From 783633e29e0a24cfbb9a3d5bbf401b2bcbb212d7 Mon Sep 17 00:00:00 2001
From: Daniil Fukalov <daniil.fukalov@amd.com>
Date: Thu, 26 Jan 2017 13:33:17 +0000
Subject: [PATCH] [SCEV] Introduce add operation inlining limit

Inlining in getAddExpr() can cause abnormal computational time in some cases.
New parameter -scev-addops-inline-threshold is intruduced with default value 500.

Reviewers: sanjoy

Subscribers: mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D28812

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293176 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ScalarEvolution.cpp                |  8 ++++++++
 .../ScalarEvolution/max-addops-inline.ll        | 17 +++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 test/Analysis/ScalarEvolution/max-addops-inline.ll

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 18fcb0e85b6..ee09c8f3c01 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -127,6 +127,11 @@ static cl::opt<unsigned> MulOpsInlineThreshold(
     cl::desc("Threshold for inlining multiplication operands into a SCEV"),
     cl::init(1000));
 
+static cl::opt<unsigned> AddOpsInlineThreshold(
+    "scev-addops-inline-threshold", cl::Hidden,
+    cl::desc("Threshold for inlining multiplication operands into a SCEV"),
+    cl::init(500));
+
 static cl::opt<unsigned>
     MaxCompareDepth("scalar-evolution-max-compare-depth", cl::Hidden,
                     cl::desc("Maximum depth of recursive compare complexity"),
@@ -2219,6 +2224,9 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
   if (Idx < Ops.size()) {
     bool DeletedAdd = false;
     while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
+      if (Ops.size() > AddOpsInlineThreshold ||
+          Add->getNumOperands() > AddOpsInlineThreshold)
+        break;
       // If we have an add, expand the add operands onto the end of the operands
       // list.
       Ops.erase(Ops.begin()+Idx);
diff --git a/test/Analysis/ScalarEvolution/max-addops-inline.ll b/test/Analysis/ScalarEvolution/max-addops-inline.ll
new file mode 100644
index 00000000000..2701ed32839
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/max-addops-inline.ll
@@ -0,0 +1,17 @@
+; RUN: opt -analyze -scalar-evolution -scev-addops-inline-threshold=1 < %s | FileCheck --check-prefix=CHECK1 %s
+; RUN: opt -analyze -scalar-evolution -scev-addops-inline-threshold=10 < %s | FileCheck --check-prefix=CHECK10 %s
+
+define i32 @foo(i64 %p0, i32 %p1) {
+; CHECK1: %add2 = add nsw i32 %mul1, %add
+; CHECK1-NEXT: -->  ((trunc i64 %p0 to i32) * (1 + (trunc i64 %p0 to i32)) * (1 + %p1))
+
+; CHECK10: %add2 = add nsw i32 %mul1, %add
+; CHECK10-NEXT: -->  ((trunc i64 %p0 to i32) * (1 + ((trunc i64 %p0 to i32) * (1 + %p1)) + %p1))
+entry:
+  %tr = trunc i64 %p0 to i32
+  %mul = mul nsw i32 %tr, %p1
+  %add = add nsw i32 %mul, %tr
+  %mul1 = mul nsw i32 %add, %tr
+  %add2 = add nsw i32 %mul1, %add
+  ret i32 %add2
+}
-- 
2.40.0