[PATCH] D70129: [AArch64] [FrameLowering] Allow conditional insertion of CFI instruction

[David Tellenbach via Phabricator via llvm-commits]

tellenbach created this revision.
Herald added subscribers: llvm-commits, hiraditya, kristof.beyls.
Herald added a project: LLVM.
tellenbach added reviewers: t.p.northover, ostannard.

The insertion of most CFI instructions during AArch64 frame lowering can
be disabled (e.g. using the function attribute `nounwind`).

This patch enables conditional insertion for one more CFI instruction.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70129

Files:
  llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
  llvm/test/CodeGen/AArch64/no_cfi.ll


Index: llvm/test/CodeGen/AArch64/no_cfi.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/no_cfi.ll
@@ -0,0 +1,13 @@
+; RUN: llc -mtriple aarch64-arm-linux-fnu -o - %s | FileCheck %s
+
+; CHECK:        a:                                      // @a
+; CHECK-NEXT:   // %bb.0:
+; CHECK-NEXT:           sub     sp, sp, #16
+; CHECK-NOT:            .cfi{{.*}}
+; CHECK:                ret
+define void @a() nounwind {
+  %1 = alloca i32, align 4
+  store i32 1, i32* %1, align 4
+  ret void
+}
+
Index: llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -933,12 +933,14 @@
       if (!NeedsWinCFI) {
         // Label used to tie together the PROLOG_LABEL and the MachineMoves.
         MCSymbol *FrameLabel = MMI.getContext().createTempSymbol();
-        // Encode the stack size of the leaf function.
-        unsigned CFIIndex = MF.addFrameInst(
-            MCCFIInstruction::createDefCfaOffset(FrameLabel, -NumBytes));
-        BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
-            .addCFIIndex(CFIIndex)
-            .setMIFlags(MachineInstr::FrameSetup);
+        if (needsFrameMoves) {
+          // Encode the stack size of the leaf function.
+          unsigned CFIIndex = MF.addFrameInst(
+              MCCFIInstruction::createDefCfaOffset(FrameLabel, -NumBytes));
+          BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+              .addCFIIndex(CFIIndex)
+              .setMIFlags(MachineInstr::FrameSetup);
+        }
       }
     }
 


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