third_party/llvm-7.0/llvm/test/CodeGen/X86/pre-coalesce.mir

# RUN: llc -mtriple=x86_64-unknown-linux-gnu -run-pass simple-register-coalescing -o - %s | FileCheck %s
# Check there is no partial redundent copy left in the loop after register coalescing.
--- |
  ; ModuleID = '<stdin>'
  source_filename = "<stdin>"
  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
  target triple = "x86_64-unknown-linux-gnu"
  
  @b = common local_unnamed_addr global i8* null, align 8
  @a = common local_unnamed_addr global i32 0, align 4
  
  define i32 @foo() local_unnamed_addr {
  entry:
    %t0 = load i8*, i8** @b, align 8
    %t1 = load i8, i8* %t0, align 1
    %cmp4 = icmp eq i8 %t1, 0
    %t2 = load i32, i32* @a, align 4
    br i1 %cmp4, label %while.end, label %while.body.preheader
  
  while.body.preheader:                             ; preds = %entry
    br label %while.body
  
  while.body:                                       ; preds = %while.body, %while.body.preheader
    %t3 = phi i32 [ %add3, %while.body ], [ %t2, %while.body.preheader ]
    %t4 = phi i8 [ %t5, %while.body ], [ %t1, %while.body.preheader ]
    %conv = sext i8 %t4 to i32
    %add = mul i32 %t3, 33
    %add3 = add nsw i32 %add, %conv
    store i32 %add3, i32* @a, align 4
    %t5 = load i8, i8* %t0, align 1
    %cmp = icmp eq i8 %t5, 0
    br i1 %cmp, label %while.end, label %while.body
  
  while.end:                                        ; preds = %while.body, %entry
    %.lcssa = phi i32 [ %t2, %entry ], [ %add3, %while.body ]
    ret i32 %.lcssa
  }

...
---
# Check A = B and B = A copies will not exist in the loop at the same time.
# CHECK: name: foo
# CHECK: [[L1:bb.3]].{{[a-zA-Z0-9.]+}}:
# CHECK: %[[REGA:.*]] = COPY %[[REGB:.*]]
# CHECK-NOT: %[[REGB]] = COPY %[[REGA]]
# CHECK: JNE_1 %[[L1]]

name:            foo
alignment:       4
exposesReturnsTwice: false
legalized:       false
regBankSelected: false
selected:        false
tracksRegLiveness: true
registers:       
  - { id: 0, class: gr64 }
  - { id: 1, class: gr8 }
  - { id: 2, class: gr32 }
  - { id: 3, class: gr32 }
  - { id: 4, class: gr8 }
  - { id: 5, class: gr32 }
  - { id: 6, class: gr8 }
  - { id: 7, class: gr32 }
  - { id: 8, class: gr32 }
  - { id: 9, class: gr32 }
  - { id: 10, class: gr32 }
  - { id: 11, class: gr32 }
  - { id: 12, class: gr8 }
  - { id: 13, class: gr32 }
frameInfo:       
  isFrameAddressTaken: false
  isReturnAddressTaken: false
  hasStackMap:     false
  hasPatchPoint:   false
  stackSize:       0
  offsetAdjustment: 0
  maxAlignment:    0
  adjustsStack:    false
  hasCalls:        false
  maxCallFrameSize: 0
  hasOpaqueSPAdjustment: false
  hasVAStart:      false
  hasMustTailInVarArgFunc: false
body:             |
  bb.0.entry:
    %0 = MOV64rm $rip, 1, $noreg, @b, $noreg :: (dereferenceable load 8 from @b)
    %12 = MOV8rm %0, 1, $noreg, 0, $noreg :: (load 1 from %ir.t0)
    TEST8rr %12, %12, implicit-def $eflags
    %11 = MOV32rm $rip, 1, $noreg, @a, $noreg :: (dereferenceable load 4 from @a)
    JNE_1 %bb.1, implicit killed $eflags
  
  bb.4:
    %10 = COPY %11
    JMP_1 %bb.3
  
  bb.1.while.body.preheader:

  bb.2.while.body:
    %8 = MOVSX32rr8 %12
    %10 = COPY %11
    %10 = SHL32ri %10, 5, implicit-def dead $eflags
    %10 = ADD32rr %10, %11, implicit-def dead $eflags
    %10 = ADD32rr %10, %8, implicit-def dead $eflags
    MOV32mr $rip, 1, $noreg, @a, $noreg, %10 :: (store 4 into @a)
    %12 = MOV8rm %0, 1, $noreg, 0, $noreg :: (load 1 from %ir.t0)
    TEST8rr %12, %12, implicit-def $eflags
    %11 = COPY %10
    JNE_1 %bb.2, implicit killed $eflags
    JMP_1 %bb.3
  
  bb.3.while.end:
    $eax = COPY %10
    RET 0, killed $eax

...