[llvm] New "initialized" parameter attribute LangRef (PR #82564)

[Haopeng Liu via llvm-commits]

https://github.com/haopliu created https://github.com/llvm/llvm-project/pull/82564

None

>From 5b9a37179a09ab1671fa78b696b87b348ded8b16 Mon Sep 17 00:00:00 2001
From: Haopeng Liu <haopliu at google.com>
Date: Fri, 16 Feb 2024 00:57:31 +0000
Subject: [PATCH 1/2] add initialized attribute LangRef

---
 llvm/docs/LangRef.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index fd2e3aacd0169c..6f7a0fd3f7ba5a 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1589,6 +1589,23 @@ Currently, only the following parameter attributes are defined:
     ``readonly`` or a ``memory`` attribute that does not contain
     ``argmem: write``.
 
+``initialized((Lo1,Hi1),...)``
+    This attribute is a list of const ranges in ascending order with no
+    overlapping or continuous. It indicates that the function initializes the
+    memory through the pointer argument, [%p+LoN, %p+HiN), and there is no read
+    before initialization in the function. (even though it may read before
+    initializating the memory that the pointer points to).
+
+    The ``writable`` or ``dereferenceable`` attribute does not imply
+    ``initialized`` attribute, however the ``initialized`` argument does imply
+    ``writable`` and ``dereferenceable`` in the specified spaces.
+
+    The ``initialized`` attribute can combine with ``writeonly`` attribute, but
+    cannot be combined with ``readnone``, ``readonly`` or a memory attribute
+    that does not contain ``argmem: write``.
+
+    [TODO: unwind]
+
 ``dead_on_unwind``
     At a high level, this attribute indicates that the pointer argument is dead
     if the call unwinds, in the sense that the caller will not depend on the

>From 0be7b883bd97de1113a85bb0ca6ecf6875a6098e Mon Sep 17 00:00:00 2001
From: Haopeng Liu <haopliu at google.com>
Date: Thu, 22 Feb 2024 01:11:13 +0000
Subject: [PATCH 2/2] update initialized attr LangRef

---
 llvm/docs/LangRef.rst | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 6f7a0fd3f7ba5a..b140fef11ecbed 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1592,10 +1592,19 @@ Currently, only the following parameter attributes are defined:
 ``initialized((Lo1,Hi1),...)``
     This attribute is a list of const ranges in ascending order with no
     overlapping or continuous. It indicates that the function initializes the
-    memory through the pointer argument, [%p+LoN, %p+HiN), and there is no read
-    before initialization in the function. (even though it may read before
-    initializating the memory that the pointer points to).
-
+    memory through the pointer argument, [%p+LoN, %p+HiN): there are no reads,
+    no special uses (such as volatile access, untrackable capture, arithmetic
+    operation), and no instructions that may throw an exception before the
+    initialization in the function.
+
+    Similarly to ``writeonly`` or ``readonly``, this attribute implies that
+    the function initializes and does not read before initialization through
+    this pointer argument, even though it may read the memory before
+    initialization that the pointer points to, such as through other arguments.
+
+    Note that as there are no instructions that may throw an exception before
+    initialization, this attribute is still validated even if the call unwinds.
+   
     The ``writable`` or ``dereferenceable`` attribute does not imply
     ``initialized`` attribute, however the ``initialized`` argument does imply
     ``writable`` and ``dereferenceable`` in the specified spaces.
@@ -1604,8 +1613,6 @@ Currently, only the following parameter attributes are defined:
     cannot be combined with ``readnone``, ``readonly`` or a memory attribute
     that does not contain ``argmem: write``.
 
-    [TODO: unwind]
-
 ``dead_on_unwind``
     At a high level, this attribute indicates that the pointer argument is dead
     if the call unwinds, in the sense that the caller will not depend on the