[IRCE] Avoid loop optimizations on pre and post loops

Summary:
This patch will add loop metadata on the pre and post loops generated by IRCE.
Currently, we have metadata for disabling optimizations such as vectorization,
unrolling, loop distribution and LICM versioning (and confirmed that these
optimizations check for the metadata before proceeding with the transformation).

The pre and post loops generated by IRCE need not go through loop opts (since
these are slow paths).

Added two test cases as well.

Reviewers: sanjoy, reames

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26806

llvm-svn: 289588

1 files changed, 81 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IRCE/add-metadata-pre-post-loops.ll b/llvm/test/Transforms/IRCE/add-metadata-pre-post-loops.ll
new file mode 100644
index 00000000000..488d4b479ba
--- /dev/null
+++ b/llvm/test/Transforms/IRCE/add-metadata-pre-post-loops.ll
@@ -0,0 +1,81 @@
+; RUN: opt -irce -S < %s 2>&1 | FileCheck %s
+
+; test that the pre and post loops have loop metadata which disables any further
+; loop optimizations.
+
+; generates a post loop, which should have metadata !llvm.loop !2
+; Function Attrs: alwaysinline
+define void @inner_loop(i32* %arr, i32* %a_len_ptr, i32 %n) #0 {
+; CHECK-LABEL: inner_loop(
+; CHECK-LABEL: in.bounds.postloop
+; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit.loopexit, !llvm.loop !2, !irce.loop.clone !7
+
+entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+loop:                                             ; preds = %in.bounds, %entry
+  %idx = phi i32 [ 0, %entry ], [ %idx.next, %in.bounds ]
+  %idx.next = add i32 %idx, 1
+  %abc = icmp slt i32 %idx, %len
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+in.bounds:                                        ; preds = %loop
+  %addr = getelementptr i32, i32* %arr, i32 %idx
+  store i32 0, i32* %addr
+  %next = icmp slt i32 %idx.next, %n
+  br i1 %next, label %loop, label %exit
+
+out.of.bounds:                                    ; preds = %loop
+  ret void
+
+exit:                                             ; preds = %in.bounds, %entry
+  ret void
+}
+
+; add loop metadata for pre and post loops
+define void @single_access_with_preloop(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32 %offset) {
+; CHECK-LABEL: @single_access_with_preloop(
+; CHECK-LABEL: in.bounds.preloop
+; CHECK: br i1 %14, label %loop.preloop, label %preloop.exit.selector, !llvm.loop !8, !irce.loop.clone !7
+; CHECK-LABEL: in.bounds.postloop
+; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit.loopexit, !llvm.loop !9, !irce.loop.clone !7
+ entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds ]
+  %idx.next = add i32 %idx, 1
+  %array.idx = add i32 %idx, %offset
+  %abc.high = icmp slt i32 %array.idx, %len
+  %abc.low = icmp sge i32 %array.idx, 0
+  %abc = and i1 %abc.low, %abc.high
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %addr = getelementptr i32, i32* %arr, i32 %array.idx
+  store i32 0, i32* %addr
+  %next = icmp slt i32 %idx.next, %n
+  br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+attributes #0 = { alwaysinline }
+
+!0 = !{i32 0, i32 2147483647}
+!1 = !{!"branch_weights", i32 64, i32 4}
+!2 = distinct !{!2, !3, !4, !5, !6}
+!3 = !{!"llvm.loop.unroll.disable"}
+!4 = !{!"llvm.loop.vectorize.enable", i1 false}
+!5 = !{!"llvm.loop.licm_versioning.disable"}
+!6 = !{!"llvm.loop.distribute.enable", i1 false}
+!7 = !{}
+!8 = distinct !{!8, !3, !4, !5}
+!9 = distinct !{!9, !3, !4, !5}