[PATCH] D83464: [MachineOutliner][AArch64] Fix for noreturn functions

[Kyungwoo Lee via Phabricator via llvm-commits]

kyulee created this revision.
Herald added subscribers: llvm-commits, danielkiss, hiraditya, kristof.beyls.
Herald added a project: LLVM.

Noreturn functions conservatively require save + restore LR.
When there is no available register, the stack is used to handle LR. If the block contains a call, the outlined function also needs to set a frame on the stack. This caused an assertion failure for .
This checks whether a candidate is MachineOutlinerDefault while requiring the modification of the stack due to a call. If that is the case, outlining is bailed-out to avoid modifying the stack twice.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83464

Files:
  llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
  llvm/test/CodeGen/AArch64/machine-outliner-noreturn-no-stack.mir


Index: llvm/test/CodeGen/AArch64/machine-outliner-noreturn-no-stack.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/machine-outliner-noreturn-no-stack.mir
@@ -0,0 +1,69 @@
+# RUN: llc -mtriple=arm64-apple-ios -run-pass=prologepilog -run-pass=machine-outliner -verify-machineinstrs  %s -o - | FileCheck %s
+
+# Noreturn functions conservatively need to save and restore lr.
+# When there is no available register, the stack is used at call site.
+# If the stack also needs to be set up for a call in the outlined function,
+# bail-out this case since we do not handle adjusting the stack twice.
+
+# CHECK-NOT: OUTLINED_FUNCTION
+
+--- |
+  @g = external global i32
+  define void @stack_1() #0 { ret void }
+  define void @stack_2() #0 { ret void }
+  define void @baz() {
+    ret void
+  }
+  attributes #0 = { noredzone noreturn }
+...
+---
+name:            stack_1
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x4, $x0, $x1, $x2, $x3
+    $w8 = MOVZWi 259, 0
+    $x9 = ADRP target-flags(aarch64-page) @g
+    $x9 = ADDXri $x9, target-flags(aarch64-pageoff, aarch64-nc) @g, 0
+    STRXui  $x9, $x1, 0
+    STRHHui $w8, $x1, 8
+    $w8 = ORRWrs $wzr, $w4, 0, implicit-def $x8
+    STRXui $x8, $x3, 0
+    STPXi $x3, $xzr, $x2, 0
+    $w8 = MOVZWi 271, 0
+    STRHHui $w8, $x2, 8
+    $x8 = ORRXrs $xzr, $x0, 0
+    $x0 = ORRXrs $xzr, $x1, 0
+    $x1 = ORRXrs $xzr, $x2, 0
+    BL @baz, implicit-def dead $lr, implicit $sp, implicit $x8, implicit $x0, implicit $x1, implicit $x3, implicit $x4, implicit-def $sp, implicit-def $x5, implicit-def $x6, implicit-def $x7, implicit-def $x8,  implicit-def $x9, implicit-def $x10,  implicit-def $x11, implicit-def $x12, implicit-def $x13,  implicit-def $x14, implicit-def $x15, implicit-def $x18
+    BRK 1
+...
+---
+name:            stack_2
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x4, $x0, $x1, $x2, $x3
+    $w8 = MOVZWi 259, 0
+    $x9 = ADRP target-flags(aarch64-page) @g
+    $x9 = ADDXri $x9, target-flags(aarch64-pageoff, aarch64-nc) @g, 0
+    STRXui $x9, $x1, 0
+    STRHHui $w8, $x1, 8
+    $w8 = ORRWrs $wzr, $w4, 0, implicit-def $x8
+    STRXui $x8, $x3, 0
+    STPXi $x3, $xzr, $x2, 0
+    $w8 = MOVZWi 271, 0
+    STRHHui $w8, $x2, 8
+    $x8 = ORRXrs $xzr, $x0, 0
+    $x0 = ORRXrs $xzr, $x1, 0
+    $x1 = ORRXrs $xzr, $x2, 0
+    BL @baz, implicit-def dead $lr, implicit $sp, implicit $x8, implicit $x0, implicit $x1, implicit $x3, implicit $x4, implicit-def $sp, implicit-def $x5, implicit-def $x6, implicit-def $x7, implicit-def $x8,  implicit-def $x9, implicit-def $x10,  implicit-def $x11, implicit-def $x12, implicit-def $x13,  implicit-def $x14, implicit-def $x15, implicit-def $x18
+    BRK 1
+...
+---
+name:            baz
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $w0, $lr, $w8
+    RET undef $lr
Index: llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -6195,6 +6195,15 @@
         return outliner::OutlinedFunction();
       }
 
+      // We don't fix up the stack twice.
+      if (std::any_of(RepeatedSequenceLocs.begin(), RepeatedSequenceLocs.end(),
+                      [](const outliner::Candidate &C) {
+                        return C.CallConstructionID == MachineOutlinerDefault;
+                      })) {
+        RepeatedSequenceLocs.clear();
+        return outliner::OutlinedFunction();
+      }
+
       // Save + restore LR.
       NumBytesToCreateFrame += 8;
     }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D83464.276659.patch
Type: text/x-patch
Size: 3673 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200709/cb6340a6/attachment.bin>