[llvm] 676f280 - [CostModel][AArch64] Don't dereference CostTblEntry before null check.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2021-09-29T16:35:29+01:00
New Revision: 676f2809b5eb632cebac672112f42148771f4617

URL: https://github.com/llvm/llvm-project/commit/676f2809b5eb632cebac672112f42148771f4617
DIFF: https://github.com/llvm/llvm-project/commit/676f2809b5eb632cebac672112f42148771f4617.diff

LOG: [CostModel][AArch64] Don't dereference CostTblEntry before null check.

Fix static analysis warning that we check for null Entry after dereferencing it.

I don't think this can actually happen as i8/i16 should legalize to use the i32 path which should return a cost - but I'd rather play it safe that rely on an implicit type legalization.

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 87ff9393f089..1f0494621b69 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -289,13 +289,15 @@ AArch64TTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     const auto LegalisationCost = TLI->getTypeLegalizationCost(DL, RetTy);
     const auto *Entry =
         CostTableLookup(BitreverseTbl, ICA.getID(), LegalisationCost.second);
-    // Cost Model is using the legal type(i32) that i8 and i16 will be converted
-    // to +1 so that we match the actual lowering cost
-    if (TLI->getValueType(DL, RetTy, true) == MVT::i8 ||
-        TLI->getValueType(DL, RetTy, true) == MVT::i16)
-      return LegalisationCost.first * Entry->Cost + 1;
-    if (Entry)
+    if (Entry) {
+      // Cost Model is using the legal type(i32) that i8 and i16 will be
+      // converted to +1 so that we match the actual lowering cost
+      if (TLI->getValueType(DL, RetTy, true) == MVT::i8 ||
+          TLI->getValueType(DL, RetTy, true) == MVT::i16)
+        return LegalisationCost.first * Entry->Cost + 1;
+
       return LegalisationCost.first * Entry->Cost;
+    }
     break;
   }
   case Intrinsic::ctpop: {