================
@@ -205,6 +231,26 @@ class TypeHashMode : public ModeBase {
}
};
+/// Implementation for TokenMode::TypeHashPointerSplit.
+class TypeHashPointerSplitMode : public TypeHashMode {
+public:
+ using TypeHashMode::TypeHashMode;
+
+ uint64_t operator()(const CallBase &CB, OptimizationRemarkEmitter &ORE) {
+ if (MaxTokens == 1)
+ return 0;
+ const uint64_t HalfTokens =
+ (MaxTokens ? MaxTokens : std::numeric_limits<uint64_t>::max()) / 2;
+ const auto [N, H] = getHash(CB, ORE);
+ if (!N)
+ return H; // fallback token
----------------
melver wrote:
It goes into the pointer-less bucket by default:
```
--- a/llvm/lib/Transforms/Instrumentation/AllocToken.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AllocToken.cpp
@@ -242,8 +242,12 @@ public:
const uint64_t HalfTokens =
(MaxTokens ? MaxTokens : std::numeric_limits<uint64_t>::max()) / 2;
const auto [N, H] = getHash(CB, ORE);
- if (!N)
- return H; // fallback token
+ if (!N) {
+ // Pick the fallback token (ClFallbackToken), which by default is 0,
+ // meaning it'll fall into the pointer-less bucket. Override by setting
+ // -alloc-token-fallback if that is the wrong choice.
+ return H;
+ }
```
Advanced users could e.g. set -alloc-token-fallback to some bucket outside the
range of normal buckets, but I have no intuition if that's a good or bad choice
if this is used for heap hardening strategies. So I wouldn't want to expose
this as a standard "frontend option" either.
E.g. we're having discussions if we should pick the pointer-containing bucket
as the default for fallbacks. The intuition behind that is to "protect
pointer-containing allocations" from (more likely) buggy plain data/buffer
allocations, but at the same time we could stick a plain buffer allocation
(where inference failed) into the fallback which makes the whole point moot.
Ideally we end up with few/no fallback cases.
https://github.com/llvm/llvm-project/pull/156840
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