subgroup: add subgroup_broadcast_const variant for pre-spv1.5 broadcasts

Author: Firestar99

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

@@ -281,8 +281,9 @@ pub fn subgroup_all_equal<T: ScalarOrVector>(value: T) -> bool {
 ///
 /// # Safety
 /// * `id` must be dynamically uniform
-/// * before 1.5: `id` must be constant
 /// * Result is undefined if `id` is an inactive invocation or out of bounds
+/// * This variant with a dynamic `id` requires at least `spv1.5` or `vulkan1.2`. Alternatively, you can use
+/// [`subgroup_broadcast_const`] with a constant `id`.
 #[spirv_std_macros::gpu_only]
 #[doc(alias = "OpGroupNonUniformBroadcast")]
 #[inline]
@@ -307,6 +308,48 @@ pub unsafe fn subgroup_broadcast<T: ScalarOrVector>(value: T, id: u32) -> T {
     result
 }
 
+/// Result is the `value` of the invocation identified by the id `id` to all active invocations in the group.
+///
+/// Result Type must be a scalar or vector of floating-point type, integer type, or Boolean type.
+///
+/// Execution is a Scope that identifies the group of invocations affected by this command. It must be Subgroup.
+///
+/// The type of `value` must be the same as Result Type.
+///
+/// `id` must be a scalar of integer type, whose Signedness operand is 0.
+///
+/// Before version 1.5, `id` must come from a constant instruction. Starting with version 1.5, this restriction is lifted. However, behavior is undefined when `id` is not dynamically uniform.
+///
+/// The resulting value is undefined if `id` is an inactive invocation, or is greater than or equal to the size of the group.
+///
+/// Requires Capability `GroupNonUniformBallot`.
+///
+/// # Safety
+/// * Result is undefined if `id` is an inactive invocation or out of bounds
+#[spirv_std_macros::gpu_only]
+#[doc(alias = "OpGroupNonUniformBroadcast")]
+#[inline]
+pub unsafe fn subgroup_broadcast_const<T: ScalarOrVector, const ID: u32>(value: T) -> T {
+    let mut result = T::default();
+
+    unsafe {
+        asm! {
+            "%u32 = OpTypeInt 32 0",
+            "%subgroup = OpConstant %u32 {subgroup}",
+            "%id = OpConstant %u32 {id}",
+            "%value = OpLoad _ {value}",
+            "%result = OpGroupNonUniformBroadcast _ %subgroup %value %id",
+            "OpStore {result} %result",
+            subgroup = const SUBGROUP,
+            value = in(reg) &value,
+            id = const ID,
+            result = in(reg) &mut result,
+        }
+    }
+
+    result
+}
+
 /// Result is the `value` of the invocation from the active invocation with the lowest id in the group to all active invocations in the group.
 ///
 /// Result Type must be a scalar or vector of floating-point type, integer type, or Boolean type.

tests/compiletests/ui/arch/subgroup/subgroup_broadcast.rs

@@ -0,0 +1,25 @@
+// build-pass
+// compile-flags: -C target-feature=+GroupNonUniform,+GroupNonUniformBallot,+ext:SPV_KHR_vulkan_memory_model
+// compile-flags: -C llvm-args=--disassemble-fn=subgroup_broadcast::disassembly
+// normalize-stderr-test "OpLine .*\n" -> ""
+// ignore-vulkan1.0
+// ignore-vulkan1.1
+// ignore-spv1.0
+// ignore-spv1.1
+// ignore-spv1.2
+// ignore-spv1.3
+// ignore-spv1.4
+
+use spirv_std::arch::{GroupOperation, SubgroupMask};
+use spirv_std::spirv;
+
+unsafe fn disassembly(value: i32, id: u32) -> i32 {
+    spirv_std::arch::subgroup_broadcast(value, id)
+}
+
+#[spirv(compute(threads(32, 1, 1)))]
+pub fn main() {
+    unsafe {
+        disassembly(42, 5);
+    }
+}

tests/compiletests/ui/arch/subgroup/subgroup_broadcast.stderr

@@ -0,0 +1,8 @@
+%1 = OpFunction  %2  None %3
+%4 = OpFunctionParameter  %2
+%5 = OpFunctionParameter  %6
+%7 = OpLabel
+%9 = OpGroupNonUniformBroadcast  %2  %10 %4 %5
+OpNoLine
+OpReturnValue %9
+OpFunctionEnd

tests/compiletests/ui/arch/subgroup/subgroup_broadcast_const.rs

@@ -0,0 +1,18 @@
+// build-pass
+// compile-flags: -C target-feature=+GroupNonUniform,+GroupNonUniformBallot,+ext:SPV_KHR_vulkan_memory_model
+// compile-flags: -C llvm-args=--disassemble-fn=subgroup_broadcast_const::disassembly
+// normalize-stderr-test "OpLine .*\n" -> ""
+
+use spirv_std::arch::{GroupOperation, SubgroupMask};
+use spirv_std::spirv;
+
+unsafe fn disassembly(value: i32) -> i32 {
+    spirv_std::arch::subgroup_broadcast_const::<_, 5>(value)
+}
+
+#[spirv(compute(threads(32, 1, 1)))]
+pub fn main() {
+    unsafe {
+        disassembly(-42);
+    }
+}

tests/compiletests/ui/arch/subgroup/subgroup_broadcast_const.stderr

@@ -0,0 +1,7 @@
+%1 = OpFunction  %2  None %3
+%4 = OpFunctionParameter  %2
+%5 = OpLabel
+%7 = OpGroupNonUniformBroadcast  %2  %8 %4 %9
+OpNoLine
+OpReturnValue %7
+OpFunctionEnd

tests/compiletests/ui/arch/subgroup/subgroup_cluster_size_0_fail.stderr

@@ -1,5 +1,5 @@
 error[E0080]: evaluation panicked: `ClusterSize` must be at least 1
-  --> $SPIRV_STD_SRC/arch/subgroup.rs:825:1
+  --> $SPIRV_STD_SRC/arch/subgroup.rs:868:1
    |
 LL | / macro_subgroup_op_clustered!(impl Integer, "OpGroupNonUniformIAdd", subgroup_clustered_i_add; r"
 LL | | An integer add group operation of all `value` operands contributed by active invocations in the group.
@@ -13,7 +13,7 @@ LL | | ");
    = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `macro_subgroup_op_clustered` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
-  --> $SPIRV_STD_SRC/arch/subgroup.rs:825:1
+  --> $SPIRV_STD_SRC/arch/subgroup.rs:868:1
    |
 LL | / macro_subgroup_op_clustered!(impl Integer, "OpGroupNonUniformIAdd", subgroup_clustered_i_add; r"
 LL | | An integer add group operation of all `value` operands contributed by active invocations in the group.

tests/compiletests/ui/arch/subgroup/subgroup_cluster_size_non_power_of_two_fail.stderr

@@ -1,5 +1,5 @@
 error[E0080]: evaluation panicked: `ClusterSize` must be a power of 2
-  --> $SPIRV_STD_SRC/arch/subgroup.rs:825:1
+  --> $SPIRV_STD_SRC/arch/subgroup.rs:868:1
    |
 LL | / macro_subgroup_op_clustered!(impl Integer, "OpGroupNonUniformIAdd", subgroup_clustered_i_add; r"
 LL | | An integer add group operation of all `value` operands contributed by active invocations in the group.
@@ -13,7 +13,7 @@ LL | | ");
    = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `macro_subgroup_op_clustered` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
-  --> $SPIRV_STD_SRC/arch/subgroup.rs:825:1
+  --> $SPIRV_STD_SRC/arch/subgroup.rs:868:1
    |
 LL | / macro_subgroup_op_clustered!(impl Integer, "OpGroupNonUniformIAdd", subgroup_clustered_i_add; r"
 LL | | An integer add group operation of all `value` operands contributed by active invocations in the group.