Don't return the masked range from Scalar::range_metadata

Author: nox

src/librustc/ty/layout.rs

@@ -650,16 +650,22 @@ impl Scalar {
     }
 
     /// Returns a range suitable to be passed to LLVM for range metadata.
-    pub fn range_metadata<C: HasDataLayout>(&self, cx: C) -> Range<u128> {
+    pub fn range_metadata<C: HasDataLayout>(&self, cx: C) -> Option<Range<u128>> {
         // For a (max) value of -1, max will be `-1 as usize`, which overflows.
         // However, that is fine here (it would still represent the full range),
         // i.e., if the range is everything.
         let bits = self.value.size(cx).bits();
         assert!(bits <= 128);
         let mask = !0u128 >> (128 - bits);
-        let start = self.valid_range.start & mask;
-        let end = self.valid_range.end.wrapping_add(1) & mask;
-        start..end
+        let start = self.valid_range.start;
+        let end = self.valid_range.end.wrapping_add(1);
+        if start & mask == end & mask {
+            // The lo==hi case would be rejected by the LLVM verifier
+            // (it would mean either an empty set, which is impossible, or the
+            // entire range of the type, which is pointless).
+            return None;
+        }
+        Some(start..end)
     }
 }
 

src/librustc_trans/abi.rs

@@ -1056,20 +1056,16 @@ impl<'a, 'tcx> FnType<'tcx> {
             _ => {}
         }
         if let layout::Abi::Scalar(ref scalar) = self.ret.layout.abi {
-            let range = scalar.range_metadata(bx.cx);
-            // The lo==hi case would be rejected by the LLVM verifier
-            // (it would mean either an empty set, which is impossible, or the
-            // entire range of the type, which is pointless).
-            //
-            // If the value is a boolean, the range is 0..2 and that ultimately
-            // become 0..0 when the type becomes i1.
-            match scalar.value {
-                layout::Int(..) if !scalar.is_bool() && range.start != range.end => {
-                    // llvm::ConstantRange can deal with ranges that wrap around,
-                    // so an overflow on (max + 1) is fine.
-                    bx.range_metadata(callsite, range);
+            if let Some(range) = scalar.range_metadata(bx.cx) {
+                // If the value is a boolean, the range is 0..2 and that ultimately
+                // become 0..0 when the type becomes i1, which would be rejected
+                // by the LLVM verifier.
+                match scalar.value {
+                    layout::Int(..) if !scalar.is_bool() => {
+                        bx.range_metadata(callsite, range);
+                    }
+                    _ => {}
                 }
-                _ => {}
             }
         }
         for arg in &self.args {

src/librustc_trans/mir/place.rs

@@ -91,20 +91,16 @@ impl<'a, 'tcx> PlaceRef<'tcx> {
         }
 
         let scalar_load_metadata = |load, scalar: &layout::Scalar| {
-            let range = scalar.range_metadata(bx.cx);
-            // The lo==hi case would be rejected by the LLVM verifier
-            // (it would mean either an empty set, which is impossible, or the
-            // entire range of the type, which is pointless).
-            match scalar.value {
-                layout::Int(..) if range.start != range.end => {
-                    // llvm::ConstantRange can deal with ranges that wrap around,
-                    // so an overflow on (max + 1) is fine.
-                    bx.range_metadata(load, range);
-                }
-                layout::Pointer if 0 < range.start && range.start < range.end => {
-                    bx.nonnull_metadata(load);
+            if let Some(range) = scalar.range_metadata(bx.cx) {
+                match scalar.value {
+                    layout::Int(..) => {
+                        bx.range_metadata(load, range);
+                    }
+                    layout::Pointer if 0 < range.start && range.start < range.end => {
+                        bx.nonnull_metadata(load);
+                    }
+                    _ => {}
                 }
-                _ => {}
             }
         };