[llvm] [VectorUtils] Add helper to get list of metadata to propagate (NFC). (PR #135003)

[Florian Hahn via llvm-commits]

https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/135003

>From 32354bbce962d936f0d9a7a02a3cd072d60796b4 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 9 Apr 2025 13:44:53 +0100
Subject: [PATCH 1/3] [VectorUtils] Add helper to get list of metadata to
 propagate (NFC).

Split off the logic to filter out metadata that should not be propagated
to a helper that populates a list with metadata kinds that should be
preserved.

The current version just uses is_contained on an array to check if a
metadata kind is supported. Given that most instructions will only have
a small number of metadata kinds to start with, this shouldn't be worse
than iterating over all kinds once and querying the instruction for
individual metadata kinds, which involves quite a bit of indirection.

I plan ot use this utility in a follow-up patch in other places as well.
---
 llvm/lib/Analysis/VectorUtils.cpp | 37 +++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp
index 46f588f4c6705..1c0ea87990a3a 100644
--- a/llvm/lib/Analysis/VectorUtils.cpp
+++ b/llvm/lib/Analysis/VectorUtils.cpp
@@ -984,19 +984,38 @@ MDNode *llvm::intersectAccessGroups(const Instruction *Inst1,
   return MDNode::get(Ctx, Intersection);
 }
 
+/// Add metadata from \p Inst to \p Metadata, if it can be preserved after
+/// vectorization.
+static void getMetadataToPropagate(
+    Instruction *Inst,
+    SmallVectorImpl<std::pair<unsigned, MDNode *>> &Metadata) {
+  Inst->getAllMetadataOtherThanDebugLoc(Metadata);
+  unsigned SupportedIDs[] = {
+      LLVMContext::MD_tbaa,         LLVMContext::MD_alias_scope,
+      LLVMContext::MD_noalias,      LLVMContext::MD_fpmath,
+      LLVMContext::MD_nontemporal,  LLVMContext::MD_invariant_load,
+      LLVMContext::MD_access_group, LLVMContext::MD_mmra};
+
+  // Remove any unsupported metadata kinds from Metadata.
+  for (unsigned Idx = 0; Idx != Metadata.size();) {
+    if (is_contained(SupportedIDs, Metadata[Idx].first))
+      Idx++;
+    else {
+      // Swap element to end and remove it.
+      std::swap(Metadata[Idx], Metadata.back());
+      Metadata.pop_back();
+    }
+  }
+}
+
 /// \returns \p I after propagating metadata from \p VL.
 Instruction *llvm::propagateMetadata(Instruction *Inst, ArrayRef<Value *> VL) {
   if (VL.empty())
     return Inst;
-  Instruction *I0 = cast<Instruction>(VL[0]);
-  SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
-  I0->getAllMetadataOtherThanDebugLoc(Metadata);
-
-  for (auto Kind : {LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
-                    LLVMContext::MD_noalias, LLVMContext::MD_fpmath,
-                    LLVMContext::MD_nontemporal, LLVMContext::MD_invariant_load,
-                    LLVMContext::MD_access_group, LLVMContext::MD_mmra}) {
-    MDNode *MD = I0->getMetadata(Kind);
+  SmallVector<std::pair<unsigned, MDNode *>> Metadata;
+  getMetadataToPropagate(cast<Instruction>(VL[0]), Metadata);
+
+  for (auto &[Kind, MD] : Metadata) {
     for (int J = 1, E = VL.size(); MD && J != E; ++J) {
       const Instruction *IJ = cast<Instruction>(VL[J]);
       MDNode *IMD = IJ->getMetadata(Kind);

>From f44451deea956f0df409853a7096487489fcedf1 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 9 Apr 2025 16:01:51 +0100
Subject: [PATCH 2/3] !fixup add {}

---
 llvm/lib/Analysis/VectorUtils.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp
index 1c0ea87990a3a..61acc99993d70 100644
--- a/llvm/lib/Analysis/VectorUtils.cpp
+++ b/llvm/lib/Analysis/VectorUtils.cpp
@@ -998,9 +998,9 @@ static void getMetadataToPropagate(
 
   // Remove any unsupported metadata kinds from Metadata.
   for (unsigned Idx = 0; Idx != Metadata.size();) {
-    if (is_contained(SupportedIDs, Metadata[Idx].first))
+    if (is_contained(SupportedIDs, Metadata[Idx].first)) {
       Idx++;
-    else {
+    } else {
       // Swap element to end and remove it.
       std::swap(Metadata[Idx], Metadata.back());
       Metadata.pop_back();

>From 2993d176d833c68723ee08383c57612971d4a2eb Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 9 Apr 2025 20:48:15 +0100
Subject: [PATCH 3/3] !fixup apply suggestions, thanks!

---
 llvm/lib/Analysis/VectorUtils.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp
index 61acc99993d70..2379093b512bb 100644
--- a/llvm/lib/Analysis/VectorUtils.cpp
+++ b/llvm/lib/Analysis/VectorUtils.cpp
@@ -990,7 +990,7 @@ static void getMetadataToPropagate(
     Instruction *Inst,
     SmallVectorImpl<std::pair<unsigned, MDNode *>> &Metadata) {
   Inst->getAllMetadataOtherThanDebugLoc(Metadata);
-  unsigned SupportedIDs[] = {
+  static const unsigned SupportedIDs[] = {
       LLVMContext::MD_tbaa,         LLVMContext::MD_alias_scope,
       LLVMContext::MD_noalias,      LLVMContext::MD_fpmath,
       LLVMContext::MD_nontemporal,  LLVMContext::MD_invariant_load,
@@ -999,7 +999,7 @@ static void getMetadataToPropagate(
   // Remove any unsupported metadata kinds from Metadata.
   for (unsigned Idx = 0; Idx != Metadata.size();) {
     if (is_contained(SupportedIDs, Metadata[Idx].first)) {
-      Idx++;
+      ++Idx;
     } else {
       // Swap element to end and remove it.
       std::swap(Metadata[Idx], Metadata.back());