Reimplement heuristic for estimating complete-unroll optimization effects.

Summary:
This patch reimplements heuristic that tries to estimate optimization beneftis
from complete loop unrolling.

In this patch I kept the minimal changes - e.g. I removed code handling
branches and folding compares. That's a promising area, but now there
are too many questions to discuss before we can enable it.

Test Plan: Tests are included in the patch.

Reviewers: hfinkel, chandlerc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8816

llvm-svn: 237156

2 files changed, 36 insertions, 2 deletions

diff --git a/llvm/test/Transforms/LoopUnroll/full-unroll-bad-geps.ll b/llvm/test/Transforms/LoopUnroll/full-unroll-bad-geps.ll
new file mode 100644
index 00000000000..4c99bc73880
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/full-unroll-bad-geps.ll
@@ -0,0 +1,34 @@
+; Check that we don't crash on corner cases.
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=10  -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 -o /dev/null
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @foo1() {
+entry:
+  br label %for.body
+
+for.body:
+  %phi = phi i64 [ 0, %entry ], [ %inc, %for.body ]
+  %idx = zext i32 undef to i64
+  %add.ptr = getelementptr inbounds i64, i64* null, i64 %idx
+  %inc = add nuw nsw i64 %phi, 1
+  %cmp = icmp ult i64 %inc, 999
+  br i1 %cmp, label %for.body, label %for.exit
+
+for.exit:
+  ret void
+}
+
+define void @foo2() {
+entry:
+  br label %for.body
+
+for.body:
+  %phi = phi i64 [ 0, %entry ], [ %inc, %for.body ]
+  %x = getelementptr i32, <4 x i32*> undef, <4 x i32> <i32 1, i32 1, i32 1, i32 1>
+  %inc = add nuw nsw i64 %phi, 1
+  %cmp = icmp ult i64 %inc, 999
+  br i1 %cmp, label %for.body, label %for.exit
+
+for.exit:
+  ret void
+}
diff --git a/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll b/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll
index a9104adeb97..2dab2fbf2e4 100644
--- a/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll
+++ b/llvm/test/Transforms/LoopUnroll/full-unroll-heuristics.ll
@@ -17,8 +17,8 @@
 ; 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-max-iteration-count-to-analyze=1000 -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-max-iteration-count-to-analyze=1000 -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-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=10  -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 | FileCheck %s -check-prefix=TEST1
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=100 -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 | FileCheck %s -check-prefix=TEST2
 ; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -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-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=100 -unroll-threshold=100 -unroll-percent-of-optimized-for-complete-unroll=80 | FileCheck %s -check-prefix=TEST4