[Lldb-commits] [lldb] [lldb][AArch64] Correctly invalidate svg when vg is written (PR #140875)

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llvmbot wrote:


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@llvm/pr-subscribers-lldb

Author: David Spickett (DavidSpickett)

<details>
<summary>Changes</summary>

Recently the Linux Kernel has fixed a bunch of issues in SME support and while testing that, I found two tests failing: FAIL: test_za_register_dynamic_config_main_disabled (TestZAThreadedDynamic.AArch64ZAThreadedTestCase) FAIL: test_za_register_dynamic_config_main_enabled (TestZAThreadedDynamic.AArch64ZAThreadedTestCase)

These tests write to vg during streaming mode from lldb and expect to see that za has been resized to match it. Instead, it was unavilable. lldb-server was sending the correct amount of data but lldb client was expect the old size.

Turns out that instead of a write to vg invalidating svg, it was invalidating... something else. I'm still not sure how these tests ever worked but with this one line fix, they pass again.

I did not see this issue with SVE or streaming SVE Z registers because those always resize using the value of vg, and vg always has the value we just wrote.

(remember that vg is the vector length of the **current** mode, not of non-streaming mode, whereas svg is the vector length of streaming mode, even if you are currently in non-streaming mode)

---
Full diff: https://github.com/llvm/llvm-project/pull/140875.diff


1 Files Affected:

- (modified) lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.cpp (+1-1) 


``````````diff
diff --git a/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.cpp b/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.cpp
index c004c0f3c3cf5..f2095c150609f 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.cpp
+++ b/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.cpp
@@ -425,7 +425,7 @@ void RegisterInfoPOSIX_arm64::AddRegSetSME(bool has_zt) {
   //
   // This must be added now, rather than when vg is defined because SME is a
   // dynamic set that may or may not be present.
-  static uint32_t vg_invalidates[] = {sme_regnum + 1 /*svg*/,
+  static uint32_t vg_invalidates[] = {first_sme_regnum + 1 /*svg*/,
                                       LLDB_INVALID_REGNUM};
   m_dynamic_reg_infos[GetRegNumSVEVG()].invalidate_regs = vg_invalidates;
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/140875