Check for LLVM 11+ when using -Z instrument-coverage

* `rustc` should now compile under LLVM 9 or 10
* Compiler generates an error if `-Z instrument-coverage` is specified
  but LLVM version is less than 11
* Coverage tests that require `-Z instrument-coverage` and run codegen
  should be skipped if LLVM version is less than 11

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -39,7 +39,7 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
 
     // Encode coverage mappings and generate function records
     let mut function_data = Vec::new();
-    for (instance, function_coverage) in function_coverage_map.into_iter() {
+    for (instance, function_coverage) in function_coverage_map {
         debug!("Generate coverage map for: {:?}", instance);
 
         let mangled_function_name = cx.tcx.symbol_name(instance).to_string();
@@ -172,7 +172,7 @@ impl CoverageMapGenerator {
         // as of `llvm::coverage::CovMapVersion::Version4`.
         let zero_was_n_records_val = cx.const_u32(0);
         let filenames_size_val = cx.const_u32(filenames_size as u32);
-        let zero_was_coverage_size_val = cx.const_u32(0 as u32);
+        let zero_was_coverage_size_val = cx.const_u32(0);
         let version_val = cx.const_u32(coverageinfo::mapping_version());
         let cov_data_header_val = cx.const_struct(
             &[zero_was_n_records_val, filenames_size_val, zero_was_coverage_size_val, version_val],

compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp

@@ -71,7 +71,11 @@ extern "C" void LLVMRustCoverageWriteMapSectionNameToString(LLVMModuleRef M,
 
 extern "C" void LLVMRustCoverageWriteFuncSectionNameToString(LLVMModuleRef M,
                                                              RustStringRef Str) {
+#if LLVM_VERSION_GE(11, 0)
   WriteSectionNameToString(M, IPSK_covfun, Str);
+#else
+  report_fatal_error("rustc option `-Z instrument-coverage` requires LLVM 11 or higher.");
+#endif
 }
 
 extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
@@ -81,5 +85,9 @@ extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
 }
 
 extern "C" uint32_t LLVMRustCoverageMappingVersion() {
+#if LLVM_VERSION_GE(11, 0)
   return coverage::CovMapVersion::Version4;
+#else
+  report_fatal_error("rustc option `-Z instrument-coverage` requires LLVM 11 or higher.");
+#endif
 }

src/test/run-make-fulldeps/coverage-llvmir-base/Makefile

@@ -56,7 +56,14 @@ else
 		-DINSTR_PROF_ORDERFILE='$(DATA_SECTION_PREFIX)__llvm_orderfile'
 endif
 
+ifeq ($(LLVM_VERSION_11_PLUS),false)
+all: test_llvm_ir
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
 all:
+endif
+
+test_llvm_ir:
 	# Compile the test program with non-experimental coverage instrumentation, and generate LLVM IR
 	#
 	# Note: `-Clink-dead-code=no` disables the option, needed because the option is automatically
@@ -68,4 +75,5 @@ all:
 			-Clink-dead-code=$(LINK_DEAD_CODE) \
 			--emit=llvm-ir
 
-	cat "$(TMPDIR)"/testprog.ll | "$(LLVM_FILECHECK)" $(BASEDIR)/filecheck.testprog.txt $(LLVM_FILECHECK_OPTIONS)
+	cat "$(TMPDIR)"/testprog.ll | \
+			"$(LLVM_FILECHECK)" $(BASEDIR)/filecheck.testprog.txt $(LLVM_FILECHECK_OPTIONS)

src/test/run-make-fulldeps/coverage-reports-base/Makefile

@@ -18,7 +18,10 @@ SOURCEDIR=../coverage
 # `llvm/release_debuginfo`. Note that some CI builds disable debug assertions (by setting
 # `NO_LLVM_ASSERTIONS=1`), so it is not OK to fail the test, but `bless`ed test results cannot be
 # generated without debug assertions.
-LLVM_COV_DEBUG := $(shell "$(LLVM_BIN_DIR)"/llvm-cov show --debug 2>&1 | grep -q "Unknown command line argument '--debug'"; echo $$?)
+LLVM_COV_DEBUG := $(shell \
+		"$(LLVM_BIN_DIR)"/llvm-cov show --debug 2>&1 | \
+		grep -q "Unknown command line argument '--debug'"; \
+		echo $$?)
 ifeq ($(LLVM_COV_DEBUG), 1)
 DEBUG_FLAG=--debug
 endif
@@ -30,7 +33,12 @@ ifdef RUSTC_BLESS_TEST
 DEBUG_FLAG=--debug
 endif
 
+ifeq ($(LLVM_VERSION_11_PLUS),true)
 all: $(patsubst $(SOURCEDIR)/%.rs,%,$(wildcard $(SOURCEDIR)/*.rs))
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
+all:
+endif
 
 # Ensure there are no `expected` results for tests that may have been removed or renamed
 .PHONY: clear_expected_if_blessed

src/test/run-make-fulldeps/coverage-spanview-base/Makefile

@@ -24,7 +24,12 @@ For revisions in Pull Requests (PR):
 endef
 export SPANVIEW_HEADER
 
+ifeq ($(LLVM_VERSION_11_PLUS),true)
 all: $(patsubst $(SOURCEDIR)/%.rs,%,$(wildcard $(SOURCEDIR)/*.rs))
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
+all:
+endif
 
 # Ensure there are no `expected` results for tests that may have been removed or renamed
 .PHONY: clear_expected_if_blessed

src/test/run-make-fulldeps/coverage/coverage_tools.mk

@@ -38,6 +38,13 @@ endif
 
 UNAME = $(shell uname)
 
+# Rust option `-Z instrument-coverage` uses LLVM Coverage Mapping Format version 4,
+# which requires LLVM 11 or greater.
+LLVM_VERSION_11_PLUS := $(shell \
+		LLVM_VERSION=$$("$(LLVM_BIN_DIR)"/llvm-config --version) && \
+		LLVM_VERSION_MAJOR=$${LLVM_VERSION/.*/} && \
+		[ $$LLVM_VERSION_MAJOR -ge 11 ] && echo true || echo false)
+
 # FIXME(richkadel): Can any of the features tested by `run-make-fulldeps/coverage-*` tests be tested
 # just as completely by more focused unit tests of the code logic itself, to reduce the number of
 # test result files generated and maintained, and to help identify specific test failures and root