[LoopUnrollRuntime] Avoid high-cost trip count computation.
Summary:
Runtime unrolling of loops needs to emit an expression to compute the
loop's runtime trip-count. Avoid runtime unrolling if this computation
will be expensive.
Depends on D8993.
Reviewers: atrick
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8994
llvm-svn: 234846
diff --git a/llvm/test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll b/llvm/test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll
new file mode 100644
index 0000000..6b1943f
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/high-cost-trip-count-computation.ll
@@ -0,0 +1,27 @@
+; RUN: opt -S -unroll-runtime -loop-unroll < %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+;; Check that we don't emit expensive instructions to compute trip
+;; counts when unrolling loops.
+
+define i32 @test(i64 %v12, i8* %array, i64* %loc) {
+; CHECK-LABEL: @test(
+; CHECK-NOT: udiv
+entry:
+ %step = load i64, i64* %loc, !range !0
+ br label %loop
+
+loop: ; preds = %entry, %loop
+ %k.015 = phi i64 [ %v15, %loop ], [ %v12, %entry ]
+ %v14 = getelementptr inbounds i8, i8* %array, i64 %k.015
+ store i8 0, i8* %v14
+ %v15 = add nuw nsw i64 %k.015, %step
+ %v16 = icmp slt i64 %v15, 8193
+ br i1 %v16, label %loop, label %loopexit
+
+loopexit: ; preds = %loop
+ ret i32 0
+}
+
+!0 = !{i64 1, i64 100}