[clang][deps] Reset some benign codegen options

Some command-line codegen arguments are likely to differ between identical modules discovered from different translation units. This patch removes them to make builds deterministic and/or reduce the number of built modules.

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D112923

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -37,9 +37,13 @@ CompilerInvocation ModuleDepCollector::makeInvocationForModuleBuildWithoutPaths(
   CI.getLangOpts()->resetNonModularOptions();
   CI.getPreprocessorOpts().resetNonModularOptions();
 
-  // Remove options incompatible with explicit module build.
+  // Remove options incompatible with explicit module build or are likely to
+  // differ between identical modules discovered from different translation
+  // units.
   CI.getFrontendOpts().Inputs.clear();
   CI.getFrontendOpts().OutputFile.clear();
+  CI.getCodeGenOpts().MainFileName.clear();
+  CI.getCodeGenOpts().DwarfDebugFlags.clear();
 
   CI.getFrontendOpts().ProgramAction = frontend::GenerateModule;
   CI.getLangOpts()->ModuleName = Deps.ID.ModuleName;

clang/test/ClangScanDeps/Inputs/removed-args/cdb.json.template

@@ -1,7 +1,7 @@
 [
   {
     "directory": "DIR",
-    "command": "clang -fsyntax-only DIR/tu.c -fmodules -fimplicit-module-maps -fmodules-cache-path=DIR/cache -include DIR/header.h -o DIR/tu.o",
+    "command": "clang -fsyntax-only DIR/tu.c -fmodules -fimplicit-module-maps -fmodules-cache-path=DIR/cache -include DIR/header.h -grecord-command-line -o DIR/tu.o",
     "file": "DIR/tu.c"
   }
 ]

clang/test/ClangScanDeps/removed-args.c

@@ -1,6 +1,8 @@
 // Some command-line arguments used for compiling translation units are not
-// compatible with the semantics of modules and should be removed. In this test
-// case, the command-lines for modules should drop the '-include' argument.
+// compatible with the semantics of modules or are likely to differ between
+// identical modules discovered from different translation units. This test
+// checks such arguments are removed from the command-lines: '-include',
+// '-dwarf-debug-flag' and '-main-file-name'.
 
 // RUN: rm -rf %t && mkdir %t
 // RUN: cp %S/Inputs/removed-args/* %t
@@ -18,6 +20,8 @@
 // CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/module.modulemap",
 // CHECK-NEXT:       "command-line": [
 // CHECK-NEXT:         "-cc1"
+// CHECK-NOT:          "-dwarf-debug-flags"
+// CHECK-NOT:          "-main-file-name"
 // CHECK-NOT:          "-include"
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[HASH_MOD_HEADER:.*]]",