shared: only retain entry point vars with preserve-bindings

Firestar99 · Firestar99 · commit f1ea8a796e61 · 2025-11-03T15:03:16.000+01:00
diff --git a/crates/rustc_codegen_spirv/src/linker/entry_interface.rs b/crates/rustc_codegen_spirv/src/linker/entry_interface.rs
@@ -13,7 +13,7 @@ type Id = Word;
 ///
 /// This is needed for (arguably-not-interface) `Private` in SPIR-V >= 1.4,
 /// but also any interface variables declared "out of band" (e.g. via `asm!`).
-pub fn gather_all_interface_vars_from_uses(module: &mut Module) {
+pub fn gather_all_interface_vars_from_uses(module: &mut Module, preserve_bindings: bool) {
     // Start by mapping out which global (i.e. `OpVariable` or constants) IDs
     // can be used to access any interface-relevant `OpVariable`s
     // (where "interface-relevant" depends on the version, see comments below).
@@ -87,12 +87,15 @@ pub fn gather_all_interface_vars_from_uses(module: &mut Module) {
             entry.operands[1].unwrap_id_ref()
         );
 
-        // NOTE(eddyb) it might be better to remove any unused vars, or warn
-        // the user about their presence, but for now this keeps them around.
-        let mut interface_vars: IndexSet<Id> = entry.operands[3..]
-            .iter()
-            .map(|operand| operand.unwrap_id_ref())
-            .collect();
+        // `preserve_bindings` retains any declared entry point vars, otherwise we may DCE them
+        let mut interface_vars: IndexSet<Id> = if preserve_bindings {
+            entry.operands[3..]
+                .iter()
+                .map(|operand| operand.unwrap_id_ref())
+                .collect()
+        } else {
+            IndexSet::default()
+        };
 
         interface_vars.extend(&used_vars_per_fn_idx[entry_func_idx]);
 
diff --git a/crates/rustc_codegen_spirv/src/linker/mod.rs b/crates/rustc_codegen_spirv/src/linker/mod.rs
@@ -654,7 +654,7 @@ pub fn link(
 
     {
         let _timer = sess.timer("link_gather_all_interface_vars_from_uses");
-        entry_interface::gather_all_interface_vars_from_uses(&mut output);
+        entry_interface::gather_all_interface_vars_from_uses(&mut output, opts.preserve_bindings);
     }
 
     if opts.spirv_metadata == SpirvMetadata::NameVariables {
diff --git a/tests/compiletests/ui/arch/shared/dce_shared.stderr b/tests/compiletests/ui/arch/shared/dce_shared.stderr
@@ -1,40 +1,35 @@
 OpCapability Shader
 OpMemoryModel Logical Simple
-OpEntryPoint GLCompute %1 "main" %2 %3 %4 %5 %6
+OpEntryPoint GLCompute %1 "main" %2 %3 %4 %5
 OpExecutionMode %1 LocalSize 2 1 1
 OpName %2 "input"
 OpName %3 "output"
-OpName %6 "inv_id"
-OpName %4 "used_shared"
-OpName %5 "dce_shared"
-OpDecorate %9 Block
-OpMemberDecorate %9 0 Offset 0
+OpName %4 "inv_id"
+OpName %5 "used_shared"
+OpDecorate %8 Block
+OpMemberDecorate %8 0 Offset 0
 OpDecorate %2 NonWritable
 OpDecorate %2 Binding 0
 OpDecorate %2 DescriptorSet 0
 OpDecorate %3 Binding 1
 OpDecorate %3 DescriptorSet 0
-OpDecorate %6 BuiltIn LocalInvocationIndex
-%10 = OpTypeFloat 32
-%9 = OpTypeStruct %10
-%11 = OpTypePointer StorageBuffer %9
-%12 = OpTypePointer Workgroup %10
-%13 = OpTypeInt 32 1
-%14 = OpTypeInt 32 0
-%15 = OpConstant  %14  2
-%16 = OpTypeArray %13 %15
-%17 = OpTypePointer Workgroup %16
-%18 = OpTypeVector %14 3
-%19 = OpTypePointer Input %18
-%20 = OpTypeVoid
-%21 = OpTypeFunction %20
-%22 = OpTypePointer StorageBuffer %10
-%2 = OpVariable  %11  StorageBuffer
-%23 = OpConstant  %14  0
-%3 = OpVariable  %11  StorageBuffer
-%6 = OpVariable  %19  Input
-%24 = OpTypeBool
-%4 = OpVariable  %12  Workgroup
-%25 = OpConstant  %14  264
-%26 = OpConstant  %14  1
-%5 = OpVariable  %17  Workgroup
+OpDecorate %4 BuiltIn LocalInvocationIndex
+%9 = OpTypeFloat 32
+%8 = OpTypeStruct %9
+%10 = OpTypePointer StorageBuffer %8
+%11 = OpTypePointer Workgroup %9
+%12 = OpTypeInt 32 0
+%13 = OpConstant  %12  2
+%14 = OpTypeVector %12 3
+%15 = OpTypePointer Input %14
+%16 = OpTypeVoid
+%17 = OpTypeFunction %16
+%18 = OpTypePointer StorageBuffer %9
+%2 = OpVariable  %10  StorageBuffer
+%19 = OpConstant  %12  0
+%3 = OpVariable  %10  StorageBuffer
+%4 = OpVariable  %15  Input
+%20 = OpTypeBool
+%5 = OpVariable  %11  Workgroup
+%21 = OpConstant  %12  264
+%22 = OpConstant  %12  1
diff --git a/tests/compiletests/ui/dis/issue-723-output.stderr b/tests/compiletests/ui/dis/issue-723-output.stderr
@@ -1,13 +1,8 @@
 OpCapability Shader
 OpMemoryModel Logical Simple
-OpEntryPoint Fragment %1 "main" %2
+OpEntryPoint Fragment %1 "main"
 OpExecutionMode %1 OriginUpperLeft
-%3 = OpString "$DIR/issue-723-output.rs"
-OpName %4 "issue_723_output::main"
-OpDecorate %2 Location 0
-%5 = OpTypeFloat 32
-%6 = OpTypeVector %5 4
-%7 = OpTypePointer Output %6
-%8 = OpTypeVoid
-%9 = OpTypeFunction %8
-%2 = OpVariable  %7  Output
+%2 = OpString "$DIR/issue-723-output.rs"
+OpName %3 "issue_723_output::main"
+%4 = OpTypeVoid
+%5 = OpTypeFunction %4
diff --git a/tests/compiletests/ui/dis/scalars.supported.stderr b/tests/compiletests/ui/dis/scalars.supported.stderr
@@ -7,37 +7,37 @@ OpMemoryModel Logical Simple
 OpEntryPoint Fragment %1 "main" %2 %3 %4 %5 %6 %7 %8 %9 %10 %11 %12
 OpExecutionMode %1 OriginUpperLeft
 %13 = OpString "$DIR/scalars.rs"
-OpName %3 "in_u8"
-OpName %4 "in_u16"
-OpName %5 "in_u32"
-OpName %6 "in_u64"
-OpName %7 "in_i8"
-OpName %8 "in_i16"
-OpName %9 "in_i32"
-OpName %10 "in_i64"
-OpName %11 "in_f32"
-OpName %12 "in_f64"
-OpName %2 "out"
+OpName %2 "in_u8"
+OpName %3 "in_u16"
+OpName %4 "in_u32"
+OpName %5 "in_u64"
+OpName %6 "in_i8"
+OpName %7 "in_i16"
+OpName %8 "in_i32"
+OpName %9 "in_i64"
+OpName %10 "in_f32"
+OpName %11 "in_f64"
+OpName %12 "out"
+OpDecorate %2 Flat
+OpDecorate %2 Location 0
 OpDecorate %3 Flat
-OpDecorate %3 Location 0
+OpDecorate %3 Location 1
 OpDecorate %4 Flat
-OpDecorate %4 Location 1
+OpDecorate %4 Location 2
 OpDecorate %5 Flat
-OpDecorate %5 Location 2
+OpDecorate %5 Location 3
 OpDecorate %6 Flat
-OpDecorate %6 Location 3
+OpDecorate %6 Location 4
 OpDecorate %7 Flat
-OpDecorate %7 Location 4
+OpDecorate %7 Location 5
 OpDecorate %8 Flat
-OpDecorate %8 Location 5
+OpDecorate %8 Location 6
 OpDecorate %9 Flat
-OpDecorate %9 Location 6
-OpDecorate %10 Flat
-OpDecorate %10 Location 7
-OpDecorate %11 Location 8
-OpDecorate %12 Flat
-OpDecorate %12 Location 9
-OpDecorate %2 Location 0
+OpDecorate %9 Location 7
+OpDecorate %10 Location 8
+OpDecorate %11 Flat
+OpDecorate %11 Location 9
+OpDecorate %12 Location 0
 %14 = OpTypeInt 32 0
 %15 = OpTypePointer Output %14
 %16 = OpTypeInt 8 0
@@ -61,18 +61,18 @@ OpDecorate %2 Location 0
 %34 = OpTypePointer Input %33
 %35 = OpTypeVoid
 %36 = OpTypeFunction %35
-%3 = OpVariable  %17  Input
-%4 = OpVariable  %19  Input
-%5 = OpVariable  %20  Input
-%6 = OpVariable  %22  Input
-%7 = OpVariable  %24  Input
-%8 = OpVariable  %26  Input
-%9 = OpVariable  %28  Input
-%10 = OpVariable  %30  Input
-%11 = OpVariable  %32  Input
-%12 = OpVariable  %34  Input
+%2 = OpVariable  %17  Input
+%3 = OpVariable  %19  Input
+%4 = OpVariable  %20  Input
+%5 = OpVariable  %22  Input
+%6 = OpVariable  %24  Input
+%7 = OpVariable  %26  Input
+%8 = OpVariable  %28  Input
+%9 = OpVariable  %30  Input
+%10 = OpVariable  %32  Input
+%11 = OpVariable  %34  Input
 %37 = OpConstant  %16  8
-%2 = OpVariable  %15  Output
+%12 = OpVariable  %15  Output
 %38 = OpConstant  %18  16
 %39 = OpConstant  %14  32
 %40 = OpConstant  %21  64

Original file line number	Diff line number	Diff line change
`@@ -654,7 +654,7 @@ pub fn link(`
`654`	`654`
`655`	`655`	`{`
`656`	`656`	`let _timer = sess.timer("link_gather_all_interface_vars_from_uses");`
`657`		`- entry_interface::gather_all_interface_vars_from_uses(&mut output);`
	`657`	`+ entry_interface::gather_all_interface_vars_from_uses(&mut output, opts.preserve_bindings);`
`658`	`658`	`}`
`659`	`659`
`660`	`660`	`if opts.spirv_metadata == SpirvMetadata::NameVariables {`