From 0a6b8b7be0d6303b6574c2b2c098428c8b945736 Mon Sep 17 00:00:00 2001
From: Jingyue Wu <jingyue@google.com>
Date: Tue, 21 Jul 2015 21:50:39 +0000
Subject: [PATCH] [MDA] change BlockScanLimit into a command line option.

Summary:
In the benchmark (https://github.com/vetter/shoc) we are researching,
the duplicated load is not eliminated because MemoryDependenceAnalysis
hit the BlockScanLimit. This patch change it into a command line option
instead of a hardcoded value.

Patched by Xuetian Weng.

Test Plan: test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll

Reviewers: jingyue, reames

Subscribers: reames, llvm-commits

Differential Revision: http://reviews.llvm.org/D11366

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242842 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/MemoryDependenceAnalysis.cpp                 |  6 +++++-
 .../MemoryDependenceAnalysis/memdep-block-scan-limit.ll   | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll

diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 782a67bf72d..51e3c4d9d84 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -49,7 +49,11 @@ STATISTIC(NumCacheCompleteNonLocalPtr,
           "Number of block queries that were completely cached");
 
 // Limit for the number of instructions to scan in a block.
-static const unsigned int BlockScanLimit = 100;
+
+static cl::opt<unsigned> BlockScanLimit(
+    "memdep-block-scan-limit", cl::Hidden, cl::init(100),
+    cl::desc("The number of instructions to scan in a block in memory "
+             "dependency analysis (default = 100)"));
 
 // Limit on the number of memdep results to process.
 static const unsigned int NumResultsLimit = 100;
diff --git a/test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll b/test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll
new file mode 100644
index 00000000000..20ca31456fd
--- /dev/null
+++ b/test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll
@@ -0,0 +1,15 @@
+; RUN: opt -S -memdep -gvn -basicaa < %s | FileCheck %s
+; RUN: opt -S -memdep -memdep-block-scan-limit=1 -gvn -basicaa < %s | FileCheck %s --check-prefix=WITH-LIMIT
+; CHECK-LABEL: @test(
+; CHECK: load
+; CHECK-NOT: load
+; WITH-LIMIT-LABEL: @test(
+; WITH-LIMIT-CHECK: load
+; WITH-LIMIT-CHECK: load
+define i32 @test(i32* %p) {
+ %1 = load i32, i32* %p
+ %2 = add i32 %1, 3
+ %3 = load i32, i32* %p
+ %4 = add i32 %2, %3
+ ret i32 %4
+}
-- 
2.11.0