From f0aae37e1d58cc08f16d642c80e096f81de0a2ff Mon Sep 17 00:00:00 2001
From: Christopher Tetreault <ctetreau@quicinc.com>
Date: Tue, 16 Jun 2020 13:19:15 -0700
Subject: [PATCH] [NFC] Bail out for scalable vectors before calling
 getNumElements

Summary:
Move the bail out logic to before constructing the Result and Lane
vectors. This is both potentially faster, and avoids calling
getNumElements on a potentially scalable vector

Reviewers: efriedma, sunfish, chandlerc, c-rhodes, fpetrogalli

Reviewed By: fpetrogalli

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81619
---
 lib/Analysis/ConstantFolding.cpp | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 67591de756c..76e7b2906c9 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -2689,24 +2689,26 @@ static Constant *ConstantFoldVectorCall(StringRef Name,
                                         const DataLayout &DL,
                                         const TargetLibraryInfo *TLI,
                                         const CallBase *Call) {
-  SmallVector<Constant *, 4> Result(VTy->getNumElements());
-  SmallVector<Constant *, 4> Lane(Operands.size());
-  Type *Ty = VTy->getElementType();
-
   // Do not iterate on scalable vector. The number of elements is unknown at
   // compile-time.
   if (isa<ScalableVectorType>(VTy))
     return nullptr;
 
+  auto *FVTy = cast<FixedVectorType>(VTy);
+
+  SmallVector<Constant *, 4> Result(FVTy->getNumElements());
+  SmallVector<Constant *, 4> Lane(Operands.size());
+  Type *Ty = FVTy->getElementType();
+
   if (IntrinsicID == Intrinsic::masked_load) {
     auto *SrcPtr = Operands[0];
     auto *Mask = Operands[2];
     auto *Passthru = Operands[3];
 
-    Constant *VecData = ConstantFoldLoadFromConstPtr(SrcPtr, VTy, DL);
+    Constant *VecData = ConstantFoldLoadFromConstPtr(SrcPtr, FVTy, DL);
 
     SmallVector<Constant *, 32> NewElements;
-    for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
+    for (unsigned I = 0, E = FVTy->getNumElements(); I != E; ++I) {
       auto *MaskElt = Mask->getAggregateElement(I);
       if (!MaskElt)
         break;
@@ -2732,12 +2734,12 @@ static Constant *ConstantFoldVectorCall(StringRef Name,
         return nullptr;
       }
     }
-    if (NewElements.size() != VTy->getNumElements())
+    if (NewElements.size() != FVTy->getNumElements())
       return nullptr;
     return ConstantVector::get(NewElements);
   }
 
-  for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
+  for (unsigned I = 0, E = FVTy->getNumElements(); I != E; ++I) {
     // Gather a column of constants.
     for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) {
       // Some intrinsics use a scalar type for certain arguments.