From 6f29ad5974e2f1190fa05e901b50a6c6433a72d8 Mon Sep 17 00:00:00 2001 From: Simon Pilgrim Date: Wed, 1 Oct 2025 12:11:57 +0100 Subject: [PATCH] [DAG] Add ComputeNumSignBits(FREEZE(X)) handling If X is known never under/poison then skip the freeze and return ComputeNumSignBits(X) --- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 5 +++++ llvm/test/CodeGen/AArch64/freeze.ll | 6 ------ 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 8fc7eabf90ea8..95f53fe0bfdba 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -4762,6 +4762,11 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts, case ISD::AssertZext: Tmp = cast(Op.getOperand(1))->getVT().getSizeInBits(); return VTBits-Tmp; + case ISD::FREEZE: + if (isGuaranteedNotToBeUndefOrPoison(Op.getOperand(0), DemandedElts, + /*PoisonOnly=*/false)) + return ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1); + break; case ISD::MERGE_VALUES: return ComputeNumSignBits(Op.getOperand(Op.getResNo()), DemandedElts, Depth + 1); diff --git a/llvm/test/CodeGen/AArch64/freeze.ll b/llvm/test/CodeGen/AArch64/freeze.ll index fae3bbe2dcfba..fb909fec90434 100644 --- a/llvm/test/CodeGen/AArch64/freeze.ll +++ b/llvm/test/CodeGen/AArch64/freeze.ll @@ -466,15 +466,12 @@ define <8 x i16> @freeze_urhadd(<8 x i16> %a0, <8 x i16> %a1) { ret <8 x i16> %masked } -; TODO: Unnecessary sext_inreg define <8 x i16> @freeze_shadd(<8 x i8> %a0, <8 x i16> %a1) { ; CHECK-LABEL: freeze_shadd: ; CHECK: // %bb.0: ; CHECK-NEXT: sshll v0.8h, v0.8b, #0 ; CHECK-NEXT: sshr v1.8h, v1.8h, #8 ; CHECK-NEXT: shadd v0.8h, v0.8h, v1.8h -; CHECK-NEXT: shl v0.8h, v0.8h, #8 -; CHECK-NEXT: sshr v0.8h, v0.8h, #8 ; CHECK-NEXT: ret %x0 = sext <8 x i8> %a0 to <8 x i16> %x1 = ashr <8 x i16> %a1, splat (i16 8) @@ -485,15 +482,12 @@ define <8 x i16> @freeze_shadd(<8 x i8> %a0, <8 x i16> %a1) { ret <8 x i16> %sext } -; TODO: Unnecessary sext_inreg define <8 x i16> @freeze_srhadd(<8 x i8> %a0, <8 x i16> %a1) { ; CHECK-LABEL: freeze_srhadd: ; CHECK: // %bb.0: ; CHECK-NEXT: sshll v0.8h, v0.8b, #0 ; CHECK-NEXT: sshr v1.8h, v1.8h, #8 ; CHECK-NEXT: srhadd v0.8h, v0.8h, v1.8h -; CHECK-NEXT: shl v0.8h, v0.8h, #8 -; CHECK-NEXT: sshr v0.8h, v0.8h, #8 ; CHECK-NEXT: ret %x0 = sext <8 x i8> %a0 to <8 x i16> %x1 = ashr <8 x i16> %a1, splat (i16 8)