[llvm] [AMDGPU] Don't optimize agpr phis if the operand doesn't have subreg use (PR #91267)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,40 @@
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx908 -verify-machineinstrs -run-pass si-fold-operands -o - %s | FileCheck %s
+
+# CHECK-NOT: V_ACCVGPR_READ_B32_e64
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arsenm wrote:

Positive checks are much more reliable 

https://github.com/llvm/llvm-project/pull/91267