[llvm] [AArch64] Increase scatter overhead on Neoverse-V2 (PR #101296)
Madhur Amilkanthwar via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 31 08:38:41 PDT 2024
https://github.com/madhur13490 updated https://github.com/llvm/llvm-project/pull/101296
>From 5bc19b3d59dded4756d2cd18d22c6cd727217b37 Mon Sep 17 00:00:00 2001
From: Madhur Amilkanthwar <madhura at nvidia.com>
Date: Thu, 25 Jul 2024 18:30:21 +0530
Subject: [PATCH] [AArch64] Increase scatter overhead on Neoverse-V2
This patch increases scatter overhead on Neoverse-V2 to 13.
This benefits s128 kernel from TSVC_2 test suite.
SPEC 17, RAJAPerf, Sptter are unaffected with this patch.
---
.../AArch64/AArch64TargetTransformInfo.cpp | 22 +++++++++++++++++--
.../LoopVectorize/AArch64/scatter-cost.ll | 8 +++++++
2 files changed, 28 insertions(+), 2 deletions(-)
create mode 100644 llvm/test/Transforms/LoopVectorize/AArch64/scatter-cost.ll
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 79c0e45e3aa5b..d8c6416849cc5 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -3389,8 +3389,26 @@ AArch64TTIImpl::getMaskedMemoryOpCost(unsigned Opcode, Type *Src,
return LT.first;
}
-static unsigned getSVEGatherScatterOverhead(unsigned Opcode) {
+static unsigned getSVEGatherScatterOverhead(unsigned Opcode, AArch64Subtarget::ARMProcFamilyEnum ProcFamily) {
+ assert((Opcode == Instruction::Load || Opcode == Instruction::Store) &&
+ "Should be called on only load or stores.");
return Opcode == Instruction::Load ? SVEGatherOverhead : SVEScatterOverhead;
+ unsigned Cost = 1;
+ switch(Opcode) {
+ case Instruction::Load:
+ Cost = SVEGatherOverhead;
+ break;
+ case Instruction::Store:
+ if (ProcFamily == AArch64Subtarget::NeoverseV2) {
+ Cost = 13;
+ } else {
+ Cost = SVEScatterOverhead;
+ }
+ break;
+ default:
+ llvm_unreachable("Shouldn't have reached here");
+ }
+ return Cost;
}
InstructionCost AArch64TTIImpl::getGatherScatterOpCost(
@@ -3424,7 +3442,7 @@ InstructionCost AArch64TTIImpl::getGatherScatterOpCost(
// Add on an overhead cost for using gathers/scatters.
// TODO: At the moment this is applied unilaterally for all CPUs, but at some
// point we may want a per-CPU overhead.
- MemOpCost *= getSVEGatherScatterOverhead(Opcode);
+ MemOpCost *= getSVEGatherScatterOverhead(Opcode, ST->getProcFamily());
return LT.first * MemOpCost * getMaxNumElements(LegalVF);
}
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scatter-cost.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scatter-cost.ll
new file mode 100644
index 0000000000000..8bdae00411a1f
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scatter-cost.ll
@@ -0,0 +1,8 @@
+; RUN: opt -mtriple aarch64 -mcpu=neoverse-v2 -passes="print<cost-model>" -disable-output | FileCheck %s
+; CHECK: Cost Model: Found an estimated cost of 52 for instruction: call void @llvm.masked.scatter.nxv4f32
+
+define void @masked_scatter_nxv8f32_i64(<vscale x 4 x float> %data, <vscale x 4 x ptr> %b, <vscale x 4 x i64> %V) #0 {
+ call void @llvm.masked.scatter.nxv4f32.nxv4p0(<vscale x 4 x float> %data, <vscale x 4 x ptr> %b, i32 4, <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i64 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer))
+ ret void
+}
+
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