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# Check that we can remove the redundant save of constant registers such as $wzr
# RUN: llc -mtriple=aarch64-unknown-linux %s -verify-machineinstrs -start-before=machine-cp -o - | FileCheck %s --check-prefix ASM
# RUN: llc -mtriple=aarch64-unknown-linux %s -verify-machineinstrs -run-pass=machine-cp -o - | FileCheck %s
--- |
target triple = "aarch64-unknown-linux"
declare i32 @bar(i32) nounwind
define i32 @foo() nounwind {
; ASM-LABEL: foo:
; ASM: // %bb.0:
; ASM-NEXT: str x30, [sp, #-16]! // 8-byte Folded Spill
; ASM-NEXT: mov w0, wzr
; ASM-NEXT: bl bar
; ASM-NEXT: mov w0, wzr
; ASM-NEXT: ldr x30, [sp], #16 // 8-byte Folded Reload
; ASM-NEXT: ret
call i32 @bar(i32 0)
ret i32 0
}
...
---
name: foo
frameInfo:
adjustsStack: true
body: |
bb.0 (%ir-block.0):
; CHECK-LABEL: name: foo
; CHECK: ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
; CHECK-NEXT: $w0 = COPY $wzr
; CHECK-NEXT: BL @bar, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $w0, implicit-def $sp, implicit-def $w0
; CHECK-NEXT: ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
; CHECK-NEXT: $w0 = COPY $wzr
; CHECK-NEXT: RET_ReallyLR implicit $w0
ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
renamable $w19 = COPY $wzr
$w0 = COPY renamable $w19
BL @bar, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $w0, implicit-def $sp, implicit-def $w0
ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
$w0 = COPY killed renamable $w19
RET_ReallyLR implicit $w0
...
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