[llvm] [AArch64][SME] Instcombine `llvm.aarch64.sme.in.streaming.mode()` (PR #147930)

[Benjamin Maxwell via llvm-commits]

https://github.com/MacDue created https://github.com/llvm/llvm-project/pull/147930

This can fold away in non-streaming-compatible functions.

>From c2a118d36cf976f18ff44a871e7a97185b06a115 Mon Sep 17 00:00:00 2001
From: Benjamin Maxwell <benjamin.maxwell at arm.com>
Date: Thu, 10 Jul 2025 09:57:09 +0000
Subject: [PATCH] [AArch64][SME] Instcombine
 `llvm.aarch64.sme.in.streaming.mode()`

This can fold away in non-streaming-compatible functions.
---
 .../AArch64/AArch64TargetTransformInfo.cpp    | 12 ++++++
 .../AArch64/aarch64-sme-in-streaming-mode.ll  | 38 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 llvm/test/Transforms/InstCombine/AArch64/aarch64-sme-in-streaming-mode.ll

diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index adc905384bf53..9e64e33818781 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -2723,6 +2723,16 @@ static std::optional<Instruction *> instCombineSVEUxt(InstCombiner &IC,
   return std::nullopt;
 }
 
+static std::optional<Instruction *>
+instCombineInStreamingMode(InstCombiner &IC, IntrinsicInst &II) {
+  SMEAttrs FnSMEAttrs(*II.getFunction());
+  if (FnSMEAttrs.hasStreamingCompatibleInterface())
+    return std::nullopt;
+  bool IsStreaming = FnSMEAttrs.hasStreamingInterfaceOrBody();
+  return IC.replaceInstUsesWith(
+      II, ConstantInt::getBool(II.getType(), IsStreaming));
+}
+
 std::optional<Instruction *>
 AArch64TTIImpl::instCombineIntrinsic(InstCombiner &IC,
                                      IntrinsicInst &II) const {
@@ -2828,6 +2838,8 @@ AArch64TTIImpl::instCombineIntrinsic(InstCombiner &IC,
     return instCombineSVEUxt(IC, II, 16);
   case Intrinsic::aarch64_sve_uxtw:
     return instCombineSVEUxt(IC, II, 32);
+  case Intrinsic::aarch64_sme_in_streaming_mode:
+    return instCombineInStreamingMode(IC, II);
   }
 
   return std::nullopt;
diff --git a/llvm/test/Transforms/InstCombine/AArch64/aarch64-sme-in-streaming-mode.ll b/llvm/test/Transforms/InstCombine/AArch64/aarch64-sme-in-streaming-mode.ll
new file mode 100644
index 0000000000000..c46f5c48429d3
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/AArch64/aarch64-sme-in-streaming-mode.ll
@@ -0,0 +1,38 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=instcombine -mtriple aarch64 -mattr=+sme -S -o - < %s | FileCheck %s
+
+define i1 @test_in_streaming_mode_streaming_compatible() "aarch64_pstate_sm_compatible" {
+; CHECK-LABEL: define i1 @test_in_streaming_mode_streaming_compatible(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[SM:%.*]] = tail call i1 @llvm.aarch64.sme.in.streaming.mode()
+; CHECK-NEXT:    ret i1 [[SM]]
+;
+  %sm = tail call i1 @llvm.aarch64.sme.in.streaming.mode()
+  ret i1 %sm
+}
+
+define i1 @test_in_streaming_mode_streaming() "aarch64_pstate_sm_enabled" {
+; CHECK-LABEL: define i1 @test_in_streaming_mode_streaming(
+; CHECK-SAME: ) #[[ATTR1:[0-9]+]] {
+; CHECK-NEXT:    ret i1 true
+;
+  %sm = tail call i1 @llvm.aarch64.sme.in.streaming.mode()
+  ret i1 %sm
+}
+define i1 @test_in_streaming_mode_streaming_body() "aarch64_pstate_sm_body" {
+; CHECK-LABEL: define i1 @test_in_streaming_mode_streaming_body(
+; CHECK-SAME: ) #[[ATTR2:[0-9]+]] {
+; CHECK-NEXT:    ret i1 true
+;
+  %sm = tail call i1 @llvm.aarch64.sme.in.streaming.mode()
+  ret i1 %sm
+}
+
+define i1 @test_in_streaming_mode_non_streaming() {
+; CHECK-LABEL: define i1 @test_in_streaming_mode_non_streaming(
+; CHECK-SAME: ) #[[ATTR3:[0-9]+]] {
+; CHECK-NEXT:    ret i1 false
+;
+  %sm = tail call i1 @llvm.aarch64.sme.in.streaming.mode()
+  ret i1 %sm
+}