asm: implicit label after return or abort terminator

crates/rustc_codegen_spirv/src/builder/spirv_asm.rs

@@ -3,7 +3,7 @@ use crate::builder_spirv::{BuilderCursor, SpirvValue};
 use crate::codegen_cx::CodegenCx;
 use crate::spirv_type::SpirvType;
 use rspirv::dr;
-use rspirv::grammar::{LogicalOperand, OperandKind, OperandQuantifier};
+use rspirv::grammar::{reflect, LogicalOperand, OperandKind, OperandQuantifier};
 use rspirv::spirv::{
     FPFastMathMode, FragmentShadingRate, FunctionControl, ImageOperands, KernelProfilingInfo,
     LoopControl, MemoryAccess, MemorySemantics, Op, RayFlags, SelectionControl, StorageClass, Word,
@@ -70,8 +70,13 @@ impl<'a, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'tcx> {
         options: InlineAsmOptions,
         _line_spans: &[Span],
     ) {
-        if !options.is_empty() {
-            self.err(&format!("asm flags not supported: {:?}", options));
+        const SUPPORTED_OPTIONS: InlineAsmOptions = InlineAsmOptions::NORETURN;
+        let unsupported_options = options & !SUPPORTED_OPTIONS;
+        if !unsupported_options.is_empty() {
+            self.err(&format!(
+                "asm flags not supported: {:?}",
+                unsupported_options
+            ));
         }
         // vec of lines, and each line is vec of tokens
         let mut tokens = vec![vec![]];
@@ -328,10 +333,24 @@ impl<'cx, 'tcx> Builder<'cx, 'tcx> {
                 }
                 return;
             }
-            _ => {
+
+            op => {
                 self.emit()
                     .insert_into_block(dr::InsertPoint::End, inst)
                     .unwrap();
+
+                // Return or abort terminators will also end the current block and start a new one.
+                // The new block is transparent to the actual builder cursor.
+                if reflect::is_return_or_abort(op) {
+                    let label = self.emit().id();
+                    self.emit()
+                        .insert_into_block(
+                            dr::InsertPoint::End,
+                            dr::Instruction::new(Op::Label, None, Some(label), vec![]),
+                        )
+                        .unwrap();
+                }
+
                 return;
             }
         };

crates/spirv-std/src/arch.rs

@@ -148,8 +148,5 @@ pub unsafe fn vector_insert_dynamic<T: Scalar, V: Vector<T, N>, const N: usize>(
 #[doc(alias = "OpKill", alias = "discard")]
 #[allow(clippy::empty_loop)]
 pub fn kill() -> ! {
-    unsafe {
-        asm!("OpKill", "%unused = OpLabel");
-    }
-    loop {}
+    unsafe { asm!("OpKill", options(noreturn)) }
 }

crates/spirv-std/src/arch/ray_tracing.rs

@@ -44,8 +44,7 @@ pub unsafe fn report_intersection(hit: f32, hit_kind: u32) -> bool {
 #[inline]
 #[allow(clippy::empty_loop)]
 pub unsafe fn ignore_intersection() -> ! {
-    asm!("OpIgnoreIntersectionKHR", "%unused = OpLabel");
-    loop {}
+    asm!("OpIgnoreIntersectionKHR", options(noreturn));
 }
 
 /// Terminates the invocation that executes it, stops the ray traversal, accepts
@@ -57,8 +56,7 @@ pub unsafe fn ignore_intersection() -> ! {
 #[inline]
 #[allow(clippy::empty_loop)]
 pub unsafe fn terminate_ray() -> ! {
-    asm!("OpTerminateRayKHR", "%unused = OpLabel");
-    loop {}
+    asm!("OpTerminateRayKHR", options(noreturn));
 }
 
 /// Invoke a callable shader.

crates/spirv-std/src/lib.rs

@@ -118,7 +118,7 @@ pub use glam;
 #[cfg(all(not(test), target_arch = "spirv"))]
 #[panic_handler]
 fn panic(_: &core::panic::PanicInfo<'_>) -> ! {
-    loop {}
+    unsafe { asm!("", options(noreturn)) }
 }
 
 #[cfg(all(not(test), target_arch = "spirv"))]

crates/spirv-std/src/ray_tracing.rs

@@ -25,10 +25,9 @@ impl AccelerationStructure {
             "%ret = OpTypeAccelerationStructureKHR",
             "%result = OpConvertUToAccelerationStructureKHR %ret {id}",
             "OpReturnValue %result",
-            "%blah = OpLabel",
             id = in(reg) id,
+            options(noreturn)
         }
-        loop {}
     }
 
     /// Converts a vector of two 32 bit integers into an [`AccelerationStructure`].
@@ -47,10 +46,9 @@ impl AccelerationStructure {
             "%id = OpLoad _ {id}",
             "%result = OpConvertUToAccelerationStructureKHR %ret %id",
             "OpReturnValue %result",
-            "%blah = OpLabel",
             id = in(reg) &id,
+            options(noreturn),
         }
-        loop {}
     }
 
     #[spirv_std_macros::gpu_only]

crates/spirv-std/src/runtime_array.rs

@@ -17,11 +17,10 @@ impl<T> RuntimeArray<T> {
         asm! {
             "%result = OpAccessChain _ {arr} {index}",
             "OpReturnValue %result",
-            "%unused = OpLabel",
             arr = in(reg) self,
             index = in(reg) index,
+            options(noreturn),
         }
-        loop {}
     }
 
     #[spirv_std_macros::gpu_only]
@@ -30,10 +29,9 @@ impl<T> RuntimeArray<T> {
         asm! {
             "%result = OpAccessChain _ {arr} {index}",
             "OpReturnValue %result",
-            "%unused = OpLabel",
             arr = in(reg) self,
             index = in(reg) index,
+            options(noreturn),
         }
-        loop {}
     }
 }