[llvm] 513ac6e - [Attributor] Ignore illegal accesses to `null`

[Johannes Doerfert via llvm-commits]

Author: Johannes Doerfert
Date: 2020-05-10T19:06:10-05:00
New Revision: 513ac6e9b045dd2d5e0d1a5e221380cfb999676a

URL: https://github.com/llvm/llvm-project/commit/513ac6e9b045dd2d5e0d1a5e221380cfb999676a
DIFF: https://github.com/llvm/llvm-project/commit/513ac6e9b045dd2d5e0d1a5e221380cfb999676a.diff

LOG: [Attributor] Ignore illegal accesses to `null`

When we categorize a pointer value we bailed at `null` before. If we
know `null` is not a valid memory location we can ignore it as there
won't be an access at all.

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/AttributorAttributes.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index b3f656da5e33..26196f0a2416 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -6229,9 +6229,13 @@ void AAMemoryLocationImpl::categorizePtrValue(
         MLK = NO_GLOBAL_INTERNAL_MEM;
       else
         MLK = NO_GLOBAL_EXTERNAL_MEM;
-    } else if (isa<AllocaInst>(V))
+    } else if (isa<ConstantPointerNull>(V) &&
+               !NullPointerIsDefined(getAssociatedFunction(),
+                                     V.getType()->getPointerAddressSpace())) {
+      return true;
+    } else if (isa<AllocaInst>(V)) {
       MLK = NO_LOCAL_MEM;
-    else if (const auto *CB = dyn_cast<CallBase>(&V)) {
+    } else if (const auto *CB = dyn_cast<CallBase>(&V)) {
       const auto &NoAliasAA =
           A.getAAFor<AANoAlias>(*this, IRPosition::callsite_returned(*CB));
       if (NoAliasAA.isAssumedNoAlias())