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AMDGPU: llvm.amdgcn.inverse.ballot needs to be convergent #155725

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Aug 28, 2025
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AMDGPU: llvm.amdgcn.inverse.ballot needs to be convergent #155725

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6 changes: 5 additions & 1 deletion llvm/include/llvm/IR/IntrinsicsAMDGPU.td
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Original file line number Diff line number Diff line change
Expand Up @@ -2434,9 +2434,13 @@ def int_amdgcn_ballot :
Intrinsic<[llvm_anyint_ty], [llvm_i1_ty],
[IntrNoMem, IntrConvergent, IntrWillReturn, IntrNoCallback, IntrNoFree]>;

// Inverse of ballot: return the bit corresponding to the current lane from the
// given mask.
//
// This is only defined for dynamically uniform masks and therefore convergent.
def int_amdgcn_inverse_ballot :
Intrinsic<[llvm_i1_ty], [llvm_anyint_ty],
[IntrNoMem, IntrWillReturn, IntrNoCallback, IntrNoFree]>;
[IntrNoMem, IntrConvergent, IntrWillReturn, IntrNoCallback, IntrNoFree]>;

// Lowers to S_BITREPLICATE_B64_B32.
// The argument must be uniform; otherwise, the result is undefined.
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/AMDGPU/llvm.amdgcn.inverse.ballot.i32.ll
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Expand Up @@ -5,7 +5,7 @@
; RUN: not llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize64 -global-isel=1 < %s 2>&1 | FileCheck -check-prefix=GISEL-ERR %s
; RUN: not --crash llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize64 -global-isel=0 < %s 2>&1 | FileCheck -check-prefix=SDAG-ERR %s

; GISEL-ERR: LLVM ERROR: cannot select: {{.*}} = G_INTRINSIC intrinsic(@llvm.amdgcn.inverse.ballot)
; GISEL-ERR: LLVM ERROR: cannot select: {{.*}} = G_INTRINSIC_CONVERGENT intrinsic(@llvm.amdgcn.inverse.ballot)
; SDAG-ERR: LLVM ERROR: Cannot select: intrinsic %llvm.amdgcn.inverse.ballot

declare i1 @llvm.amdgcn.inverse.ballot(i32)
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