Attempt to fix intermittent failures of pgo-branch-weights test.

src/test/run-make-fulldeps/pgo-branch-weights/Makefile

@@ -15,21 +15,29 @@ ifdef IS_MSVC
 COMMON_FLAGS=-Cpanic=abort
 endif
 
+# For some very small programs GNU ld seems to not properly handle
+# instrumentation sections correctly. Neither Gold nor LLD have that problem.
+ifeq ($(UNAME),Linux)
+ifneq (,$(findstring x86,$(TARGET)))
+COMMON_FLAGS=-Clink-args=-fuse-ld=gold
+endif
+endif
+
+
 all:
 	# We don't compile `opaque` with either optimizations or instrumentation.
-	# We don't compile `opaque` with either optimizations or instrumentation.
-	$(RUSTC) $(COMMON_FLAGS) opaque.rs
+	$(RUSTC) $(COMMON_FLAGS) opaque.rs || exit 1
 	# Compile the test program with instrumentation
-	mkdir -p "$(TMPDIR)"/prof_data_dir
+	mkdir -p "$(TMPDIR)/prof_data_dir" || exit 1
 	$(RUSTC) $(COMMON_FLAGS) interesting.rs \
-		-Cprofile-generate="$(TMPDIR)"/prof_data_dir -O -Ccodegen-units=1
-	$(RUSTC) $(COMMON_FLAGS) main.rs -Cprofile-generate="$(TMPDIR)"/prof_data_dir -O
+		-Cprofile-generate="$(TMPDIR)/prof_data_dir" -O -Ccodegen-units=1 || exit 1
+	$(RUSTC) $(COMMON_FLAGS) main.rs -Cprofile-generate="$(TMPDIR)/prof_data_dir" -O || exit 1
 	# The argument below generates to the expected branch weights
 	$(call RUN,main aaaaaaaaaaaa2bbbbbbbbbbbb2bbbbbbbbbbbbbbbbcc) || exit 1
-	"$(LLVM_BIN_DIR)"/llvm-profdata merge \
-		-o "$(TMPDIR)"/prof_data_dir/merged.profdata \
-		"$(TMPDIR)"/prof_data_dir
+	"$(LLVM_BIN_DIR)/llvm-profdata" merge \
+		-o "$(TMPDIR)/prof_data_dir/merged.profdata" \
+		"$(TMPDIR)/prof_data_dir" || exit 1
 	$(RUSTC) $(COMMON_FLAGS) interesting.rs \
-		-Cprofile-use="$(TMPDIR)"/prof_data_dir/merged.profdata -O \
-		-Ccodegen-units=1 --emit=llvm-ir
-	cat "$(TMPDIR)"/interesting.ll | "$(LLVM_FILECHECK)" filecheck-patterns.txt
+		-Cprofile-use="$(TMPDIR)/prof_data_dir/merged.profdata" -O \
+		-Ccodegen-units=1 --emit=llvm-ir || exit 1
+	cat "$(TMPDIR)/interesting.ll" | "$(LLVM_FILECHECK)" filecheck-patterns.txt