[BuildLibCalls] Infer attributes for posix_memalign

[tommat01]

Handle the posix_memalign libcall in llvm::inferNonMandatoryLibFuncAttrs to annotate it with some properties about it.

The missing capture information caused Attributor to treat an alloca passed to posix_memalign as escaped, preventing noalias inference. Fixing that only required adding capture(none) to the first argument, but it seemed sensible to add the other properties while we're here.

[llvmorg-github-actions]

@llvm/pr-subscribers-llvm-transforms

Author: Tomas Matheson (tommat01)

Changes

Handle the posix_memalign libcall in llvm::inferNonMandatoryLibFuncAttrs to annotate it with some properties about it.

The missing capture information caused Attributor to treat an alloca passed to posix_memalign as escaped, preventing noalias inference. Fixing that only required adding capture(none) to the first argument, but it seemed sensible to add the other properties while we're here.

---

Full diff: https://github.com/llvm/llvm-project/pull/218681.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Utils/BuildLibCalls.cpp (+8)
• (modified) llvm/test/Transforms/InferFunctionAttrs/annotate.ll (+2-1)

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 0afcc9df40070..fd5ebc1c7d37a 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 |= setOnlyAccessesInaccessibleMemOrArgMemOrErrnoMem(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..d0c29faee8257 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) [[INACCESSIBLEMEMORARGMEMORERRNOMEMONLY_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 [[INACCESSIBLEMEMORARGMEMORERRNOMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] = { mustprogress nofree nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite, errnomem: write) }
 ; 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 }

[efriedma-quic]

LGTM

[antoniofrighetto]

LGTM