[PATCH] D35835: [ARM] Use Swift error registers on non-Darwin targets

[Brian Gesiak via Phabricator via llvm-commits]

modocache created this revision.
Herald added subscribers: kristof.beyls, javed.absar, aemerson.

Remove a check for `ARMSubtarget::isTargetDarwin` when determining
whether to use Swift error registers, so that Swift errors work
properly on non-Darwin ARM32 targets (specifically Android).

Before this patch, generated code would save and restores ARM register r8 at
the entry and returns of a function that throws. As r8 is used as a virtual
return value for the object being thrown, this gets overwritten by the restore,
and calling code is unable to catch the error. In turn this caused Swift code
that used `do`/`try`/`catch` to work improperly on Android ARM32 targets.

Addresses Swift bug report https://bugs.swift.org/browse/SR-5438.

Patch by John Holdsworth.


https://reviews.llvm.org/D35835

Files:
  lib/Target/ARM/ARMBaseRegisterInfo.cpp


Index: lib/Target/ARM/ARMBaseRegisterInfo.cpp
===================================================================
--- lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -92,7 +92,7 @@
     }
   }
 
-  if (STI.isTargetDarwin() && STI.getTargetLowering()->supportSwiftError() &&
+  if (STI.getTargetLowering()->supportSwiftError() &&
       F->getAttributes().hasAttrSomewhere(Attribute::SwiftError))
     return CSR_iOS_SwiftError_SaveList;
 
@@ -120,7 +120,7 @@
     // This is academic because all GHC calls are (supposed to be) tail calls
     return CSR_NoRegs_RegMask;
 
-  if (STI.isTargetDarwin() && STI.getTargetLowering()->supportSwiftError() &&
+  if (STI.getTargetLowering()->supportSwiftError() &&
       MF.getFunction()->getAttributes().hasAttrSomewhere(Attribute::SwiftError))
     return CSR_iOS_SwiftError_RegMask;
 


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