[llvm] remove redundant waitcnts (PR #75785)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,136 @@
+# NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+# RUN: llc -march=amdgcn -start-before=si-insert-waitcnts -mcpu=gfx1030 -verify-machineinstrs -o - %s | FileCheck %s
+
+--- |
+  define amdgpu_ps <4 x float> @test_waterfall_multi_begin(ptr addrspace(4) inreg %in, ptr addrspace(4) inreg %s_in, i32 %idx1, i32 %idx2, i32 %s_idx, i32 %s_idx2) #0 {
+  ; CHECK-LABEL: test_waterfall_multi_begin:
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arsenm wrote:

ISA checks in the IR section for a MIR test is extremely weird looking 

https://github.com/llvm/llvm-project/pull/75785