[llvm] [AIX][TLS] Produce a faster local-exec access sequence for the "aix-small-tls" global variable attribute (PR #83053)

[zhijian lin via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
+; RUN: llc  -verify-machineinstrs -mcpu=pwr7 -ppc-asm-full-reg-names \
+; RUN:      -mtriple powerpc64-ibm-aix-xcoff < %s \
+; RUN:      | FileCheck %s --check-prefix=CHECK-SMALLCM64
+; RUN: llc  -verify-machineinstrs -mcpu=pwr7 -ppc-asm-full-reg-names \
+; RUN:      -mtriple powerpc64-ibm-aix-xcoff --code-model=large \
+; RUN:      < %s | FileCheck %s --check-prefix=CHECK-LARGECM64
+
+ at mySmallLocalExecTLS6 = external thread_local(localexec) global [60 x i64], align 8
+ at mySmallLocalExecTLS2 = external thread_local(localexec) global [3000 x i64], align 8 #0
+ at MyTLSGDVar = thread_local global [800 x i64] zeroinitializer, align 8
+ at mySmallLocalExecTLS3 = internal thread_local(localexec) global [3000 x i64] zeroinitializer, align 8
+ at mySmallLocalExecTLS4 = internal thread_local(localexec) global [3000 x i64] zeroinitializer, align 8 #0
+ at mySmallLocalExecTLS5 = thread_local(localexec) global [3000 x i64] zeroinitializer, align 8 #0
+ at mySmallLocalExecTLS = thread_local(localexec) local_unnamed_addr global [7800 x i64] zeroinitializer, align 8 #0
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diggerlin wrote:

general question for all the test cases in the patch. do we still need so many thread_local(localexec) variable to test  the feature, can we reduce the test case?  for example : 
`@mySmallLocalExecTLS = thread_local(localexec) local_unnamed_addr global [7800 x i64] zeroinitializer, align 8 #0`

but never check it in the test case ?

https://github.com/llvm/llvm-project/pull/83053