[InstCombine][SSE] Demanded vector elements for scalar intrinsics (Part 2 of 2)

Split from D17490. This patch improves support for determining the demanded vector elements through SSE scalar intrinsics:

1 - demanded vector element support for unary and some extra binary scalar intrinsics (RCP/RSQRT/SQRT/FRCZ and ADD/CMP/DIV/ROUND).

2 - addss/addsd get simplified to a fadd call if we aren't interested in the pass through elements

3 - if we don't need the lowest element of a scalar operation then just use the first argument (the pass through elements) directly

We can add support for propagating demanded elements through any equivalent packed SSE intrinsics in a future patch (these wouldn't use the pass through patterns).

Differential Revision: http://reviews.llvm.org/D19318

llvm-svn: 267357

1 files changed, 38 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index ef5be69bf8a..da2617c57cf 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1179,16 +1179,41 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
     switch (II->getIntrinsicID()) {
     default: break;
 
+    // Unary vector operations that work column-wise.
+    case Intrinsic::x86_sse_rcp_ss:
+    case Intrinsic::x86_sse_rsqrt_ss:
+    case Intrinsic::x86_sse_sqrt_ss:
+    case Intrinsic::x86_sse2_sqrt_sd:
+    case Intrinsic::x86_xop_vfrcz_ss:
+    case Intrinsic::x86_xop_vfrcz_sd:
+      TmpV = SimplifyDemandedVectorElts(II->getArgOperand(0), DemandedElts,
+                                        UndefElts, Depth + 1);
+      if (TmpV) { II->setArgOperand(0, TmpV); MadeChange = true; }
+
+      // If lowest element of a scalar op isn't used then use Arg0.
+      if (DemandedElts.getLoBits(1) != 1)
+        return II->getArgOperand(0);
+      // TODO: If only low elt lower SQRT to FSQRT (with rounding/exceptions checks).
+      break;
+
     // Binary vector operations that work column-wise.  A dest element is a
     // function of the corresponding input elements from the two inputs.
+    case Intrinsic::x86_sse_add_ss:
     case Intrinsic::x86_sse_sub_ss:
     case Intrinsic::x86_sse_mul_ss:
+    case Intrinsic::x86_sse_div_ss:
     case Intrinsic::x86_sse_min_ss:
     case Intrinsic::x86_sse_max_ss:
+    case Intrinsic::x86_sse_cmp_ss:
+    case Intrinsic::x86_sse2_add_sd:
     case Intrinsic::x86_sse2_sub_sd:
     case Intrinsic::x86_sse2_mul_sd:
+    case Intrinsic::x86_sse2_div_sd:
     case Intrinsic::x86_sse2_min_sd:
     case Intrinsic::x86_sse2_max_sd:
+    case Intrinsic::x86_sse2_cmp_sd:
+    case Intrinsic::x86_sse41_round_ss:
+    case Intrinsic::x86_sse41_round_sd:
       TmpV = SimplifyDemandedVectorElts(II->getArgOperand(0), DemandedElts,
                                         UndefElts, Depth + 1);
       if (TmpV) { II->setArgOperand(0, TmpV); MadeChange = true; }
@@ -1201,11 +1226,14 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
       if (DemandedElts == 1) {
         switch (II->getIntrinsicID()) {
         default: break;
+        case Intrinsic::x86_sse_add_ss:
         case Intrinsic::x86_sse_sub_ss:
         case Intrinsic::x86_sse_mul_ss:
+        case Intrinsic::x86_sse2_add_sd:
         case Intrinsic::x86_sse2_sub_sd:
         case Intrinsic::x86_sse2_mul_sd:
-          // TODO: Lower MIN/MAX/ABS/etc
+          // TODO: Lower MIN/MAX/etc.
+          // TODO: Lower DIV (with rounding/exceptions checks).
           Value *LHS = II->getArgOperand(0);
           Value *RHS = II->getArgOperand(1);
           // Extract the element as scalars.
@@ -1216,6 +1244,11 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
 
           switch (II->getIntrinsicID()) {
           default: llvm_unreachable("Case stmts out of sync!");
+          case Intrinsic::x86_sse_add_ss:
+          case Intrinsic::x86_sse2_add_sd:
+            TmpV = InsertNewInstWith(BinaryOperator::CreateFAdd(LHS, RHS,
+                                                        II->getName()), *II);
+            break;
           case Intrinsic::x86_sse_sub_ss:
           case Intrinsic::x86_sse2_sub_sd:
             TmpV = InsertNewInstWith(BinaryOperator::CreateFSub(LHS, RHS,
@@ -1238,6 +1271,10 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
         }
       }
 
+      // If lowest element of a scalar op isn't used then use Arg0.
+      if (DemandedElts.getLoBits(1) != 1)
+        return II->getArgOperand(0);
+
       // Output elements are undefined if both are undefined.  Consider things
       // like undef&0.  The result is known zero, not undef.
       UndefElts &= UndefElts2;