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llvm-reduce: Avoid removing convergent with convergence tokens (#132946)
Check if the intrinsics are declared in the module as an overly conservative fix. Fixes #132695
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‎llvm/test/tools/llvm-reduce/remove-attributes-convergent-uncontrolled.ll

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
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; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=attributes --test FileCheck --test-arg --check-prefix=INTERESTING --test-arg %s --test-arg --input-file %s -o %t
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; RUN: FileCheck --check-prefixes=RESULT %s < %t
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; Test that convergent attributes are reduced if convergencectrl
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; bundles are not used
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; INTERESTING-LABEL: define float @convergent_intrinsic(
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; RESULT-LABEL: define float @convergent_intrinsic(float %x, float %y) {
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define float @convergent_intrinsic(float %x, float %y) #0 {
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%val = call float @llvm.amdgcn.readfirstlane.f32(float %x)
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ret float %val
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}
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; INTERESTING-LABEL: define float @convergent_func_no_convergent_intrinsics(
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; RESULT-LABEL: define float @convergent_func_no_convergent_intrinsics(float %x, float %y) {
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define float @convergent_func_no_convergent_intrinsics(float %x, float %y) #0 {
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%val = call float @extern.func(float %x, float %y)
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ret float %val
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}
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; RESULT-LABEL: declare float @convergent.extern.func(float, float){{$}}
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declare float @convergent.extern.func(float, float) #0
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declare float @extern.func(float, float)
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declare float @llvm.amdgcn.readfirstlane.f32(float) #1
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; RESULT: attributes #0 = { convergent nocallback nofree nounwind willreturn memory(none) }
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; RESULT-NOT: attributes
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attributes #0 = { convergent nounwind }
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attributes #1 = { convergent nocallback nofree nounwind willreturn memory(none) }

‎llvm/test/tools/llvm-reduce/remove-attributes-convergent.ll

Lines changed: 58 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,58 @@
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; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=attributes --test FileCheck --test-arg %s --test-arg --input-file %s -o %t
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; RUN: FileCheck --check-prefixes=CHECK,RESULT %s < %t
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; Test that invalid reductions aren't produced on convergent functions
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; which use convergencectrl bundles
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; CHECK-LABEL: define float @convergent_intrinsic(float %x, float %y)
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; RESULT-SAME: [[CONVERGENT_ONLY:#[0-9]+]] {
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define float @convergent_intrinsic(float %x, float %y) #0 {
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%entry.token = call token @llvm.experimental.convergence.entry()
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%val = call float @llvm.amdgcn.readfirstlane.f32(float %x) [ "convergencectrl"(token %entry.token) ]
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ret float %val
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}
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; CHECK-LABEL: define float @convergent_callsite(float %x, float %y)
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; RESULT-SAME: [[CONVERGENT_ONLY]] {
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; RESULT: call float @extern.func(float %x, float %y) [[CONVERGENT_ONLY]]
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define float @convergent_callsite(float %x, float %y) #0 {
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%entry.token = call token @llvm.experimental.convergence.entry()
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%val = call float @extern.func(float %x, float %y) #0 [ "convergencectrl"(token %entry.token) ]
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ret float %val
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}
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; CHECK-LABEL: define float @convergent_declaration(float %x, float %y)
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; RESULT-SAME: [[CONVERGENT_ONLY]] {
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define float @convergent_declaration(float %x, float %y) #0 {
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%entry.token = call token @llvm.experimental.convergence.entry()
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%val = call float @convergent.extern.func(float %x, float %y) [ "convergencectrl"(token %entry.token) ]
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ret float %val
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}
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; CHECK-LABEL: define float @convergent_func_no_convergent_intrinsics(float %x, float %y)
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; RESULT-SAME: [[CONVERGENT_ONLY]] {
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define float @convergent_func_no_convergent_intrinsics(float %x, float %y) #0 {
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%val = call float @extern.func(float %x, float %y)
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ret float %val
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}
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; CHECK-LABEL: define float @convergent_func_no_convergent_bundles(float %x, float %y)
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; RESULT-SAME: [[CONVERGENT_ONLY]] {
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define float @convergent_func_no_convergent_bundles(float %x, float %y) #0 {
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%entry.token = call token @llvm.experimental.convergence.entry()
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%val = call float @extern.func(float %x, float %y)
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ret float %val
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}
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; CHECK-LABEL: declare float @convergent.extern.func(float, float)
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; RESULT-SAME: [[CONVERGENT_ONLY]]{{$}}
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declare float @convergent.extern.func(float, float) #0
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declare float @extern.func(float, float)
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declare float @llvm.amdgcn.readfirstlane.f32(float) #1
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declare token @llvm.experimental.convergence.entry() #2
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; RESULT: attributes [[CONVERGENT_ONLY]] = { convergent }
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attributes #0 = { convergent nounwind }
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attributes #1 = { convergent nocallback nofree nounwind willreturn memory(none) }
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attributes #2 = { convergent nocallback nofree nosync nounwind willreturn memory(none) }

‎llvm/tools/llvm-reduce/deltas/ReduceAttributes.cpp

Lines changed: 25 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -44,9 +44,25 @@ namespace {
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class AttributeRemapper : public InstVisitor<AttributeRemapper> {
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Oracle &O;
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LLVMContext &Context;
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bool HasControlledConvergence = true;
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public:
49-
AttributeRemapper(Oracle &O, LLVMContext &C) : O(O), Context(C) {}
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AttributeRemapper(Oracle &O, Module &M) : O(O), Context(M.getContext()) {
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// Check if there are any convergence intrinsics used. We cannot remove the
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// convergent attribute if a function uses convergencectrl bundles. As a
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// simple filter, check if any of the intrinsics are used in the module.
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//
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// TODO: This could be done per-function. We should be eliminating
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// convergent if there are no convergent token uses in a function.
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HasControlledConvergence = any_of(
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ArrayRef<Intrinsic::ID>{Intrinsic::experimental_convergence_anchor,
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Intrinsic::experimental_convergence_entry,
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Intrinsic::experimental_convergence_loop},
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[&M](Intrinsic::ID ID) {
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return Intrinsic::getDeclarationIfExists(&M, ID);
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});
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}
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void visitModule(Module &M) {
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for (GlobalVariable &GV : M.globals())
@@ -132,6 +148,13 @@ class AttributeRemapper : public InstVisitor<AttributeRemapper> {
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AttrsToPreserve.addAttribute(A);
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continue;
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}
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// TODO: Could only remove this if there are no convergence tokens in
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// the function.
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if (Kind == Attribute::Convergent && HasControlledConvergence) {
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AttrsToPreserve.addAttribute(A);
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continue;
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}
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}
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137160
if (O.shouldKeep())
@@ -144,7 +167,7 @@ class AttributeRemapper : public InstVisitor<AttributeRemapper> {
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/// Removes out-of-chunk attributes from module.
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static void extractAttributesFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
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AttributeRemapper R(O, WorkItem.getContext());
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AttributeRemapper R(O, WorkItem.getModule());
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R.visit(WorkItem.getModule());
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}
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