[InstCombine][x86] Constant fold psll intrinsics.

This excludes avx512 as I don't have hardware to verify. It excludes _dq
variants because they are represented in the IR as <{2,4} x i64> when it's
actually a byte shift of the entire i{128,265}.

This also excludes _dq_bs as they aren't at all supported by the backend.
There are also no corresponding instructions in the ISA. I have no idea why
they exist...

llvm-svn: 207058

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 5d4b063d5e5..40732d2f0b9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -556,6 +556,47 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     break;
   }
 
+  // Constant fold <A x Bi> << Ci.
+  // FIXME: We don't handle _dq because it's a shift of an i128, but is
+  // represented in the IR as <2 x i64>. A per element shift is wrong.
+  case Intrinsic::x86_sse2_psll_d:
+  case Intrinsic::x86_sse2_psll_q:
+  case Intrinsic::x86_sse2_psll_w:
+  case Intrinsic::x86_sse2_pslli_d:
+  case Intrinsic::x86_sse2_pslli_q:
+  case Intrinsic::x86_sse2_pslli_w:
+  case Intrinsic::x86_avx2_psll_d:
+  case Intrinsic::x86_avx2_psll_q:
+  case Intrinsic::x86_avx2_psll_w:
+  case Intrinsic::x86_avx2_pslli_d:
+  case Intrinsic::x86_avx2_pslli_q:
+  case Intrinsic::x86_avx2_pslli_w: {
+    // Simplify if count is constant. To 0 if > BitWidth, otherwise to shl.
+    auto CDV = dyn_cast<ConstantDataVector>(II->getArgOperand(1));
+    auto CInt = dyn_cast<ConstantInt>(II->getArgOperand(1));
+    if (!CDV && !CInt)
+      break;
+    ConstantInt *Count;
+    if (CDV)
+      Count = cast<ConstantInt>(CDV->getElementAsConstant(0));
+    else
+      Count = CInt;
+
+    auto Vec = II->getArgOperand(0);
+    auto VT = cast<VectorType>(Vec->getType());
+    if (Count->getZExtValue() >
+        VT->getElementType()->getPrimitiveSizeInBits() - 1)
+      return ReplaceInstUsesWith(
+          CI, ConstantAggregateZero::get(Vec->getType()));
+    else {
+      unsigned VWidth = VT->getNumElements();
+      // Get a constant vector of the same type as the first operand.
+      auto VTCI = ConstantInt::get(VT->getElementType(), Count->getZExtValue());
+      return BinaryOperator::CreateShl(
+          Vec, Builder->CreateVectorSplat(VWidth, VTCI));
+    }
+    break;
+  }
 
   case Intrinsic::x86_sse41_pmovsxbw:
   case Intrinsic::x86_sse41_pmovsxwd: