[mips][micromips] Fix how values in .gcc_except_table are calculated

When a landing pad is calculated in a program that is compiled for micromips
with -fPIC flag, it will point to an even address.
Such an error will cause a segmentation fault, as the instructions in
micromips are aligned on odd addresses. This patch sets the last bit of the
offset where a landing pad is, to 1, which will effectively be an odd
address and point to the instruction exactly.

r344591 fixed this issue for -static compilation.

Patch by Aleksandar Beserminji.

Differential Revision: https://reviews.llvm.org/D57677

llvm-svn: 353480

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index d8091e41f1a..7ca935f248d 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -558,6 +558,11 @@ static void AttemptToFoldSymbolOffsetDifference(
   if (Asm->isThumbFunc(&SA))
     Addend |= 1;
 
+  // If symbol is labeled as micromips, we set low-bit to ensure
+  // correct offset in .gcc_except_table
+  if (Asm->getBackend().isMicroMips(&SA))
+    Addend |= 1;
+
   // Clear the symbol expr pointers to indicate we have folded these
   // operands.
   A = B = nullptr;