[PATCH] D125876: [MC] [Win64EH] Don't produce packed ARM64 unwind info with homed parameters

[Martin Storsjö via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG924defada9bc: [MC] [Win64EH] Don't produce packed ARM64 unwind info with homed parameters (authored by mstorsjo).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125876/new/

https://reviews.llvm.org/D125876

Files:
  llvm/lib/MC/MCWin64EH.cpp
  llvm/test/MC/AArch64/seh-packed-unwind.s


Index: llvm/test/MC/AArch64/seh-packed-unwind.s
===================================================================
--- llvm/test/MC/AArch64/seh-packed-unwind.s
+++ llvm/test/MC/AArch64/seh-packed-unwind.s
@@ -81,25 +81,10 @@
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }
 // CHECK-NEXT:   RuntimeFunction {
-// CHECK-NEXT:     Function: func5
-// CHECK-NEXT:     Fragment: No
-// CHECK-NEXT:     FunctionLength: 56
-// CHECK-NEXT:     RegF: 0
-// CHECK-NEXT:     RegI: 1
-// CHECK-NEXT:     HomedParameters: Yes
-// CHECK-NEXT:     CR: 0
-// CHECK-NEXT:     FrameSize: 112
-// CHECK-NEXT:     Prologue [
-// CHECK-NEXT:       sub sp, sp, #32
-// CHECK-NEXT:       stp x6, x7, [sp, #64]
-// CHECK-NEXT:       stp x4, x5, [sp, #48]
-// CHECK-NEXT:       stp x2, x3, [sp, #32]
-// CHECK-NEXT:       stp x0, x1, [sp, #16]
-// CHECK-NEXT:       str x19, [sp, #-80]!
-// CHECK-NEXT:       end
-// CHECK-NEXT:     ]
-// CHECK-NEXT:   }
-// CHECK-NEXT:   RuntimeFunction {
+// CHECK-NEXT:     Function: notpacked_func5
+// CHECK-NEXT:     ExceptionRecord:
+// CHECK-NEXT:     ExceptionData {
+// CHECK:        RuntimeFunction {
 // CHECK-NEXT:     Function: func6
 // CHECK-NEXT:     Fragment: No
 // CHECK-NEXT:     FunctionLength: 24
@@ -441,8 +426,8 @@
     ret
     .seh_endproc
 
-func5:
-    .seh_proc func5
+notpacked_func5:
+    .seh_proc notpacked_func5
     str x19, [sp, #-80]!
     .seh_save_reg_x x19, 80
     stp x0,  x1,  [sp, #16]
Index: llvm/lib/MC/MCWin64EH.cpp
===================================================================
--- llvm/lib/MC/MCWin64EH.cpp
+++ llvm/lib/MC/MCWin64EH.cpp
@@ -860,6 +860,16 @@
   if (Nops != 0 && Nops != 4)
     return false;
   int H = Nops == 4;
+  // There's an inconsistency regarding packed unwind info with homed
+  // parameters; according to the documentation, the epilog shouldn't have
+  // the same corresponding nops (and thus, to set the H bit, we should
+  // require an epilog which isn't exactly symmetrical - we shouldn't accept
+  // an exact mirrored epilog for those cases), but in practice,
+  // RtlVirtualUnwind behaves as if it does expect the epilogue to contain
+  // the same nops. See https://github.com/llvm/llvm-project/issues/54879.
+  // To play it safe, don't produce packed unwind info with homed parameters.
+  if (H)
+    return false;
   int IntSZ = 8 * RegI;
   if (StandaloneLR)
     IntSZ += 8;


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