[llvm] [StackSlotColoring] Ignore non-spill objects in RemoveDeadStores. (PR #80242)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,125 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
+# RUN: llc %s -mtriple=riscv64 -run-pass=greedy,virtregrewriter,stack-slot-coloring -o - | FileCheck %s
+
+--- |
+  define void @foo() {
+  entry:
+    ; Dummy test just to hold the alloca
+    %alpha = alloca i32, i32 0, align 4
+    ret void
+  }
+
+...
+---
+name:            foo
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    4
+  localFrameSize:  4
+stack:
+  - { id: 0, name: alpha, size: 1, alignment: 4, local-offset: -4 }
+machineFunctionInfo:
+  varArgsFrameIndex: 0
+  varArgsSaveSize: 0
+body:             |
+  bb.0.entry:
+    ; To trick stack-slot-colouring to run its dead-store-elimination phase,
+    ; which is at fault, we need the register allocator to run, and spill in two
+    ; places that can have their slots merged. Achieve this by volatile-loading
+    ; data into all allocatable GPRs except $x31. Then, volatile storing them
+    ; later, leaving regalloc only $x31 to play with in the middle.
+    $x1 = LW %stack.0.alpha, 0 :: (volatile load (s32) from %ir.alpha)
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arsenm wrote:

you can replace all the MMO IR references with %stack.0 and drop the IR section 

https://github.com/llvm/llvm-project/pull/80242