[llvm] AMDGPU: Add baseline test for coalescing vgpr to agpr subreg inserts (PR #130877)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,519 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx950 -run-pass=register-coalescer -verify-coalescing -o - %s | FileCheck %s
+
+# Test coalescing situations which can use av_* registers to handle
+# copies between VGPRs and AGPRs.
+
+
+# Should coalesce %0 and %1 into subregisters of the av_64 common
+# class
+---
+name: copy_vgpr32_to_areg64_coalesce_with_av64
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0, $vgpr1
+
+    ; CHECK-LABEL: name: copy_vgpr32_to_areg64_coalesce_with_av64
+    ; CHECK: liveins: $vgpr0, $vgpr1
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:vgpr_32 = COPY $vgpr0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:vgpr_32 = COPY $vgpr1
+    ; CHECK-NEXT: undef [[COPY2:%[0-9]+]].sub0:areg_64 = COPY [[COPY]]
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]].sub1:areg_64 = COPY [[COPY1]]
+    ; CHECK-NEXT: INLINEASM &"; use $0", 0 /* attdialect */, 3473417 /* reguse:AReg_64 */, [[COPY2]]
+    ; CHECK-NEXT: SI_RETURN
+    %0:vgpr_32 = COPY $vgpr0
+    %1:vgpr_32 = COPY $vgpr1
+    undef %2.sub0:areg_64 = COPY %0
+    %2.sub1:areg_64 = COPY %1
+    INLINEASM &"; use $0", 0 /* attdialect */, 3473417 /* reguse:AReg_64 */, killed %2
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arsenm wrote:

This is precisely why this is using inlineasm, and not an arbitrary implicit use. The constraint here should be fixed 

https://github.com/llvm/llvm-project/pull/130877