[InstCombine] SSE/SSE2 (u)comiss/(u)comisd comparison intrinsics only use the lowest vector element

llvm-svn: 261460

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 2904da01b0e..0f53711d937 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1194,6 +1194,46 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     break;
   }
 
+  case Intrinsic::x86_sse_comieq_ss:
+  case Intrinsic::x86_sse_comige_ss:
+  case Intrinsic::x86_sse_comigt_ss:
+  case Intrinsic::x86_sse_comile_ss:
+  case Intrinsic::x86_sse_comilt_ss:
+  case Intrinsic::x86_sse_comineq_ss:
+  case Intrinsic::x86_sse_ucomieq_ss:
+  case Intrinsic::x86_sse_ucomige_ss:
+  case Intrinsic::x86_sse_ucomigt_ss:
+  case Intrinsic::x86_sse_ucomile_ss:
+  case Intrinsic::x86_sse_ucomilt_ss:
+  case Intrinsic::x86_sse_ucomineq_ss:
+  case Intrinsic::x86_sse2_comieq_sd:
+  case Intrinsic::x86_sse2_comige_sd:
+  case Intrinsic::x86_sse2_comigt_sd:
+  case Intrinsic::x86_sse2_comile_sd:
+  case Intrinsic::x86_sse2_comilt_sd:
+  case Intrinsic::x86_sse2_comineq_sd:
+  case Intrinsic::x86_sse2_ucomieq_sd:
+  case Intrinsic::x86_sse2_ucomige_sd:
+  case Intrinsic::x86_sse2_ucomigt_sd:
+  case Intrinsic::x86_sse2_ucomile_sd:
+  case Intrinsic::x86_sse2_ucomilt_sd:
+  case Intrinsic::x86_sse2_ucomineq_sd: {
+    // These intrinsics only demand the 0th element of their input vectors. If
+    // we can simplify the input based on that, do so now.
+    Value *Arg0 = II->getArgOperand(0);
+    Value *Arg1 = II->getArgOperand(1);
+    unsigned VWidth = Arg0->getType()->getVectorNumElements();
+    if (Value *V = SimplifyDemandedVectorEltsLow(Arg0, VWidth, 1)) {
+      II->setArgOperand(0, V);
+      return II;
+    }
+    if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, 1)) {
+      II->setArgOperand(1, V);
+      return II;
+    }
+    break;
+  }
+
   // Constant fold ashr( <A x Bi>, Ci ).
   // Constant fold lshr( <A x Bi>, Ci ).
   // Constant fold shl( <A x Bi>, Ci ).