Auto merge of #114005 - Zalathar:no-cstr, r=jackh726

coverage: Don't convert filename/symbol strings to `CString` for FFI

LLVM APIs are usually perfectly happy to accept pointer/length strings, as long as we supply a suitable length value when creating a `StringRef` or `std::string`.

This lets us avoid quite a few intermediate `CString` copies during coverage codegen. It also lets us use an `IndexSet<Symbol>` (instead of an `IndexSet<CString>`) when building the deduplicated filename table.

1 files changed, 15 insertions, 4 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
index 80b6c0fb439..d61ec0b641c 100644
--- a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
@@ -103,12 +103,20 @@ fromRust(LLVMRustCounterExprKind Kind) {
 }
 
 extern "C" void LLVMRustCoverageWriteFilenamesSectionToBuffer(
-    const char* const Filenames[],
+    const char *const Filenames[],
     size_t FilenamesLen,
+    const size_t *const Lengths,
+    size_t LengthsLen,
     RustStringRef BufferOut) {
+  if (FilenamesLen != LengthsLen) {
+    report_fatal_error(
+        "Mismatched lengths in LLVMRustCoverageWriteFilenamesSectionToBuffer");
+  }
+
   SmallVector<std::string,32> FilenameRefs;
+  FilenameRefs.reserve(FilenamesLen);
   for (size_t i = 0; i < FilenamesLen; i++) {
-    FilenameRefs.push_back(std::string(Filenames[i]));
+    FilenameRefs.emplace_back(Filenames[i], Lengths[i]);
   }
   auto FilenamesWriter =
       coverage::CoverageFilenamesSectionWriter(ArrayRef<std::string>(FilenameRefs));
@@ -153,8 +161,11 @@ extern "C" void LLVMRustCoverageWriteMappingToBuffer(
   CoverageMappingWriter.write(OS);
 }
 
-extern "C" LLVMValueRef LLVMRustCoverageCreatePGOFuncNameVar(LLVMValueRef F, const char *FuncName) {
-  StringRef FuncNameRef(FuncName);
+extern "C" LLVMValueRef LLVMRustCoverageCreatePGOFuncNameVar(
+    LLVMValueRef F,
+    const char *FuncName,
+    size_t FuncNameLen) {
+  StringRef FuncNameRef(FuncName, FuncNameLen);
   return wrap(createPGOFuncNameVar(*cast<Function>(unwrap(F)), FuncNameRef));
 }