Add path remapping with -coverage-prefix-map to coverage data

Previously the path to covered files in the __LLVM_COV / __llvm_covmap
section were absolute. This made remote builds with coverage information
difficult because all machines would have to have the same build root.
This change uses the values for `-coverage-prefix-map` to remap files in
the coverage info to relative paths. These paths work correctly with
llvm-cov when it is run from the same source directory as the
compilation, or from a different directory using the `-path-equivalence`
argument.

This is analogous to this change in clang https://reviews.llvm.org/D81122

Author: keith

include/swift/AST/DiagnosticsFrontend.def

@@ -305,6 +305,9 @@ ERROR(error_optimization_remark_pattern, none, "%0 in '%1'",
 ERROR(error_invalid_debug_prefix_map, none,
       "invalid argument '%0' to -debug-prefix-map; it must be of the form "
       "'original=remapped'", (StringRef))
+ERROR(error_invalid_coverage_prefix_map, none,
+      "invalid argument '%0' to -coverage-prefix-map; it must be of the form "
+      "'original=remapped'", (StringRef))
 
 
 ERROR(error_unable_to_write_swift_ranges_file, none,

include/swift/AST/IRGenOptions.h

@@ -169,6 +169,9 @@ class IRGenOptions {
   /// Path prefixes that should be rewritten in debug info.
   PathRemapper DebugPrefixMap;
 
+  /// Path prefixes that should be rewritten in coverage info.
+  PathRemapper CoveragePrefixMap;
+
   /// What level of debug info to generate.
   IRGenDebugInfoLevel DebugInfoLevel : 2;
 

include/swift/Option/Options.td

@@ -698,6 +698,9 @@ def gdwarf_types : Flag<["-"], "gdwarf-types">,
 def debug_prefix_map : Separate<["-"], "debug-prefix-map">,
     Flags<[FrontendOption]>,
     HelpText<"Remap source paths in debug info">;
+def coverage_prefix_map : Separate<["-"], "coverage-prefix-map">,
+  Flags<[FrontendOption]>,
+  HelpText<"Remap source paths in coverage info">;
 
 def debug_info_format : Joined<["-"], "debug-info-format=">,
   Flags<[FrontendOption]>,

lib/Driver/Driver.cpp

@@ -179,6 +179,12 @@ static void validateDebugInfoArgs(DiagnosticEngine &diags,
   for (auto A : args.getAllArgValues(options::OPT_debug_prefix_map))
     if (A.find('=') == StringRef::npos)
       diags.diagnose(SourceLoc(), diag::error_invalid_debug_prefix_map, A);
+
+  // Check for any -coverage-prefix-map options that aren't of the form
+  // 'original=remapped' (either side can be empty, however).
+  for (auto A : args.getAllArgValues(options::OPT_coverage_prefix_map))
+    if (A.find('=') == StringRef::npos)
+      diags.diagnose(SourceLoc(), diag::error_invalid_coverage_prefix_map, A);
 }
 
 static void validateVerifyIncrementalDependencyArgs(DiagnosticEngine &diags,

lib/Driver/ToolChains.cpp

@@ -260,6 +260,7 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
 
   // Pass on file paths that should be remapped in debug info.
   inputArgs.AddAllArgs(arguments, options::OPT_debug_prefix_map);
+  inputArgs.AddAllArgs(arguments, options::OPT_coverage_prefix_map);
 
   // Pass through the values passed to -Xfrontend.
   inputArgs.AddAllArgValues(arguments, options::OPT_Xfrontend);

lib/Frontend/CompilerInvocation.cpp

@@ -1249,6 +1249,11 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
     Opts.DebugPrefixMap.addMapping(SplitMap.first, SplitMap.second);
   }
 
+  for (auto A : Args.getAllArgValues(options::OPT_coverage_prefix_map)) {
+    auto SplitMap = StringRef(A).split('=');
+    Opts.CoveragePrefixMap.addMapping(SplitMap.first, SplitMap.second);
+  }
+
   for (const Arg *A : Args.filtered(OPT_Xcc)) {
     StringRef Opt = A->getValue();
     if (Opt.startswith("-D") || Opt.startswith("-U"))

lib/IRGen/GenCoverage.cpp

@@ -18,6 +18,7 @@
 #include "IRGenModule.h"
 #include "SwiftTargetInfo.h"
 
+#include "swift/AST/IRGenOptions.h"
 #include "swift/SIL/SILModule.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Module.h"
@@ -60,6 +61,7 @@ void IRGenModule::emitCoverageMapping() {
     if (std::find(Files.begin(), Files.end(), M->getFile()) == Files.end())
       Files.push_back(M->getFile());
 
+  auto remapper = getOptions().CoveragePrefixMap;
   // Awkwardly munge absolute filenames into a vector of StringRefs.
   // TODO: This is heinous - the same thing is happening in clang, but the API
   // really needs to be cleaned up for both.
@@ -68,7 +70,7 @@ void IRGenModule::emitCoverageMapping() {
   for (StringRef Name : Files) {
     llvm::SmallString<256> Path(Name);
     llvm::sys::fs::make_absolute(Path);
-    FilenameStrs.push_back(std::string(Path.begin(), Path.end()));
+    FilenameStrs.push_back(remapper.remapPath(Path));
     FilenameRefs.push_back(FilenameStrs.back());
   }
 

test/Driver/coverage-prefix-map.swift

@@ -0,0 +1,9 @@
+// RUN: not %target-swiftc_driver -coverage-prefix-map old %s 2>&1 | %FileCheck %s -check-prefix CHECK-INVALID
+// RUN: %target-swiftc_driver -### -coverage-prefix-map old=new %s 2>&1 | %FileCheck %s -check-prefix CHECK-SIMPLE
+// RUN: %target-swiftc_driver -### -coverage-prefix-map old=n=ew %s 2>&1 | %FileCheck %s -check-prefix CHECK-COMPLEX
+// RUN: %target-swiftc_driver -### -coverage-prefix-map old= %s 2>&1 | %FileCheck %s -check-prefix CHECK-EMPTY
+
+// CHECK-INVALID: error: invalid argument 'old' to -coverage-prefix-map
+// CHECK-SIMPLE: coverage-prefix-map old=new
+// CHECK-COMPLEX: coverage-prefix-map old=n=ew
+// CHECK-EMPTY: coverage-prefix-map old=

test/Profiler/coverage_relative_path.swift

@@ -0,0 +1,16 @@
+// %s expands to an absolute path, so to test relative paths we need to create a
+// clean directory, put the source there, and cd into it.
+// RUN: rm -rf %t
+// RUN: mkdir -p %t/foo/bar/baz
+// RUN: echo "func coverage() {}" > %t/foo/bar/baz/coverage_relative_path.swift
+// RUN: cd %t/foo/bar
+
+// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -Xllvm -enable-name-compression=false -emit-ir %/t/foo/bar/baz/coverage_relative_path.swift | %FileCheck -check-prefix=ABSOLUTE %s
+//
+// ABSOLUTE: @__llvm_coverage_mapping = {{.*"\\01.*foo.*bar.*baz.*coverage_relative_path\.swift}}
+
+// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -Xllvm -enable-name-compression=false -coverage-prefix-map %/t/foo/bar=. -emit-ir %/t/foo/bar/baz/coverage_relative_path.swift | %FileCheck -check-prefix=RELATIVE %s
+//
+// RELATIVE: @__llvm_coverage_mapping = {{.*"\\01[^/]*}}.{{/|\\}}baz{{.*coverage_relative_path\.swift}}
+
+func coverage() {}