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[MDA] change BlockScanLimit into a command line option.

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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
This commit is contained in:
Jingyue Wu 2015-07-21 21:50:39 +00:00
parent a14dff356b
commit 0a6b8b7be0
2 changed files with 20 additions and 1 deletions
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6
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -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;

15
test/Analysis/MemoryDependenceAnalysis/memdep-block-scan-limit.ll Normal file
View File

@ -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
}