From 990cd4c2e27368583c7f4f684f91e9523014e3d3 Mon Sep 17 00:00:00 2001
From: Johannes Doerfert <doerfert@cs.uni-saarland.de>
Date: Fri, 3 Oct 2014 19:11:10 +0000
Subject: [PATCH] Add option to limit the maximal number of parallel threads.

Differential Revision: http://reviews.llvm.org/D5581

llvm-svn: 219004
---
 polly/lib/CodeGen/LoopGenerators.cpp          |  8 ++++-
 .../test/Isl/CodeGen/openmp_limit_threads.ll  | 36 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 polly/test/Isl/CodeGen/openmp_limit_threads.ll

diff --git a/polly/lib/CodeGen/LoopGenerators.cpp b/polly/lib/CodeGen/LoopGenerators.cpp
index 491d088080ce..10595f903418 100644
--- a/polly/lib/CodeGen/LoopGenerators.cpp
+++ b/polly/lib/CodeGen/LoopGenerators.cpp
@@ -18,10 +18,16 @@
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Support/CommandLine.h"
 
 using namespace llvm;
 using namespace polly;
 
+static cl::opt<int>
+    PollyNumThreads("polly-num-threads",
+                    cl::desc("Number of threads to use (0 = auto)"), cl::Hidden,
+                    cl::init(0));
+
 // We generate a loop of either of the following structures:
 //
 //              BeforeBB                      BeforeBB
@@ -185,7 +191,7 @@ void ParallelLoopGenerator::createCallSpawnThreads(Value *SubFn,
     F = Function::Create(Ty, Linkage, Name, M);
   }
 
-  Value *NumberOfThreads = ConstantInt::get(LongType, 0);
+  Value *NumberOfThreads = ConstantInt::get(LongType, PollyNumThreads);
   Value *Args[] = {SubFn, SubFnParam, NumberOfThreads, LB, UB, Stride};
 
   Builder.CreateCall(F, Args);
diff --git a/polly/test/Isl/CodeGen/openmp_limit_threads.ll b/polly/test/Isl/CodeGen/openmp_limit_threads.ll
new file mode 100644
index 000000000000..3d304580af7c
--- /dev/null
+++ b/polly/test/Isl/CodeGen/openmp_limit_threads.ll
@@ -0,0 +1,36 @@
+; RUN: opt %loadPolly -polly-codegen -enable-polly-openmp -S < %s | FileCheck %s --check-prefix=AUTO
+; RUN: opt %loadPolly -polly-codegen -enable-polly-openmp -polly-num-threads=1 -S < %s | FileCheck %s --check-prefix=ONE
+; RUN: opt %loadPolly -polly-codegen -enable-polly-openmp -polly-num-threads=4 -S < %s | FileCheck %s --check-prefix=FOUR
+;
+; AUTO: call void @GOMP_parallel_loop_runtime_start(void (i8*)* @jd.polly.subfn, i8* %polly.par.userContext{{[0-9]*}}, i64 0, i64 0, i64 1024, i64 1)
+; ONE: call void @GOMP_parallel_loop_runtime_start(void (i8*)* @jd.polly.subfn, i8* %polly.par.userContext{{[0-9]*}}, i64 1, i64 0, i64 1024, i64 1)
+; FOUR: call void @GOMP_parallel_loop_runtime_start(void (i8*)* @jd.polly.subfn, i8* %polly.par.userContext{{[0-9]*}}, i64 4, i64 0, i64 1024, i64 1)
+;
+;    void jd(int *A) {
+;      for (int i = 0; i < 1024; i++)
+;        A[i] = 0;
+;    }
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @jd(i32* %A) {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %exitcond = icmp ne i64 %indvars.iv, 1024
+  br i1 %exitcond, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %arrayidx = getelementptr inbounds i32* %A, i64 %indvars.iv
+  store i32 0, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}