[llvm] [RegisterCoalescer] Deferring deletion of instructions in `ErasedInstrs` until the end of an iteration (PR #79820)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,95 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc < %s -mtriple=x86_64 -- | FileCheck %s
+
+define i32 @h(i1 %0, i32 %1) {
+; CHECK-LABEL: h:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl $1, %eax
+; CHECK-NEXT:    movabsq $9166129423, %rcx # imm = 0x22258090F
+; CHECK-NEXT:    xorl %edx, %edx
+; CHECK-NEXT:    jmp .LBB0_1
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_9: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    testb $1, %dil
+; CHECK-NEXT:    jne .LBB0_10
+; CHECK-NEXT:  .LBB0_1: # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    testq %rdx, %rdx
+; CHECK-NEXT:    jne .LBB0_2
+; CHECK-NEXT:  # %bb.7: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testb $1, %dil
+; CHECK-NEXT:    jne .LBB0_9
+; CHECK-NEXT:  # %bb.8: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movq %rcx, %rdx
+; CHECK-NEXT:    jmp .LBB0_9
+; CHECK-NEXT:  .LBB0_2: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testb $1, %dil
+; CHECK-NEXT:    testb $1, %dil
+; CHECK-NEXT:    je .LBB0_4
+; CHECK-NEXT:  # %bb.3: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:  .LBB0_4: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    cmpl $1, %esi
+; CHECK-NEXT:    je .LBB0_1
+; CHECK-NEXT:  # %bb.5:
+; CHECK-NEXT:    movl %eax, %r8d
+; CHECK-NEXT:    testl %esi, %esi
+; CHECK-NEXT:    movl %esi, %eax
+; CHECK-NEXT:    jne .LBB0_6
+; CHECK-NEXT:  .LBB0_10:
+; CHECK-NEXT:    retq
+; CHECK-NEXT:  .LBB0_6: # %.loopexit1
+; CHECK-NEXT:    movl %r8d, %eax
+; CHECK-NEXT:    retq
+  br label %3
+
+3:                                                ; preds = %16, %2
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arsenm wrote:

Run instnamer on this 

https://github.com/llvm/llvm-project/pull/79820