Get rid of an incorrect optimization for shuffles with PALIGNR and simplify isPALIGNRMask.
Addresses PR10466, although the crash from that PR only triggers in cases where DAGCombine misses optimizing a shuffle.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135980 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index c3fa9d1..d2c8778 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -3075,27 +3075,16 @@
if (i == e)
return false;
- // Determine if it's ok to perform a palignr with only the LHS, since we
- // don't have access to the actual shuffle elements to see if RHS is undef.
- bool Unary = Mask[i] < (int)e;
- bool NeedsUnary = false;
+ // Make sure we're shifting in the right direction.
+ if (Mask[i] <= i)
+ return false;
int s = Mask[i] - i;
// Check the rest of the elements to see if they are consecutive.
for (++i; i != e; ++i) {
int m = Mask[i];
- if (m < 0)
- continue;
-
- Unary = Unary && (m < (int)e);
- NeedsUnary = NeedsUnary || (m < s);
-
- if (NeedsUnary && !Unary)
- return false;
- if (Unary && m != ((s+i) & (e-1)))
- return false;
- if (!Unary && m != (s+i))
+ if (m >= 0 && m != s+i)
return false;
}
return true;
@@ -3631,6 +3620,7 @@
if (Val >= 0)
break;
}
+ assert(Val - i > 0 && "PALIGNR imm should be positive");
return (Val - i) * EltSize;
}