[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, 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.

Differential Revision: https://reviews.llvm.org/D52985

llvm-svn: 344591

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index a4458e64bd3..38f311be7c6 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -526,6 +526,11 @@ 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;