[X86] Add constant folding for AVX512 versions of scalar floating point to integer conversion intrinsics.

Summary:
We've supported constant folding for sse versions for many years. This patch adds support for the avx512 versions including unsigned with the default rounding mode. We could probably do more with other roundings modes and SAE in the future.

The test cases are largely based on the sse.ll test cases. But I did add some test cases to ensure the unsigned versions don't accept negative values. Also checked the bounds of f64->i32 conversions to make sure unsigned has a larger positive range than signed.

Reviewers: RKSimon, spatel, chandlerc

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D50553

llvm-svn: 339529

1 files changed, 76 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index c5281c57bc1..f741f66d462 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1413,6 +1413,22 @@ bool llvm::canConstantFoldCallTo(ImmutableCallSite CS, const Function *F) {
   case Intrinsic::x86_sse2_cvtsd2si64:
   case Intrinsic::x86_sse2_cvttsd2si:
   case Intrinsic::x86_sse2_cvttsd2si64:
+  case Intrinsic::x86_avx512_vcvtss2si32:
+  case Intrinsic::x86_avx512_vcvtss2si64:
+  case Intrinsic::x86_avx512_cvttss2si:
+  case Intrinsic::x86_avx512_cvttss2si64:
+  case Intrinsic::x86_avx512_vcvtsd2si32:
+  case Intrinsic::x86_avx512_vcvtsd2si64:
+  case Intrinsic::x86_avx512_cvttsd2si:
+  case Intrinsic::x86_avx512_cvttsd2si64:
+  case Intrinsic::x86_avx512_vcvtss2usi32:
+  case Intrinsic::x86_avx512_vcvtss2usi64:
+  case Intrinsic::x86_avx512_cvttss2usi:
+  case Intrinsic::x86_avx512_cvttss2usi64:
+  case Intrinsic::x86_avx512_vcvtsd2usi32:
+  case Intrinsic::x86_avx512_vcvtsd2usi64:
+  case Intrinsic::x86_avx512_cvttsd2usi:
+  case Intrinsic::x86_avx512_cvttsd2usi64:
     return true;
   default:
     return false;
@@ -1553,7 +1569,7 @@ Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), double V,
 /// result. Returns null if the conversion cannot be performed, otherwise
 /// returns the Constant value resulting from the conversion.
 Constant *ConstantFoldSSEConvertToInt(const APFloat &Val, bool roundTowardZero,
-                                      Type *Ty) {
+                                      Type *Ty, bool IsSigned) {
   // All of these conversion intrinsics form an integer of at most 64bits.
   unsigned ResultWidth = Ty->getIntegerBitWidth();
   assert(ResultWidth <= 64 &&
@@ -1565,11 +1581,11 @@ Constant *ConstantFoldSSEConvertToInt(const APFloat &Val, bool roundTowardZero,
                                               : APFloat::rmNearestTiesToEven;
   APFloat::opStatus status =
       Val.convertToInteger(makeMutableArrayRef(UIntVal), ResultWidth,
-                           /*isSigned=*/true, mode, &isExact);
+                           IsSigned, mode, &isExact);
   if (status != APFloat::opOK &&
       (!roundTowardZero || status != APFloat::opInexact))
     return nullptr;
-  return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true);
+  return ConstantInt::get(Ty, UIntVal, IsSigned);
 }
 
 double getValueAsDouble(ConstantFP *Op) {
@@ -1849,7 +1865,8 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
         if (ConstantFP *FPOp =
                 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
           return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
-                                             /*roundTowardZero=*/false, Ty);
+                                             /*roundTowardZero=*/false, Ty,
+                                             /*IsSigned*/true);
         break;
       case Intrinsic::x86_sse_cvttss2si:
       case Intrinsic::x86_sse_cvttss2si64:
@@ -1858,7 +1875,8 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
         if (ConstantFP *FPOp =
                 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
           return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
-                                             /*roundTowardZero=*/true, Ty);
+                                             /*roundTowardZero=*/true, Ty,
+                                             /*IsSigned*/true);
         break;
       }
     }
@@ -1983,6 +2001,59 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
 
       return nullptr;
     }
+
+    // Support ConstantVector in case we have an Undef in the top.
+    if ((isa<ConstantVector>(Operands[0]) ||
+         isa<ConstantDataVector>(Operands[0])) &&
+        // Check for default rounding mode.
+        // FIXME: Support other rounding modes?
+        isa<ConstantInt>(Operands[1]) &&
+        cast<ConstantInt>(Operands[1])->getValue() == 4) {
+      auto *Op = cast<Constant>(Operands[0]);
+      switch (IntrinsicID) {
+      default: break;
+      case Intrinsic::x86_avx512_vcvtss2si32:
+      case Intrinsic::x86_avx512_vcvtss2si64:
+      case Intrinsic::x86_avx512_vcvtsd2si32:
+      case Intrinsic::x86_avx512_vcvtsd2si64:
+        if (ConstantFP *FPOp =
+                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
+          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
+                                             /*roundTowardZero=*/false, Ty,
+                                             /*IsSigned*/true);
+        break;
+      case Intrinsic::x86_avx512_vcvtss2usi32:
+      case Intrinsic::x86_avx512_vcvtss2usi64:
+      case Intrinsic::x86_avx512_vcvtsd2usi32:
+      case Intrinsic::x86_avx512_vcvtsd2usi64:
+        if (ConstantFP *FPOp =
+                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
+          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
+                                             /*roundTowardZero=*/false, Ty,
+                                             /*IsSigned*/false);
+        break;
+      case Intrinsic::x86_avx512_cvttss2si:
+      case Intrinsic::x86_avx512_cvttss2si64:
+      case Intrinsic::x86_avx512_cvttsd2si:
+      case Intrinsic::x86_avx512_cvttsd2si64:
+        if (ConstantFP *FPOp =
+                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
+          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
+                                             /*roundTowardZero=*/true, Ty,
+                                             /*IsSigned*/true);
+        break;
+      case Intrinsic::x86_avx512_cvttss2usi:
+      case Intrinsic::x86_avx512_cvttss2usi64:
+      case Intrinsic::x86_avx512_cvttsd2usi:
+      case Intrinsic::x86_avx512_cvttsd2usi64:
+        if (ConstantFP *FPOp =
+                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
+          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
+                                             /*roundTowardZero=*/true, Ty,
+                                             /*IsSigned*/false);
+        break;
+      }
+    }
     return nullptr;
   }