[x86] Based on a long conversation between myself, Jim Grosbach, Hal

Finkel, Eric Christopher, and a bunch of other people I'm probably
forgetting (sorry), add an option to the x86 backend to widen vectors
during type legalization rather than promote them.

This still would promote vNi1 vectors to get the masks right, but would
widen other vectors. A lot of experiments are piling up right now
showing that widening should probably be the default legalization
strategy outside of vNi1 cases, but it is very hard to test the
rammifications of that and fix bugs in widening-based legalization
without an option that enables it. I'll be checking in tests shortly
that use this option to exercise cases where widening doesn't work well
and hopefully we'll be able to switch fully to this soon.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212249 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index f0d8f22210429898c3e9101baa3d8eb831179fc7..ede29662e14262b159abac96aa6b4cfda94b9f9d 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -58,6 +58,12 @@ using namespace llvm;
 
 STATISTIC(NumTailCalls, "Number of tail calls");
 
+static cl::opt<bool> ExperimentalVectorWideningLegalization(
+    "x86-experimental-vector-widening-legalization", cl::init(false),
+    cl::desc("Enable an experimental vector type legalization through widening "
+             "rather than promotion."),
+    cl::Hidden);
+
 static cl::opt<bool> ExperimentalVectorShuffleLowering(
     "x86-experimental-vector-shuffle-lowering", cl::init(false),
     cl::desc("Enable an experimental vector shuffle lowering code path."),
@@ -1588,6 +1594,16 @@ void X86TargetLowering::resetOperationActions() {
   setPrefFunctionAlignment(4); // 2^4 bytes.
 }
 
+TargetLoweringBase::LegalizeTypeAction
+X86TargetLowering::getPreferredVectorAction(EVT VT) const {
+  if (ExperimentalVectorWideningLegalization &&
+      VT.getVectorNumElements() != 1 &&
+      VT.getVectorElementType().getSimpleVT() != MVT::i1)
+    return TypeWidenVector;
+
+  return TargetLoweringBase::getPreferredVectorAction(VT);
+}
+
 EVT X86TargetLowering::getSetCCResultType(LLVMContext &, EVT VT) const {
   if (!VT.isVector())
     return Subtarget->hasAVX512() ? MVT::i1: MVT::i8;

diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 10754825a6dd58f6960edf0bd9486b445ba15da2..c8cdce7c766431b612abaa258e7d67e2bae3c707 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -796,6 +796,9 @@ namespace llvm {
     /// \brief Reset the operation actions based on target options.
     void resetOperationActions() override;
 
+    /// \brief Customize the preferred legalization strategy for certain types.
+    LegalizeTypeAction getPreferredVectorAction(EVT VT) const override;
+
   protected:
     std::pair<const TargetRegisterClass*, uint8_t>
     findRepresentativeClass(MVT VT) const override;