From f6190ce920cc3e8937bc143bb4608a9f17480110 Mon Sep 17 00:00:00 2001
From: Kerry McLaughlin <kerry.mclaughlin@arm.com>
Date: Tue, 26 Nov 2024 09:37:51 +0000
Subject: [PATCH] Include SME attributes in the name mangling of types (#358)

This change extends the name mangling of types to include the SME
streaming and ZA interface. This will avoid naming conflicts which can
currently arise such as in the following example:

```
  void foo(void (*f)()) { f(); }
  void foo(void (*f)() __arm_streaming) { f(); }
```

Without this change, both functions 'foo' above will mangle to the same
name, despite the function pointers being different.
---
 main/acle.md | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/main/acle.md b/main/acle.md
index b038a5ee..1182f7bb 100644
--- a/main/acle.md
+++ b/main/acle.md
@@ -424,6 +424,7 @@ Armv8.4-A [[ARMARMv84]](#ARMARMv84). Support is added for the Dot Product intrin
 * Fixed SVE2.1 quadword gather load/scatter store intrinsics.
 * Removed unnecessary Zd argument from `svcvtnb_mf8[_f32_x2]_fpm`.
 * Fixed urls.
+* Changed name mangling of function types to include SME attributes.
 
 ### References
 
@@ -10094,6 +10095,65 @@ an [`__arm_streaming`](#arm_streaming) type.
 See [Changing streaming mode locally](#changing-streaming-mode-locally)
 for more information.
 
+### C++ mangling of SME keywords
+
+SME keyword attributes which apply to function types must be included
+in the name mangling of the type, if the mangling would normally include
+the return type of the function.
+
+SME attributes are mangled in the same way as a template:
+
+``` c
+  template<typename, uint64_t> __SME_ATTRS;
+```
+
+with the arguments:
+
+``` c
+  __SME_ATTRS<normal_function_type, sme_state>;
+```
+
+where:
+
+* normal_function_type is the function type without any SME attributes.
+
+* sme_state is an unsigned 64-bit integer representing the streaming and ZA
+  properties of the function's interface.
+
+The bits are defined as follows:
+
+| **Bits** | **Value** | **Interface Type**             |
+| -------- | --------- | ------------------------------ |
+| 0        | 0b1       | __arm_streaming                |
+| 1        | 0b1       | __arm_streaming_compatible     |
+| 2        | 0b1       | __arm_agnostic("sme_za_state") |
+| 3-5      | 0b000     | No ZA state (default)          |
+|          | 0b001     | __arm_in("za")                 |
+|          | 0b010     | __arm_out("za")                |
+|          | 0b011     | __arm_inout("za")              |
+|          | 0b100     | __arm_preserves("za")          |
+| 6-8      | 0b000     | No ZT0 state (default)         |
+|          | 0b001     | __arm_in("zt0")                |
+|          | 0b010     | __arm_out("zt0")               |
+|          | 0b011     | __arm_inout("zt0")             |
+|          | 0b100     | __arm_preserves("zt0")         |
+
+Bits 9-63 are defined to be zero by this revision of the ACLE and are reserved
+for future type attributes.
+
+For example:
+
+``` c
+  // Mangled as _Z1fP11__SME_ATTRSIFu10__SVInt8_tvELj1EE
+  void f(svint8_t (*fn)() __arm_streaming) { fn(); }
+
+  // Mangled as _Z1fP11__SME_ATTRSIFu10__SVInt8_tvELj26EE
+  void f(svint8_t (*fn)() __arm_streaming_compatible __arm_inout("za")) { fn(); }
+
+  // Mangled as _Z1fP11__SME_ATTRSIFu10__SVInt8_tvELj128EE
+  void f(svint8_t (*fn)() __arm_out("zt0")) { fn(); }
+```
+
 ## SME types
 
 ### Predicate-as-counter