llvm-project/llvm/test/CodeGen/AMDGPU/phi-elimination-assertion.mir

# RUN: llc -mtriple amdgcn -run-pass livevars -run-pass phi-node-elimination -o - %s | FileCheck %s

################################################################################
# This test used to hit an assert in PHIElimination:
#  PHIElimination::LowerPHINode(llvm::MachineBasicBlock&, llvm::MachineBasicBlock::iterator): Assertion `KillInst->readsRegister(SrcReg) && "Cannot find kill instruction"'

---
name:            foo
tracksRegLiveness: true
body:             |
  bb.0:
    S_CBRANCH_SCC0 %bb.2, implicit undef $scc

  bb.1:
    %1:sreg_32_xm0 = S_MOV_B32 255
    S_BRANCH %bb.3

  bb.2:
    %2:sreg_32_xm0 = S_MOV_B32 254

  bb.3:
    dead %3:sreg_32_xm0 = PHI undef %2, %bb.2, undef %1, %bb.1
    %4:sreg_32_xm0 = PHI %2, %bb.2, %1, %bb.1
    S_NOP 0, implicit %4
...

# CHECK-LABEL: name:            foo
# CHECK:   bb.3:
# CHECK-NEXT:     dead %2:sreg_32_xm0 = IMPLICIT_DEF
# CHECK-NEXT:     %3:sreg_32_xm0 = COPY killed %4
# CHECK-NEXT:     S_NOP 0, implicit killed %3


################################################################################
# Similar test as above, but with swapped order for the PHI nodes.
# With this PHI node order we did not hit the assert, but we used to get
#
#  bb.3:
#    dead %3:sreg_32_xm0 = COPY killed %4
#    %2:sreg_32_xm0 = COPY %4
#    S_NOP 0, implicit killed %2
#
# which looks weird regarding killed flags for %4.

---
name:            bar
tracksRegLiveness: true
body:             |
  bb.0:
    S_CBRANCH_SCC0 %bb.2, implicit undef $scc

  bb.1:
    %1:sreg_32_xm0 = S_MOV_B32 255
    S_BRANCH %bb.3

  bb.2:
    %2:sreg_32_xm0 = S_MOV_B32 254

  bb.3:
    %4:sreg_32_xm0 = PHI %2, %bb.2, %1, %bb.1
    dead %3:sreg_32_xm0 = PHI undef %2, %bb.2, undef %1, %bb.1
    S_NOP 0, implicit %4
...

# CHECK-LABEL: name:            bar
# CHECK:   bb.3:
# CHECK-NEXT:     dead %3:sreg_32_xm0 = IMPLICIT_DEF
# CHECK-NEXT:     %2:sreg_32_xm0 = COPY killed %4
# CHECK-NEXT:     S_NOP 0, implicit killed %2


# The following test crashes in phi-elimination hooks.
#

---
name:            bax
tracksRegLiveness: true
body:             |
  bb.0:
    S_CBRANCH_SCC0 %bb.2, implicit undef $scc

  bb.1:
    %1:sreg_32_xm0 = S_MOV_B32 255
    S_BRANCH %bb.3

  bb.2:
    %2:sreg_32_xm0 = S_MOV_B32 254

  bb.3:
    %3:sreg_32_xm0 = PHI %2, %bb.2, %1, %bb.1
...

# CHECK-LABEL: name:            bax
# CHECK:   bb.3:
# CHECK-NEXT:     %2:sreg_32_xm0 = COPY killed %3