Add a test case for new unrolling heuristics.

THe heuristics were added in r228265 and r228434.

llvm-svn: 228713

1 files changed, 59 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll b/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll
new file mode 100644
index 00000000000..7f0f0b2d2e0
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll
@@ -0,0 +1,59 @@
+; In this test we check how heuristics for complete unrolling work. We have
+; three knobs:
+;  1) -unroll-threshold
+;  2) -unroll-absolute-threshold and
+;  3) -unroll-percent-of-optimized-for-complete-unroll
+;
+; They control loop-unrolling according to the following rules:
+;  * If size of unrolled loop exceeds the absoulte threshold, we don't unroll
+;    this loop under any circumstances.
+;  * If size of unrolled loop is below the '-unroll-threshold', then we'll
+;    consider this loop as a very small one, and completely unroll it.
+;  * If a loop size is between these two tresholds, we only do complete unroll
+;    it if estimated number of potentially optimized instructions is high (we
+;    specify the minimal percent of such instructions).
+
+; In this particular test-case, complete unrolling will allow later
+; optimizations to remove ~55% of the instructions, the loop body size is 9,
+; and unrolled size is 65.
+
+; RUN: opt < %s -S -loop-unroll -unroll-absolute-threshold=10  -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=30 | FileCheck %s -check-prefix=TEST1
+; RUN: opt < %s -S -loop-unroll -unroll-absolute-threshold=100 -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=30 | FileCheck %s -check-prefix=TEST2
+; RUN: opt < %s -S -loop-unroll -unroll-absolute-threshold=100 -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=80 | FileCheck %s -check-prefix=TEST3
+; RUN: opt < %s -S -loop-unroll -unroll-absolute-threshold=100 -unroll-threshold=100 -unroll-percent-of-optimized-for-complete-unroll=80 | FileCheck %s -check-prefix=TEST4
+
+; If the absolute threshold is too low, or if we can't optimize away requested
+; percent of instructions, we shouldn't unroll:
+; TEST1: %array_const_idx = getelementptr inbounds [9 x i32]* @known_constant, i64 0, i64 %iv
+; TEST3: %array_const_idx = getelementptr inbounds [9 x i32]* @known_constant, i64 0, i64 %iv
+
+; Otherwise, we should:
+; TEST2-NOT: %array_const_idx = getelementptr inbounds [9 x i32]* @known_constant, i64 0, i64 %iv
+
+; Also, we should unroll if the 'unroll-threshold' is big enough:
+; TEST4-NOT: %array_const_idx = getelementptr inbounds [9 x i32]* @known_constant, i64 0, i64 %iv
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+@known_constant = internal unnamed_addr constant [9 x i32] [i32 0, i32 -1, i32 0, i32 -1, i32 5, i32 -1, i32 0, i32 -1, i32 0], align 16
+
+define i32 @foo(i32* noalias nocapture readonly %src) {
+entry:
+  br label %loop
+
+loop:                                                ; preds = %loop, %entry
+  %iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
+  %r  = phi i32 [ 0, %entry ], [ %add, %loop ]
+  %arrayidx = getelementptr inbounds i32* %src, i64 %iv
+  %src_element = load i32* %arrayidx, align 4
+  %array_const_idx = getelementptr inbounds [9 x i32]* @known_constant, i64 0, i64 %iv
+  %const_array_element = load i32* %array_const_idx, align 4
+  %mul = mul nsw i32 %src_element, %const_array_element
+  %add = add nsw i32 %mul, %r
+  %inc = add nuw nsw i64 %iv, 1
+  %exitcond86.i = icmp eq i64 %inc, 9
+  br i1 %exitcond86.i, label %loop.end, label %loop
+
+loop.end:                                            ; preds = %loop
+  %r.lcssa = phi i32 [ %r, %loop ]
+  ret i32 %r.lcssa
+}