Auto merge of #30208 - pnkfelix:fix-issue-30063, r=alexcrichton

When given `rustc -C codegen-units=4 --emit=obj`, reset units back to 1.

Fix #30063

Note: while this code is careful to handle the case of mutliple emit types (e.g. `--emit=asm,obj`) by reporting all the emit types that conflict with codegen units in its warnings, an invocation with multiple emit types *and* `-o PATH` will continue to ignore the requested target path (with a warning), as it already does today, since the code that checks for that is further downstream.  (Multiple emit types without `-o PATH` will "work", though it will downgrade codegen-units to 1 just like all the other cases.)

r? @alexcrichton

src/librustc/session/config.rs

@@ -71,6 +71,30 @@ pub enum OutputType {
     DepInfo,
 }
 
+impl OutputType {
+    fn is_compatible_with_codegen_units_and_single_output_file(&self) -> bool {
+        match *self {
+            OutputType::Exe |
+            OutputType::DepInfo => true,
+            OutputType::Bitcode |
+            OutputType::Assembly |
+            OutputType::LlvmAssembly |
+            OutputType::Object => false,
+        }
+    }
+
+    fn shorthand(&self) -> &'static str {
+        match *self {
+            OutputType::Bitcode => "llvm-bc",
+            OutputType::Assembly => "asm",
+            OutputType::LlvmAssembly => "llvm-ir",
+            OutputType::Object => "obj",
+            OutputType::Exe => "link",
+            OutputType::DepInfo => "dep-info",
+        }
+    }
+}
+
 #[derive(Clone)]
 pub struct Options {
     // The crate config requested for the session, which may be combined
@@ -933,7 +957,28 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         output_types.insert(OutputType::Exe, None);
     }
 
-    let cg = build_codegen_options(matches, color);
+    let mut cg = build_codegen_options(matches, color);
+
+    // Issue #30063: if user requests llvm-related output to one
+    // particular path, disable codegen-units.
+    if matches.opt_present("o") && cg.codegen_units != 1 {
+        let incompatible: Vec<_> = output_types.iter()
+            .map(|ot_path| ot_path.0)
+            .filter(|ot| {
+                !ot.is_compatible_with_codegen_units_and_single_output_file()
+            }).collect();
+        if !incompatible.is_empty() {
+            for ot in &incompatible {
+                early_warn(color, &format!("--emit={} with -o incompatible with \
+                                            -C codegen-units=N for N > 1",
+                                           ot.shorthand()));
+            }
+            early_warn(color, "resetting to default -C codegen-units=1");
+            cg.codegen_units = 1;
+        }
+    }
+
+    let cg = cg;
 
     let sysroot_opt = matches.opt_str("sysroot").map(|m| PathBuf::from(&m));
     let target = matches.opt_str("target").unwrap_or(

src/test/run-make/issue-30063/Makefile

@@ -0,0 +1,35 @@
+-include ../tools.mk
+
+all:
+	rm -f $(TMPDIR)/foo-output
+	$(RUSTC) -C codegen-units=4 -o $(TMPDIR)/foo-output foo.rs
+	rm $(TMPDIR)/foo-output
+
+	rm -f $(TMPDIR)/asm-output
+	$(RUSTC) -C codegen-units=4 --emit=asm -o $(TMPDIR)/asm-output foo.rs
+	rm $(TMPDIR)/asm-output
+
+	rm -f $(TMPDIR)/bc-output
+	$(RUSTC) -C codegen-units=4 --emit=llvm-bc -o $(TMPDIR)/bc-output foo.rs
+	rm $(TMPDIR)/bc-output
+
+	rm -f $(TMPDIR)/ir-output
+	$(RUSTC) -C codegen-units=4 --emit=llvm-ir -o $(TMPDIR)/ir-output foo.rs
+	rm $(TMPDIR)/ir-output
+
+	rm -f $(TMPDIR)/link-output
+	$(RUSTC) -C codegen-units=4 --emit=link -o $(TMPDIR)/link-output foo.rs
+	rm $(TMPDIR)/link-output
+
+	rm -f $(TMPDIR)/obj-output
+	$(RUSTC) -C codegen-units=4 --emit=obj -o $(TMPDIR)/obj-output foo.rs
+	rm $(TMPDIR)/obj-output
+
+	rm -f $(TMPDIR)/dep-output
+	$(RUSTC) -C codegen-units=4 --emit=dep-info -o $(TMPDIR)/dep-output foo.rs
+	rm $(TMPDIR)/dep-output
+
+#	# (This case doesn't work yet, and may be fundamentally wrong-headed anyway.)
+#	rm -f $(TMPDIR)/multi-output
+#	$(RUSTC) -C codegen-units=4 --emit=asm,obj -o $(TMPDIR)/multi-output foo.rs
+#	rm $(TMPDIR)/multi-output

src/test/run-make/issue-30063/foo.rs

@@ -0,0 +1,11 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() { }