X86: Do splat promotion later, so the optimizer can chew on it first.
This catches many cases where we can emit a more efficient shuffle for a
specific mask or when the mask contains undefs. Once the splat is lowered to
unpacks we can't do that anymore.
There is a possibility of moving the promotion after pshufb matching, but I'm
not sure if pshufb with a mask loaded from memory is faster than 3 shuffles, so
I avoided that for now.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173569 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 0c12410..6daa9b6 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5839,6 +5839,11 @@
}
}
+ // Promote splats to a larger type which usually leads to more efficient code.
+ // FIXME: Is this true if pshufb is available?
+ if (SVOp->isSplat())
+ return PromoteSplat(SVOp, DAG);
+
// If we have SSSE3, and all words of the result are from 1 input vector,
// case 2 is generated, otherwise case 3 is generated. If no SSSE3
// is present, fall back to case 4.
@@ -5972,6 +5977,11 @@
DebugLoc dl = SVOp->getDebugLoc();
ArrayRef<int> MaskVals = SVOp->getMask();
+ // Promote splats to a larger type which usually leads to more efficient code.
+ // FIXME: Is this true if pshufb is available?
+ if (SVOp->isSplat())
+ return PromoteSplat(SVOp, DAG);
+
// If we have SSSE3, case 1 is generated when all result bytes come from
// one of the inputs. Otherwise, case 2 is generated. If no SSSE3 is
// present, fall back to case 3.
@@ -6669,20 +6679,10 @@
// Handle splat operations
if (SVOp->isSplat()) {
- unsigned NumElem = VT.getVectorNumElements();
-
// Use vbroadcast whenever the splat comes from a foldable load
SDValue Broadcast = LowerVectorBroadcast(Op, DAG);
if (Broadcast.getNode())
return Broadcast;
-
- // Handle splats by matching through known shuffle masks
- if ((VT.is128BitVector() && NumElem <= 4) ||
- (VT.is256BitVector() && NumElem <= 8))
- return SDValue();
-
- // All remaning splats are promoted to target supported vector shuffles.
- return PromoteSplat(SVOp, DAG);
}
// Check integer expanding shuffles.