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648e1e248b
Optionally allow the order of restoring the callee-saved registers in the epilogue to be reversed. The flag -reverse-csr-restore-seq generates the following code: ``` stp x26, x25, [sp, #-64]! stp x24, x23, [sp, #16] stp x22, x21, [sp, #32] stp x20, x19, [sp, #48] ; [..] ldp x24, x23, [sp, #16] ldp x22, x21, [sp, #32] ldp x20, x19, [sp, #48] ldp x26, x25, [sp], #64 ret ``` Note how the CSRs are restored in the same order as they are saved. One exception to this rule is the last `ldp`, which allows us to merge the stack adjustment and the ldp into a post-index ldp. This is done by first generating: ldp x26, x27, [sp] add sp, sp, #64 which gets merged by the arm64 load store optimizer into ldp x26, x25, [sp], #64 The flag is disabled by default. llvm-svn: 327569
73 lines
2.4 KiB
YAML
73 lines
2.4 KiB
YAML
# RUN: llc -run-pass=prologepilog -reverse-csr-restore-seq -o - -mtriple=aarch64-- %s | FileCheck %s --check-prefixes=CHECK,BEFORELDSTOPT
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# RUN: llc -start-before=prologepilog -stop-after=aarch64-ldst-opt -reverse-csr-restore-seq -o - -mtriple=aarch64-- %s | FileCheck %s --check-prefixes=CHECK,AFTERLDSTOPT
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#
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--- |
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define void @foo() nounwind { entry: unreachable }
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define void @bar() nounwind { entry: unreachable }
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...
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---
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name: foo
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# CHECK-LABEL: name: foo
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tracksRegLiveness: true
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body: |
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bb.0:
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$x19 = IMPLICIT_DEF
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$x20 = IMPLICIT_DEF
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$x21 = IMPLICIT_DEF
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$x22 = IMPLICIT_DEF
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$x23 = IMPLICIT_DEF
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$x24 = IMPLICIT_DEF
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$x25 = IMPLICIT_DEF
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$x26 = IMPLICIT_DEF
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; The local stack size is 0, so the last ldp in the sequence will also
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; restore the stack.
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; CHECK: $x24, $x23 = frame-destroy LDPXi $sp, 2
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; CHECK-NEXT: $x22, $x21 = frame-destroy LDPXi $sp, 4
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; CHECK-NEXT: $x20, $x19 = frame-destroy LDPXi $sp, 6
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; Before running the load-store optimizer, we emit a ldp and an add.
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; BEFORELDSTOPT-NEXT: $x26, $x25 = frame-destroy LDPXi $sp, 0
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; BEFORELDSTOPT-NEXT: $sp = frame-destroy ADDXri $sp, 64, 0
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; We want to make sure that after running the load-store optimizer, the ldp
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; and the add get merged into a post-index ldp.
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; AFTERLDSTOPT-NEXT: early-clobber $sp, $x26, $x25 = frame-destroy LDPXpost $sp, 8
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RET_ReallyLR
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...
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---
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name: bar
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# CHECK-LABEL: name: bar
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tracksRegLiveness: true
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stack:
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- { id : 0, size: 8, alignment: 4,
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stack-id: 0, callee-saved-register: '', callee-saved-restored: true,
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local-offset: -4, di-variable: '', di-expression: '', di-location: '' }
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body: |
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bb.0:
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$x19 = IMPLICIT_DEF
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$x20 = IMPLICIT_DEF
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$x21 = IMPLICIT_DEF
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$x22 = IMPLICIT_DEF
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$x23 = IMPLICIT_DEF
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$x24 = IMPLICIT_DEF
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$x25 = IMPLICIT_DEF
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$x26 = IMPLICIT_DEF
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; The local stack size is not 0, and we can combine the CSR stack size with
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; the local stack size. This results in rewriting the offsets for all the
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; save/restores and forbids us to merge the stack adjustment and the last pop.
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; In this case, there is no point of moving the first CSR pair at the end.
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; CHECK: $x26, $x25 = frame-destroy LDPXi $sp, 2
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; CHECK-NEXT: $x24, $x23 = frame-destroy LDPXi $sp, 4
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; CHECK-NEXT: $x22, $x21 = frame-destroy LDPXi $sp, 6
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; CHECK-NEXT: $x20, $x19 = frame-destroy LDPXi $sp, 8
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; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 80, 0
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RET_ReallyLR
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...
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