[llvm] [AMDGPU] Don't realign already allocated LDS. Point fix for 106412 (PR #106421)

[Jon Chesterfield via llvm-commits]

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@@ -0,0 +1,15 @@
+; RUN: opt -S -mtriple=amdgcn-- -amdgpu-lower-module-lds < %s | FileCheck %s
+
+; Can't have a second variable without absolute_symbol showing it is realigned as
+; there is a fatal error on mixing absolute and non-absolute symbols
+
+; CHECK: @lds.dont_realign = internal addrspace(3) global i64 undef, align 2, !absolute_symbol !0
+ at lds.dont_realign = internal addrspace(3) global i64 undef, align 2, !absolute_symbol !0
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JonChesterfield wrote:

Poison takes it for the test case, but in general it seems unfortunate. Reading from uninitialised LDS could be totally well defined and making it poison will propagate dead code elimination from it, though I concede that is the direction LLVM is moving in

https://github.com/llvm/llvm-project/pull/106421