[llvm] RuntimeLibcalls: Add malloc and free entries (PR #167081)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/167081

>From 89e79eac508bb69af2ad10a684de1e56b467e3a0 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 7 Nov 2025 17:19:28 -0800
Subject: [PATCH] RuntimeLibcalls: Add malloc and free entries

Calloc was already here, but not the others. Also add
manual type information.
---
 llvm/include/llvm/IR/RuntimeLibcalls.td       |  5 ++
 llvm/lib/IR/RuntimeLibcalls.cpp               | 75 +++++++++++++++++++
 .../Util/DeclareRuntimeLibcalls/basic.ll      |  9 +++
 3 files changed, 89 insertions(+)

diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td b/llvm/include/llvm/IR/RuntimeLibcalls.td
index 11e6127e0741d..5a66b23051b2f 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -382,7 +382,9 @@ def MEMMOVE : RuntimeLibcall;
 def MEMMOVE_CHK : RuntimeLibcall;
 def MEMSET : RuntimeLibcall;
 def MEMSET_CHK : RuntimeLibcall;
+def MALLOC : RuntimeLibcall;
 def CALLOC : RuntimeLibcall;
+def FREE : RuntimeLibcall;
 def BZERO : RuntimeLibcall;
 def STRLEN : RuntimeLibcall;
 
@@ -1101,8 +1103,11 @@ def __memcpy_chk : RuntimeLibcallImpl<MEMCPY_CHK>;
 def __memmove_chk : RuntimeLibcallImpl<MEMMOVE_CHK>;
 def __memset_chk : RuntimeLibcallImpl<MEMSET_CHK>;
 
+def malloc : RuntimeLibcallImpl<MALLOC>;
+
 // DSEPass can emit calloc if it finds a pair of malloc/memset
 def calloc : RuntimeLibcallImpl<CALLOC>;
+def free : RuntimeLibcallImpl<FREE>;
 
 } // End let IsDefault = true
 
diff --git a/llvm/lib/IR/RuntimeLibcalls.cpp b/llvm/lib/IR/RuntimeLibcalls.cpp
index cbe7a7b9f77f4..a5f842a5fb520 100644
--- a/llvm/lib/IR/RuntimeLibcalls.cpp
+++ b/llvm/lib/IR/RuntimeLibcalls.cpp
@@ -130,13 +130,23 @@ bool RuntimeLibcallsInfo::darwinHasExp10(const Triple &TT) {
   }
 }
 
+/// TODO: There is really no guarantee that sizeof(size_t) is equal to the index
+/// size of the default address space. This matches TargetLibraryInfo and should
+/// be kept in sync.
+static IntegerType *getSizeTType(LLVMContext &Ctx, const DataLayout &DL) {
+  return DL.getIndexType(Ctx, /*AddressSpace=*/0);
+}
+
 std::pair<FunctionType *, AttributeList>
 RuntimeLibcallsInfo::getFunctionTy(LLVMContext &Ctx, const Triple &TT,
                                    const DataLayout &DL,
                                    RTLIB::LibcallImpl LibcallImpl) const {
+  // TODO: NoCallback probably unsafe in general
   static constexpr Attribute::AttrKind CommonFnAttrs[] = {
       Attribute::MustProgress, Attribute::NoCallback, Attribute::NoFree,
       Attribute::NoSync,       Attribute::NoUnwind,   Attribute::WillReturn};
+  static constexpr Attribute::AttrKind MemoryFnAttrs[] = {
+      Attribute::MustProgress, Attribute::NoUnwind, Attribute::WillReturn};
   static constexpr Attribute::AttrKind CommonPtrArgAttrs[] = {
       Attribute::NoAlias, Attribute::WriteOnly, Attribute::NonNull};
 
@@ -182,6 +192,71 @@ RuntimeLibcallsInfo::getFunctionTy(LLVMContext &Ctx, const Triple &TT,
 
     return {FunctionType::get(RetTy, {ScalarTy}, false), Attrs};
   }
+  case RTLIB::impl_malloc:
+  case RTLIB::impl_calloc: {
+    AttrBuilder FuncAttrBuilder(Ctx);
+    for (Attribute::AttrKind Attr : MemoryFnAttrs)
+      FuncAttrBuilder.addAttribute(Attr);
+    FuncAttrBuilder.addAttribute(Attribute::NoFree);
+
+    AllocFnKind AllocKind = AllocFnKind::Alloc;
+    if (LibcallImpl == RTLIB::impl_malloc)
+      AllocKind |= AllocFnKind::Uninitialized;
+
+    // TODO: Set memory attribute
+    FuncAttrBuilder.addAllocKindAttr(AllocKind);
+    FuncAttrBuilder.addAttribute("alloc-family", "malloc");
+    FuncAttrBuilder.addAllocSizeAttr(0, LibcallImpl == RTLIB::impl_malloc
+                                            ? std::nullopt
+                                            : std::make_optional(1));
+
+    AttributeList Attrs;
+    Attrs = Attrs.addFnAttributes(Ctx, FuncAttrBuilder);
+
+    {
+      AttrBuilder ArgAttrBuilder(Ctx);
+      for (Attribute::AttrKind AK : CommonPtrArgAttrs)
+        ArgAttrBuilder.addAttribute(AK);
+
+      Attrs = Attrs.addRetAttribute(Ctx, Attribute::NoUndef);
+      Attrs = Attrs.addRetAttribute(Ctx, Attribute::NoAlias);
+      Attrs = Attrs.addParamAttribute(Ctx, 0, Attribute::NoUndef);
+      if (LibcallImpl == RTLIB::impl_calloc)
+        Attrs = Attrs.addParamAttribute(Ctx, 1, Attribute::NoUndef);
+    }
+
+    IntegerType *SizeT = getSizeTType(Ctx, DL);
+    PointerType *PtrTy = PointerType::get(Ctx, 0);
+    SmallVector<Type *, 2> ArgTys = {SizeT};
+    if (LibcallImpl == RTLIB::impl_calloc)
+      ArgTys.push_back(SizeT);
+
+    return {FunctionType::get(PtrTy, ArgTys, false), Attrs};
+  }
+  case RTLIB::impl_free: {
+    // TODO: Set memory attribute
+    AttrBuilder FuncAttrBuilder(Ctx);
+    for (Attribute::AttrKind Attr : MemoryFnAttrs)
+      FuncAttrBuilder.addAttribute(Attr);
+
+    FuncAttrBuilder.addAllocKindAttr(AllocFnKind::Free);
+    FuncAttrBuilder.addAttribute("alloc-family", "malloc");
+
+    AttributeList Attrs;
+    Attrs = Attrs.addFnAttributes(Ctx, FuncAttrBuilder);
+
+    {
+      AttrBuilder ArgAttrBuilder(Ctx);
+      ArgAttrBuilder.addAttribute(Attribute::NoUndef);
+      ArgAttrBuilder.addAttribute(Attribute::AllocatedPointer);
+      ArgAttrBuilder.addCapturesAttr(CaptureInfo::none());
+      Attrs = Attrs.addParamAttributes(Ctx, 0, ArgAttrBuilder);
+    }
+
+    return {FunctionType::get(Type::getVoidTy(Ctx), {PointerType::get(Ctx, 0)},
+                              false),
+            Attrs};
+  }
   case RTLIB::impl_sqrtf:
   case RTLIB::impl_sqrt: {
     AttrBuilder FuncAttrBuilder(Ctx);
diff --git a/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/basic.ll b/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/basic.ll
index db0cc24c287bc..f1a039dc033ac 100644
--- a/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/basic.ll
+++ b/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/basic.ll
@@ -20,10 +20,16 @@ define float @sinf(float %x) {
 
 ; CHECK: declare void @acosf(...)
 
+; CHECK: declare noalias noundef ptr @calloc(i64 noundef, i64 noundef) [[CALLOC_ATTRS:#[0-9]+]]
+
 ; CHECK: declare void @fdim(...)
 ; CHECK: declare void @fdimf(...)
 ; CHECK: declare void @fdiml(...)
 
+; CHECK: declare void @free(ptr allocptr noundef captures(none)) [[FREE_ATTRS:#[0-9]+]]
+
+; CHECK: declare noalias noundef ptr @malloc(i64 noundef) [[MALLOC_ATTRS:#[0-9]+]]
+
 ; CHECK: declare void @nan(...)
 ; CHECK: declare void @nanf(...)
 ; CHECK: declare void @nanl(...)
@@ -58,3 +64,6 @@ define float @sinf(float %x) {
 
 ; CHECK: declare void @truncl(...)
 
+; CHECK: attributes [[CALLOC_ATTRS]] = { mustprogress nofree nounwind willreturn allockind("alloc") allocsize(0,1) "alloc-family"="malloc" }
+; CHECK: attributes [[FREE_ATTRS]] = { mustprogress nounwind willreturn allockind("free") "alloc-family"="malloc" }
+; CHECK: attributes [[MALLOC_ATTRS]] = { mustprogress nofree nounwind willreturn allockind("alloc,uninitialized") allocsize(0) "alloc-family"="malloc" }