[llvm] [MachineOutliner] Preserve instruction bundles (PR #106402)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Simon Tatham (statham-arm)

<details>
<summary>Changes</summary>

When the machine outliner copies instructions from a source function into an outlined function, it was doing it using `CloneMachineInstr`, which is documented as not preserving the interior of any instruction bundle. So outlining code that includes an instruction bundle would fail, because in the outlined version, the bundle would be empty, so instructions would go missing in the move.

This occurs when any bundled instruction appears in the outlined code, so there was no need to construct an unusual test case: I've just copied a function from the existing `stp-opt-with-renaming.mir`, which happens to contain an SVE instruction bundle. Including two identical copies of that function makes the outliner merge them, and then we check that it didn't destroy the interior of the bundle in the process.

---
Full diff: https://github.com/llvm/llvm-project/pull/106402.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/MachineOutliner.cpp (+3-4) 
- (added) llvm/test/CodeGen/AArch64/machine-outliner-bundle.mir (+54) 


``````````diff
diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp
index 42f410c277179b..9678534cffce09 100644
--- a/llvm/lib/CodeGen/MachineOutliner.cpp
+++ b/llvm/lib/CodeGen/MachineOutliner.cpp
@@ -763,10 +763,9 @@ MachineFunction *MachineOutliner::createOutlinedFunction(
       BuildMI(MBB, MBB.end(), DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(MF.addFrameInst(CFI));
     } else {
-      MachineInstr *NewMI = MF.CloneMachineInstr(&MI);
-      NewMI->dropMemRefs(MF);
-      NewMI->setDebugLoc(DL);
-      MBB.insert(MBB.end(), NewMI);
+      MachineInstr &NewMI = MF.cloneMachineInstrBundle(MBB, MBB.end(), MI);
+      NewMI.dropMemRefs(MF);
+      NewMI.setDebugLoc(DL);
     }
   }
 
diff --git a/llvm/test/CodeGen/AArch64/machine-outliner-bundle.mir b/llvm/test/CodeGen/AArch64/machine-outliner-bundle.mir
new file mode 100644
index 00000000000000..1dd5b0811bdfb6
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/machine-outliner-bundle.mir
@@ -0,0 +1,54 @@
+# RUN: llc -mtriple=aarch64 -run-pass=machine-outliner \
+# RUN: -verify-machineinstrs %s -o - | FileCheck %s
+
+# CHECK: name: OUTLINED_FUNCTION_0
+# CHECK-NOT: name:
+# CHECK: BUNDLE implicit-def $z3, implicit-def $q3, implicit-def $d3, implicit-def $s3, implicit-def $h3, implicit-def $b3, implicit $z19, implicit $p0, implicit $z16 {
+# CHECK:     $z3 = MOVPRFX_ZZ $z19
+# CHECK:     $z3 = FMUL_ZPmZ_S renamable $p0, killed $z3, renamable $z16
+# CHECK: }
+
+---
+name:            bundled
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+  maxCallFrameSize: 0
+machineFunctionInfo:
+  hasRedZone:      false
+body:             |
+  bb.0.entry:
+    liveins: $z3, $z19, $p0, $z16
+    renamable $q0 = LDRQui $sp, 1 :: (load 16)
+    STRSui renamable $s0, $sp, 9, implicit killed $q0 :: (store (s32))
+    BUNDLE implicit-def $z3, implicit-def $q3, implicit-def $d3, implicit-def $s3, implicit-def $h3, implicit-def $b3, implicit $z19, implicit $p0, implicit $z16 {
+      $z3 = MOVPRFX_ZZ $z19
+      $z3 = FMUL_ZPmZ_S renamable $p0, killed $z3, renamable $z16
+    }
+    renamable $q0 = LDRQui $sp, 0 :: (load 16, align 32)
+    STRSui renamable $s0, $sp, 10, implicit killed $q0 :: (store (s32))
+    RET undef $lr
+...
+---
+name:            bundled_clone
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+  maxCallFrameSize: 0
+machineFunctionInfo:
+  hasRedZone:      false
+body:             |
+  bb.0.entry:
+    liveins: $z3, $z19, $p0, $z16
+    renamable $q0 = LDRQui $sp, 1 :: (load 16)
+    STRSui renamable $s0, $sp, 9, implicit killed $q0 :: (store (s32))
+    BUNDLE implicit-def $z3, implicit-def $q3, implicit-def $d3, implicit-def $s3, implicit-def $h3, implicit-def $b3, implicit $z19, implicit $p0, implicit $z16 {
+      $z3 = MOVPRFX_ZZ $z19
+      $z3 = FMUL_ZPmZ_S renamable $p0, killed $z3, renamable $z16
+    }
+    renamable $q0 = LDRQui $sp, 0 :: (load 16, align 32)
+    STRSui renamable $s0, $sp, 10, implicit killed $q0 :: (store (s32))
+    RET undef $lr
+...

``````````

</details>


https://github.com/llvm/llvm-project/pull/106402