[llvm-readobj] [ARMWinEH] Fix printing of exception handlers with packed epilogues

[mstorsjo]

Summary

If there's a packed epilogue (indicated by the flag E), the EpilogueCount() field actually should be interpreted as EpilogueOffset.

[efriedma]

LGTM

[MaskRay]

llvm/test/tools/llvm-readobj/COFF/arm64-packed-epilog.s

2

If the format is important:

# RUN: llvm-mc -filetype=obj -triple aarch64-windows %s -o - |
# RUN:   llvm-readobj --unwind - | FileCheck %s --match-full-lines --strict-whitespace

#      CHECK:ExceptionData {
# CHECK-NEXT:  FunctionLength: 4

@grimar may prefer keeping the temporary file as %t

[grimar]

llvm/test/tools/llvm-readobj/COFF/arm64-packed-epilog.s

2

Yes, I find it is much more convenient for debugging broken tests to have them.
It helps to save time - instead of rewriting (and then reverting) such constructions you can just debug an existent temp file.

[mstorsjo]

llvm/test/tools/llvm-readobj/COFF/arm64-packed-epilog.s

2

Sure, I can change that.

A number of the existing related testcases also use the temp-less form, but I can change to using temp files for the newly added tests at least, and cases where I otherwise touch the RUN lines.

[grimar]

llvm/test/tools/llvm-readobj/COFF/arm64-packed-epilog.s

2

Sounds good, thanks!

llvm/include/llvm/Support/ARMWinEH.h

const size_t Offset = HeaderWords(*this)
                         + (E() ? 0 :  EpilogueCount());
     const uint8_t *ByteCode =
       reinterpret_cast<const uint8_t *>(&Data[Offset]);
     return makeArrayRef(ByteCode, CodeWords() * sizeof(uint32_t));
   }
 
   uint32_t ExceptionHandlerRVA() const {
     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
-    return Data[HeaderWords(*this) + EpilogueCount() + CodeWords()];
+    return Data[HeaderWords(*this) + (E() ? 0 : EpilogueCount()) + CodeWords()];
   }
 
   uint32_t ExceptionHandlerParameter() const {
     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
-    return Data[HeaderWords(*this) + EpilogueCount() + CodeWords() + 1];
+    return Data[HeaderWords(*this) + (E() ? 0 : EpilogueCount()) + CodeWords() +
+                1];
   }
 };
 
 inline size_t HeaderWords(const ExceptionDataRecord &XR) {
   if (XR.isAArch64)
     return (XR.Data[0] & 0xffc00000) ? 1 : 2;
   return (XR.Data[0] & 0xff800000) ? 1 : 2;
 }
 }
 }
 }
 
 #endif

llvm/test/tools/llvm-readobj/COFF/arm64-packed-epilog.s

+// REQUIRES: aarch64-registered-target
+// RUN: llvm-mc -filetype=obj -triple aarch64-windows %s -o - \
+// RUN:   | llvm-readobj --unwind - | FileCheck %s
+
+// CHECK:          ExceptionData {
+// CHECK-NEXT:       FunctionLength: 4
+// CHECK-NEXT:       Version: 0
+// CHECK-NEXT:       ExceptionData: Yes
+// CHECK-NEXT:       EpiloguePacked: Yes
+// CHECK-NEXT:       EpilogueOffset: 0
+// CHECK-NEXT:       ByteCodeLength: 4
+// CHECK-NEXT:       Prologue [
+// CHECK-NEXT:         0xe4                ; end
+// CHECK-NEXT:       ]
+// CHECK-NEXT:       ExceptionHandler [
+// CHECK-NEXT:         Routine: 0x11223344
+// CHECK-NEXT:         Parameter: 0x55667788
+// CHECK-NEXT:       ]
+
+.section .pdata,"dr"
+        .long func@IMGREL
+        .long "$unwind$func"@IMGREL
+
+        .text
+        .globl  func
+func:
+        ret
+
+.section .xdata,"dr"
+"$unwind$func":
+.byte 0x01, 0x00, 0x30, 0x08
+.byte 0xe4, 0xe3, 0xe3, 0xe3
+.byte 0x44, 0x33, 0x22, 0x11
+.byte 0x88, 0x77, 0x66, 0x55