[llvm] [InstCombine] Add combines/simplifications for `llvm.ptrmask` (PR #67166)

[Nikita Popov via llvm-commits]

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@@ -1985,6 +1985,28 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
                                     {InnerPtr, NewMask}));
       }
     }
+    bool Changed = false;
+    KnownBits Known = computeKnownBits(II, /*Depth*/ 0, II);
+    // See if we can deduce non-null.
+    if (!CI.hasRetAttr(Attribute::NonNull) &&
+        (Known.isNonZero() ||
+         isKnownNonZero(II, DL, /*Depth*/ 0, &AC, II, &DT))) {
+      CI.addRetAttr(Attribute::NonNull);
+      Changed = true;
+    }
+
+    // Known bits will capture if we had alignment information assosiated with
+    // the pointer argument.
+    if (Known.countMinTrailingZeros() > Log2(CI.getRetAlign().valueOrOne())) {
+      if (CI.hasRetAttr(Attribute::Alignment))
+        CI.removeRetAttr(Attribute::Alignment);
+      CI.addRetAttr(
+          Attribute::get(CI.getContext(), Attribute::Alignment,
+                         uint64_t(1) << Known.countMinTrailingZeros()));
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nikic wrote:

Attribute::getWithAlignment(). Also you need to protect against MaximumAlignment here.

https://github.com/llvm/llvm-project/pull/67166