Warn on redundant --cfg directive when revisions are used

Author: clubby789

Diff for: src/tools/compiletest/src/runtest.rs

@@ -468,7 +468,13 @@ impl<'test> TestCx<'test> {
 
         if let Some(revision) = self.revision {
             let normalized_revision = normalize_revision(revision);
-            cmd.args(&["--cfg", &normalized_revision]);
+            let cfg_arg = ["--cfg", &normalized_revision];
+            if self.props.compile_flags.windows(2).any(|args| args == cfg_arg) {
+                panic!(
+                    "warning: redundant cfg argument `{normalized_revision}` is already created by the revision"
+                );
+            }
+            cmd.args(cfg_arg);
         }
 
         if !self.props.no_auto_check_cfg {

Diff for: tests/ui/precondition-checks/layout.rs

@@ -2,8 +2,6 @@
 //@ compile-flags: -Copt-level=3 -Cdebug-assertions=no -Zub-checks=yes
 //@ error-pattern: unsafe precondition(s) violated: Layout::from_size_align_unchecked requires
 //@ revisions: toolarge badalign
-//@[toolarge] compile-flags: --cfg toolarge
-//@[badalign] compile-flags: --cfg badalign
 
 fn main() {
     unsafe {

Diff for: tests/ui/sanitizer/cfg.rs

@@ -5,19 +5,19 @@
 //@ revisions: address cfi kcfi leak memory thread
 //@compile-flags: -Ctarget-feature=-crt-static
 //@[address]needs-sanitizer-address
-//@[address]compile-flags: -Zsanitizer=address --cfg address
+//@[address]compile-flags: -Zsanitizer=address
 //@[cfi]needs-sanitizer-cfi
-//@[cfi]compile-flags:     -Zsanitizer=cfi     --cfg cfi
+//@[cfi]compile-flags:     -Zsanitizer=cfi
 //@[cfi]compile-flags:     -Clto -Ccodegen-units=1
 //@[kcfi]needs-llvm-components: x86
-//@[kcfi]compile-flags:    -Zsanitizer=kcfi    --cfg kcfi --target x86_64-unknown-none
+//@[kcfi]compile-flags:    -Zsanitizer=kcfi --target x86_64-unknown-none
 //@[kcfi]compile-flags:    -C panic=abort
 //@[leak]needs-sanitizer-leak
-//@[leak]compile-flags:    -Zsanitizer=leak    --cfg leak
+//@[leak]compile-flags:    -Zsanitizer=leak
 //@[memory]needs-sanitizer-memory
-//@[memory]compile-flags:  -Zsanitizer=memory  --cfg memory
+//@[memory]compile-flags:  -Zsanitizer=memory
 //@[thread]needs-sanitizer-thread
-//@[thread]compile-flags:  -Zsanitizer=thread  --cfg thread
+//@[thread]compile-flags:  -Zsanitizer=thread
 
 #![feature(cfg_sanitize, no_core, lang_items)]
 #![crate_type="lib"]