Fix assert when decoding PSHUFB mask
The PSHUFB mask decode routine used to assert if the mask index was out of
range (<0 or greater than the size of the vector). The problem is, we can
legitimately have a PSHUFB with a large index using intrinsics. The
instruction only uses the least significant 4 bits. This change removes the
assert and masks the index to match the instruction behaviour.
llvm-svn: 218242
diff --git a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
index 51d251e..6d42a10 100644
--- a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
+++ b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
@@ -247,9 +247,8 @@
if (Element & (1 << 7))
ShuffleMask.push_back(SM_SentinelZero);
else {
- int Index = Base + Element;
- assert((Index >= 0 && Index < NumElements) &&
- "Out of bounds shuffle index for pshub instruction!");
+ // Only the least significant 4 bits of the byte are used.
+ int Index = Base + (Element & 0xf);
ShuffleMask.push_back(Index);
}
}
@@ -266,9 +265,8 @@
if (M & (1 << 7))
ShuffleMask.push_back(SM_SentinelZero);
else {
- int Index = Base + M;
- assert((Index >= 0 && (unsigned)Index < RawMask.size()) &&
- "Out of bounds shuffle index for pshub instruction!");
+ // Only the least significant 4 bits of the byte are used.
+ int Index = Base + (M & 0xf);
ShuffleMask.push_back(Index);
}
}