[llvm] [BuildLibCalls] Infer attributes for posix_memalign (#218681) (PR #226943)

[Tomas Matheson via llvm-commits]

https://github.com/tommat01 created https://github.com/llvm/llvm-project/pull/226943

https://github.com/llvm/llvm-project/pull/218681 was merged to the wrong branch. Merge to main.

>From 54906367d541146690391aa5abdd17dfd770edff Mon Sep 17 00:00:00 2001
From: Tomas Matheson <Tomas.Matheson at arm.com>
Date: Fri, 25 Sep 2026 12:02:58 +0100
Subject: [PATCH] [BuildLibCalls] Infer attributes for posix_memalign (#218681)

Handle posix_memalign in inferNonMandatoryLibFuncAttrs.
---
 llvm/lib/Transforms/Utils/BuildLibCalls.cpp         | 8 ++++++++
 llvm/test/Transforms/InferFunctionAttrs/annotate.ll | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index fa61a18de15de..50813fb009247 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -534,6 +534,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
+  case LibFunc_posix_memalign:
+    Changed |= setRetAndArgsNoUndef(F);
+    Changed |= setDoesNotThrow(F);
+    Changed |= setWillReturn(F);
+    Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
+    Changed |= setDoesNotCapture(F, 0);
+    Changed |= setOnlyWritesMemory(F, 0);
+    break;
   case LibFunc_aligned_alloc:
     Changed |= setAlignedAllocParam(F, 0);
     Changed |= setAllocSize(F, 1, std::nullopt);
diff --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
index 44b76640cf97f..d9ebc1e210dc5 100644
--- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
@@ -817,7 +817,7 @@ declare void @perror(ptr)
 ; CHECK: declare noalias noundef ptr @popen(ptr noundef readonly captures(none), ptr noundef readonly captures(none)) [[NOFREE_NOUNWIND]]
 declare ptr @popen(ptr, ptr)
 
-; CHECK: declare i32 @posix_memalign(ptr, i64, i64) [[NOFREE]]
+; CHECK: declare noundef i32 @posix_memalign(ptr noundef writeonly captures(none), i64 noundef, i64 noundef) [[INACCESSIBLEMEMORARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
 declare i32 @posix_memalign(ptr, i64, i64)
 
 ; CHECK: declare double @pow(double, double) [[ERRNOMEMONLY_NOFREE_NOSYNC_NOUNWIND_WILLRETURN]]
@@ -1250,6 +1250,7 @@ declare void @memset_pattern16(ptr, ptr, i64)
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMORERRNOMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_REALLOC_ALLOCSIZE1_FAMILY_MALLOC]] = { mustprogress nounwind willreturn allockind("realloc") allocsize(1) memory(argmem: readwrite, inaccessiblemem: readwrite, errnomem: write) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMORERRNOMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_REALLOC_ALLOCSIZE12_FAMILY_MALLOC]] = { mustprogress nounwind willreturn allockind("realloc") allocsize(1,2) memory(argmem: readwrite, inaccessiblemem: readwrite, errnomem: write) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMORERRNOMEMONLY_NOFREE_NOUNWIND_WILLRETURN_FAMILY_MALLOC]] = { mustprogress nofree nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite, errnomem: write) "alloc-family"="malloc" }
+; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] = { mustprogress nofree nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite) }
 ; CHECK-DAG: attributes [[NOFREE_COLD_NORETURN_NOUNWIND]] = { cold nofree noreturn nounwind }
 ; CHECK-DAG: attributes [[NOFREE_COLD_NORETURN]] = { cold nofree noreturn }
 ; CHECK-DAG: attributes [[COLD_NORETURN]] = { cold noreturn }