[llvm] [InlineCost] Cache collectEphemeralValues() to save compile time (PR #130210)

[Nikita Popov via llvm-commits]

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@@ -2781,11 +2790,15 @@ InlineResult CallAnalyzer::analyze() {
   NumConstantOffsetPtrArgs = ConstantOffsetPtrs.size();
   NumAllocaArgs = SROAArgValues.size();
 
-  // FIXME: If a caller has multiple calls to a callee, we end up recomputing
-  // the ephemeral values multiple times (and they're completely determined by
-  // the callee, so this is purely duplicate work).
-  SmallPtrSet<const Value *, 32> EphValues;
-  CodeMetrics::collectEphemeralValues(&F, &GetAssumptionCache(F), EphValues);
+  // Collecting the ephemeral values of `F` can be expensive, so use the
+  // ephemeral values cache if available.
+  SmallPtrSet<const Value *, 32> EphValuesStorage;
+  const SmallPtrSetImpl<const Value *> *EphValues = &EphValuesStorage;
+  auto &AC = GetAssumptionCache(F);
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nikic wrote:

Can move the GetAssumptionCache() into the branch that uses it.

https://github.com/llvm/llvm-project/pull/130210