
by the target for computing the desired peel count.

Differential Revision: https://reviews.llvm.org/D44880

llvm-svn: 329042

1 files changed, 37 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll b/llvm/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
new file mode 100644
index 00000000000..45c2553a70a
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
@@ -0,0 +1,37 @@
+; 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
+}