[llvm-cov] Multi-threaded implementation of prepareFileReports method.

Summary:
Local testing has demonstrated a great speed improvement, compare the following:

1) Existing version:
```
$ time llvm-cov show -format=html -output-dir=report -instr-profile=... ...
The tool has been launched:                            00:00:00
Loading coverage data:                                 00:00:00
Get unique source files:                               00:00:33
Creating an index out of the source files:             00:00:34
Going into prepareFileReports:                         00:00:34
Going to emit summary information for each file:       00:28:55 <-- 28:21 min!
Going to emit links to files with no function:         00:28:55
Launching 32 threads for generating HTML files:        00:28:55

real  37m43.651s
user  112m5.540s
sys   7m39.872s
```

2) Multi-threaded version with 32 CPUs:
```
$ time llvm-cov show -format=html -output-dir=report -instr-profile=... ...
The tool has been launched:                            00:00:00
Loading coverage data:                                 00:00:00
Get unique source files:                               00:00:38
Creating an index out of the source files:             00:00:40
Going into prepareFileReports:                         00:00:40
Preparing file reports using 32 threads:               00:00:40
# Creating thread tasks for the following number of files: 16422
Going to emit summary information for each file:       00:01:57 <-- 1:17 min!
Going to emit links to files with no function:         00:01:58
Launching 32 threads for generating HTML files:        00:01:58

real  11m2.044s
user  134m48.124s
sys   7m53.388s
```

Reviewers: vsk, morehouse

Reviewed By: vsk

Subscribers: Dor1s, llvm-commits, kcc

Differential Revision: https://reviews.llvm.org/D41206

llvm-svn: 321871

10 files changed, 172 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/abs.h b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/abs.h
new file mode 100644
index 00000000000..41eb2b06c0f
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/abs.h
@@ -0,0 +1,7 @@
+template<typename T>
+T abs(T x) {
+  if (x < 0) {
+    return -x;
+  }
+  return x;
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.cc b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.cc
new file mode 100644
index 00000000000..7df13d8d95d
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.cc
@@ -0,0 +1,15 @@
+#include "abs.h"
+#include "bytes.h"
+#include "pow.h"
+
+bool loopBytes() {
+  uint64_t totalInt = 0;
+  double totalFloat = 0;
+  for (uint8_t i = 1; i != 0; ++i) {
+    double a = logarithm(i);
+    a = abs(a);
+    totalInt += abs(pow(i, static_cast<uint8_t>(a)));
+    totalFloat += pow(static_cast<decltype(a)>(i), a);
+  }
+  return totalInt > totalFloat;
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.h b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.h
new file mode 100644
index 00000000000..c239bb64806
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/bytes.h
@@ -0,0 +1,8 @@
+#include <cmath>
+#include <cstdint>
+
+inline double logarithm(uint8_t v) {
+  return log(v);
+}
+
+bool loopBytes();
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.cc b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.cc
new file mode 100644
index 00000000000..b5bc6547c1b
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.cc
@@ -0,0 +1,15 @@
+#include "bytes.h"
+#include "words.h"
+
+int main() {
+  bool result = false;
+  if (loopBytes())
+    result |= true;
+  if (loopWords())
+    result |= true;
+
+  if (result)
+    return 0;
+
+  return result;
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.covmapping b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.covmapping
new file mode 100644
index 00000000000..75bd4cb760b
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.covmapping
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.profdata b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.profdata
new file mode 100644
index 00000000000..21dfdcfddf9
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/main.profdata
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/pow.h b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/pow.h
new file mode 100644
index 00000000000..303d114126d
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/pow.h
@@ -0,0 +1,11 @@
+template<typename T>
+T pow(T b, T p) {
+  if (!p)
+    return 1;
+
+  while (--p) {
+    b *= b;
+  }
+
+  return b;
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.cc b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.cc
new file mode 100644
index 00000000000..7d2b47cf10f
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.cc
@@ -0,0 +1,15 @@
+#include "abs.h"
+#include "bytes.h"
+#include "pow.h"
+
+bool loopWords() {
+  uint64_t totalInt = 0;
+  double totalFloat = 0;
+  for (uint16_t i = 1; i != 0; ++i) {
+    double a = logarithm(i);
+    a = abs(a);
+    totalInt += abs(pow(i, static_cast<uint16_t>(a)));
+    totalFloat += pow(static_cast<decltype(a)>(i), a);
+  }
+  return totalInt > totalFloat;
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.h b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.h
new file mode 100644
index 00000000000..855f7b32e0b
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multithreaded_report/words.h
@@ -0,0 +1,8 @@
+#include <cmath>
+#include <cstdint>
+
+inline double logarithm(uint16_t v) {
+  return log(v);
+}
+
+bool loopWords();
diff --git a/llvm/test/tools/llvm-cov/multithreaded-report.test b/llvm/test/tools/llvm-cov/multithreaded-report.test
new file mode 100644
index 00000000000..d022f2cb850
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/multithreaded-report.test
@@ -0,0 +1,93 @@
+# Test "report" command with and without multiple threads.
+RUN: llvm-cov report -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.1.report
+
+RUN: llvm-cov report -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.2.report
+
+RUN: diff %t.1.report %t.2.report
+
+# Test "export" command with and without multiple threads.
+RUN: llvm-cov export -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.1.json
+
+RUN: llvm-cov export -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.2.json
+
+RUN: diff %t.1.json %t.2.json
+
+# Test "show" command with and without multiple threads, single text file.
+RUN: llvm-cov show -format=text -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.1.text
+
+RUN: llvm-cov show -format=text -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.2.text
+
+RUN: diff %t.1.text %t.2.text
+
+# Test "show" command with and without multiple threads, single HTML file.
+RUN: llvm-cov show -format=html -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.1.html
+
+RUN: llvm-cov show -format=html -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping > %t.2.html
+
+RUN: diff %t.1.html %t.2.html 
+
+# Test "show" command with and without multiple threads, text directory.
+RUN: llvm-cov show -format=text -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping -o %t.1.text_dir
+
+RUN: llvm-cov show -format=text -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping -o %t.2.text_dir
+
+RUN: diff -r %t.1.text_dir %t.2.text_dir
+
+# Test "show" command with and without multiple threads, HTML directory.
+RUN: llvm-cov show -format=html -num-threads=1 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping -o %t.1.html_dir
+
+RUN: llvm-cov show -format=html -num-threads=10 \
+RUN:   -path-equivalence=/tmp,%S/Inputs \
+RUN:   -instr-profile %S/Inputs/multithreaded_report/main.profdata \
+RUN:   %S/Inputs/multithreaded_report/main.covmapping -o %t.2.html_dir
+
+RUN: diff -r %t.1.html_dir %t.2.html_dir
+
+
+Instructions for regenerating the test:
+
+# cd %S/Inputs/multithreaded_report
+
+cp -r . /tmp/multithreaded_report
+
+clang++ -std=c++11 -mllvm -enable-name-compression=false \
+    -fprofile-instr-generate -fcoverage-mapping \
+    /tmp/multithreaded_report/*.cc -o main
+
+LLVM_PROFILE_FILE="main.profraw" ./main
+llvm-profdata merge main.profraw -o main.profdata
+llvm-cov convert-for-testing ./main -o ./main.covmapping
+rm main main.profraw