[llvm] df34428 - [IR] Relax convergence requirements on call (#135794)
via llvm-commits
llvm-commits at lists.llvm.org
Fri May 2 01:18:01 PDT 2025
Author: Nathan Gauër
Date: 2025-05-02T08:17:58Z
New Revision: df344285e260109e016e28a14e663f376d8e903c
URL: https://github.com/llvm/llvm-project/commit/df344285e260109e016e28a14e663f376d8e903c
DIFF: https://github.com/llvm/llvm-project/commit/df344285e260109e016e28a14e663f376d8e903c.diff
LOG: [IR] Relax convergence requirements on call (#135794)
Before this commit, having a convergence token on a non-convergent call
was considered to be an error.
This commit relaxes this requirement and allows convergence tokens to be
present on non-convergent calls.
When such token is present, they have no effect as the underlying call
is non-convergent.
This allows passes like DCE to strip `convergent` attribute from
functions for which all convergent operations have been stripped. When
this happens, a convergence token can still exist in the call-site,
causing the verifier to complain.
Alternatives have been considered in #134863 and #134844.
Added:
llvm/test/Transforms/ADCE/convergence.ll
llvm/test/Transforms/BDCE/convergence.ll
Modified:
llvm/include/llvm/IR/GenericConvergenceVerifierImpl.h
llvm/test/Assembler/convergence-control.ll
llvm/test/Transforms/FunctionAttrs/convergent.ll
llvm/test/Verifier/convergencectrl-invalid.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/GenericConvergenceVerifierImpl.h b/llvm/include/llvm/IR/GenericConvergenceVerifierImpl.h
index e076ac4a14162..ddcce17b77c8b 100644
--- a/llvm/include/llvm/IR/GenericConvergenceVerifierImpl.h
+++ b/llvm/include/llvm/IR/GenericConvergenceVerifierImpl.h
@@ -102,9 +102,6 @@ void GenericConvergenceVerifier<ContextT>::visit(const InstructionT &I) {
SeenFirstConvOp = true;
if (TokenDef || ConvOp != CONV_NONE) {
- Check(isConvergent(I),
- "Convergence control token can only be used in a convergent call.",
- {Context.print(&I)});
Check(ConvergenceKind != UncontrolledConvergence,
"Cannot mix controlled and uncontrolled convergence in the same "
"function.",
diff --git a/llvm/test/Assembler/convergence-control.ll b/llvm/test/Assembler/convergence-control.ll
index f32f4a9f53707..c7dd04cf5c25b 100644
--- a/llvm/test/Assembler/convergence-control.ll
+++ b/llvm/test/Assembler/convergence-control.ll
@@ -24,6 +24,13 @@ define void @mixed2() {
ret void
}
+; convergence control token can be used on non-convergent calls,
+; but it has no effect.
+define void @mixed3() {
+ %t05_tok1 = call token @llvm.experimental.convergence.anchor()
+ call void @g() [ "convergencectrl"(token %t05_tok1) ]
+ ret void
+}
define void @region_nesting1(i1 %arg) convergent {
A:
diff --git a/llvm/test/Transforms/ADCE/convergence.ll b/llvm/test/Transforms/ADCE/convergence.ll
new file mode 100644
index 0000000000000..01a205ebda148
--- /dev/null
+++ b/llvm/test/Transforms/ADCE/convergence.ll
@@ -0,0 +1,93 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt %s -passes=adce -S | FileCheck %s
+
+define i32 @foo(i32 %a) #0 {
+; CHECK-LABEL: define i32 @foo(
+; CHECK-SAME: i32 [[A:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret i32 [[A]]
+;
+entry:
+ %tk = call token @llvm.experimental.convergence.entry()
+ ret i32 %a
+}
+
+define void @bar() #0 {
+; CHECK-LABEL: define void @bar(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk = call token @llvm.experimental.convergence.anchor()
+ ret void
+}
+
+define void @baz() #0 {
+; CHECK-LABEL: define void @baz(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: br label %[[HEADER:.*]]
+; CHECK: [[HEADER]]:
+; CHECK-NEXT: br i1 true, label %[[BODY:.*]], label %[[EXIT:.*]]
+; CHECK: [[BODY]]:
+; CHECK-NEXT: br label %[[HEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.entry()
+ br label %header
+
+header:
+ %tk1 = call token @llvm.experimental.convergence.loop() [ "convergencectrl"(token %tk0) ]
+ br i1 true, label %body, label %exit
+
+body:
+ br label %header
+
+exit:
+ ret void
+}
+
+define void @indirect_inner() #0 {
+; CHECK-LABEL: define void @indirect_inner(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.entry()
+ ret void
+}
+
+define void @indirect() #0 {
+; CHECK-LABEL: define void @indirect(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[TK0:%.*]] = call token @llvm.experimental.convergence.entry()
+; CHECK-NEXT: [[VAR:%.*]] = alloca ptr, align 8
+; CHECK-NEXT: store ptr @indirect_inner, ptr [[VAR]], align 8
+; CHECK-NEXT: [[PTR:%.*]] = load ptr, ptr [[VAR]], align 8
+; CHECK-NEXT: call void [[PTR]]() #[[ATTR0]] [ "convergencectrl"(token [[TK0]]) ]
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.entry()
+ %var = alloca ptr, align 8
+ store ptr @indirect_inner, ptr %var, align 8
+ %ptr = load ptr, ptr %var, align 8
+ call void %ptr() convergent [ "convergencectrl"(token %tk0) ]
+ ret void
+}
+
+declare token @llvm.experimental.convergence.entry() #1
+declare token @llvm.experimental.convergence.anchor() #1
+declare token @llvm.experimental.convergence.loop() #1
+
+attributes #0 = { convergent }
+attributes #1 = { convergent nocallback nofree nosync nounwind willreturn memory(none) }
+;.
+; CHECK: attributes #[[ATTR0]] = { convergent }
+; CHECK: attributes #[[ATTR1:[0-9]+]] = { convergent nocallback nofree nosync nounwind willreturn memory(none) }
+;.
diff --git a/llvm/test/Transforms/BDCE/convergence.ll b/llvm/test/Transforms/BDCE/convergence.ll
new file mode 100644
index 0000000000000..5bebe37acc845
--- /dev/null
+++ b/llvm/test/Transforms/BDCE/convergence.ll
@@ -0,0 +1,62 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt %s -passes=bdce -S | FileCheck %s
+
+define i32 @foo(i32 %a) #0 {
+; CHECK-LABEL: define i32 @foo(
+; CHECK-SAME: i32 [[A:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret i32 [[A]]
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.entry()
+ ret i32 %a
+}
+
+define void @bar() #0 {
+; CHECK-LABEL: define void @bar(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.anchor()
+ ret void
+}
+
+define void @baz() #0 {
+; CHECK-LABEL: define void @baz(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: br label %[[HEADER:.*]]
+; CHECK: [[HEADER]]:
+; CHECK-NEXT: br i1 true, label %[[BODY:.*]], label %[[EXIT:.*]]
+; CHECK: [[BODY]]:
+; CHECK-NEXT: br label %[[HEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: ret void
+;
+entry:
+ %tk0 = call token @llvm.experimental.convergence.entry()
+ br label %header
+
+header:
+ %tk1 = call token @llvm.experimental.convergence.loop() [ "convergencectrl"(token %tk0) ]
+ br i1 true, label %body, label %exit
+
+body:
+ br label %header
+
+exit:
+ ret void
+}
+
+declare token @llvm.experimental.convergence.entry() #1
+declare token @llvm.experimental.convergence.anchor() #1
+declare token @llvm.experimental.convergence.loop() #1
+
+attributes #0 = { convergent }
+attributes #1 = { convergent nocallback nofree nosync nounwind willreturn memory(none) }
+;.
+; CHECK: attributes #[[ATTR0]] = { convergent }
+; CHECK: attributes #[[ATTR1:[0-9]+]] = { convergent nocallback nofree nosync nounwind willreturn memory(none) }
+;.
diff --git a/llvm/test/Transforms/FunctionAttrs/convergent.ll b/llvm/test/Transforms/FunctionAttrs/convergent.ll
index fe8029d39d924..49c357bd6bc86 100644
--- a/llvm/test/Transforms/FunctionAttrs/convergent.ll
+++ b/llvm/test/Transforms/FunctionAttrs/convergent.ll
@@ -1,4 +1,4 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes --check-globals
; RUN: opt -passes=function-attrs -S < %s | FileCheck %s
define i32 @nonleaf() convergent {
@@ -129,3 +129,43 @@ define i32 @noopt_friend() convergent {
%a = call i32 @noopt()
ret i32 0
}
+
+
+; A function which is stripped of its convergent attribute, even
+; if used in a controlled convergence call.
+; This should be OK.
+define i32 @leaf_noconvergent_used() convergent {
+; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; CHECK-LABEL: define {{[^@]+}}@leaf_noconvergent_used
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT: ret i32 0
+;
+ ret i32 0
+}
+
+define i32 @nonleaf_convergent() convergent {
+; CHECK: Function Attrs: convergent mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; CHECK-LABEL: define {{[^@]+}}@nonleaf_convergent
+; CHECK-SAME: () #[[ATTR7:[0-9]+]] {
+; CHECK-NEXT: [[TMP1:%.*]] = call token @llvm.experimental.convergence.entry()
+; CHECK-NEXT: [[TMP2:%.*]] = call i32 @leaf_noconvergent_used() [ "convergencectrl"(token [[TMP1]]) ]
+; CHECK-NEXT: ret i32 0
+;
+ %1 = call token @llvm.experimental.convergence.entry()
+ %2 = call i32 @leaf_noconvergent_used() [ "convergencectrl"(token %1) ]
+ ret i32 0
+}
+
+
+declare token @llvm.experimental.convergence.entry() #1
+;.
+; CHECK: attributes #[[ATTR0]] = { mustprogress nofree norecurse nosync nounwind willreturn memory(none) }
+; CHECK: attributes #[[ATTR1]] = { convergent }
+; CHECK: attributes #[[ATTR2]] = { norecurse }
+; CHECK: attributes #[[ATTR3:[0-9]+]] = { convergent nocallback nounwind }
+; CHECK: attributes #[[ATTR4]] = { convergent norecurse nounwind }
+; CHECK: attributes #[[ATTR5]] = { nofree nosync nounwind memory(none) }
+; CHECK: attributes #[[ATTR6]] = { convergent noinline optnone }
+; CHECK: attributes #[[ATTR7]] = { convergent mustprogress nofree norecurse nosync nounwind willreturn memory(none) }
+; CHECK: attributes #[[ATTR8:[0-9]+]] = { convergent nocallback nofree nosync nounwind willreturn memory(none) }
+;.
diff --git a/llvm/test/Verifier/convergencectrl-invalid.ll b/llvm/test/Verifier/convergencectrl-invalid.ll
index e1fffcd1c6033..907c3464ffce9 100644
--- a/llvm/test/Verifier/convergencectrl-invalid.ll
+++ b/llvm/test/Verifier/convergencectrl-invalid.ll
@@ -20,14 +20,6 @@ define void @wrong_token() {
ret void
}
-; CHECK: Convergence control token can only be used in a convergent call.
-; CHECK-NEXT call void @g(){{.*}}%t05_tok1
-define void @missing.attribute() {
- %t05_tok1 = call token @llvm.experimental.convergence.anchor()
- call void @g() [ "convergencectrl"(token %t05_tok1) ]
- ret void
-}
-
; CHECK: The 'convergencectrl' bundle requires exactly one token use.
; CHECK-NEXT: call void @g()
define void @multiple_tokens() {
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