release/20.x: [AArch64] PAUTH_PROLOGUE should not be duplicated with PAuthLR (#124775)

[llvmbot]

Backport 36b3c43

Requested by: @ostannard

[llvmbot]

@tmatheson-arm What do you think about merging this PR to the release branch?

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@llvm/pr-subscribers-backend-aarch64

Author: None (llvmbot)

Changes

Backport 36b3c43

Requested by: @ostannard

---

Full diff: https://github.com/llvm/llvm-project/pull/125230.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/AArch64InstrInfo.td (+6-1)
• (added) llvm/test/CodeGen/AArch64/pauthlr-prologue-duplication.mir (+88)

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index d112d4f10e47d9..b77246200db645 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -1773,7 +1773,12 @@ def : InstAlias<"xpaclri", (XPACLRI), 0>;
 
 let Uses = [LR, SP], Defs = [LR] in {
 // Insertion point of LR signing code.
-def PAUTH_PROLOGUE : Pseudo<(outs), (ins), []>, Sched<[]>;
+def PAUTH_PROLOGUE : Pseudo<(outs), (ins), []>, Sched<[]> {
+  // When using PAuthLR, the address of one of the instructions this expands
+  // into is used as an input to the signature calculation, so this must not be
+  // duplicated.
+  let isNotDuplicable = 1;
+}
 // Insertion point of LR authentication code.
 // The RET terminator of the containing machine basic block may be replaced
 // with a combined RETA(A|B) instruction when rewriting this Pseudo.
diff --git a/llvm/test/CodeGen/AArch64/pauthlr-prologue-duplication.mir b/llvm/test/CodeGen/AArch64/pauthlr-prologue-duplication.mir
new file mode 100644
index 00000000000000..5e57604263793c
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/pauthlr-prologue-duplication.mir
@@ -0,0 +1,88 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple aarch64-none-elf -run-pass=block-placement -O3 -o - %s | FileCheck %s
+
+## Check that block-placement does not perform tail duplication on the
+## PAUTH_EPILOGUE instruction. If that happened, the two prologues would use
+## different addresses while calculating the return address signature, so the
+## epilogue could only be correct for (at most) one of them.
+
+--- |
+  define void @test() "frame-pointer"="non-leaf" {
+  entry:
+    ret void
+  }
+
+  declare void @f()
+...
+---
+name:            test
+body:             |
+  ; CHECK-LABEL: name: test
+  ; CHECK: bb.0.entry:
+  ; CHECK-NEXT:   successors: %bb.1(0x30000000), %bb.2(0x50000000)
+  ; CHECK-NEXT:   liveins: $w0, $w1, $lr
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   CBZW renamable $w0, %bb.1
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2:
+  ; CHECK-NEXT:   successors: %bb.3(0x80000000)
+  ; CHECK-NEXT:   liveins: $w0, $w1, $lr
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   B %bb.3
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.3(0x80000000)
+  ; CHECK-NEXT:   liveins: $w1, $lr
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   renamable $w8 = MOVZWi 1, 0
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.3:
+  ; CHECK-NEXT:   successors: %bb.5(0x30000000), %bb.4(0x50000000)
+  ; CHECK-NEXT:   liveins: $w1, $w8, $lr
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   frame-setup PAUTH_PROLOGUE implicit-def $lr, implicit killed $lr, implicit $sp
+  ; CHECK-NEXT:   CBZW killed renamable $w1, %bb.5
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.4:
+  ; CHECK-NEXT:   successors: %bb.5(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   BL @f, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.5:
+  ; CHECK-NEXT:   BL @f, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp
+  ; CHECK-NEXT:   frame-destroy PAUTH_EPILOGUE implicit-def $lr, implicit killed $lr, implicit $sp
+  ; CHECK-NEXT:   TCRETURNdi @f, 0, csr_aarch64_aapcs, implicit $sp
+  bb.0.entry:
+    successors: %bb.1(0x30000000), %bb.2(0x50000000)
+    liveins: $w0, $w1, $lr
+
+    CBNZW renamable $w0, %bb.2
+
+  bb.1:
+    successors: %bb.3(0x80000000)
+    liveins: $w1, $lr
+
+    renamable $w8 = MOVZWi 1, 0
+    B %bb.3
+
+  bb.2:
+    successors: %bb.3(0x80000000)
+    liveins: $w0, $w1, $lr
+
+  bb.3:
+    successors: %bb.5(0x30000000), %bb.4(0x50000000)
+    liveins: $w1, $w8, $lr
+
+    frame-setup PAUTH_PROLOGUE implicit-def $lr, implicit killed $lr, implicit $sp
+    CBZW killed renamable $w1, %bb.5
+
+  bb.4:
+    successors: %bb.5(0x80000000)
+
+    BL @f, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp
+
+  bb.5:
+    BL @f, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp
+    frame-destroy PAUTH_EPILOGUE implicit-def $lr, implicit killed $lr, implicit $sp
+    TCRETURNdi @f, 0, csr_aarch64_aapcs, implicit $sp
+...

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