[clang] [llvm] [AMDGPU] Infer amdgpu-no-flat-scratch-init attribute in AMDGPUAttributor (PR #94647)

[Jun Wang via cfe-commits]

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@@ -677,6 +687,36 @@ struct AAAMDAttributesFunction : public AAAMDAttributes {
     return !A.checkForAllCallLikeInstructions(DoesNotRetrieve, *this,
                                               UsedAssumedInformation);
   }
+
+  // Returns true if FlatScratchInit is needed, i.e., no-flat-scratch-init is
+  // not to be set.
+  bool needFlatScratchInit(Attributor &A) {
+    assert(isAssumed(FLAT_SCRATCH_INIT)); // only called if the bit is still set
+
+    // This is called on each callee; false means callee shouldn't have
+    // no-flat-scratch-init.
+    auto CheckForNoFlatScratchInit = [&](Instruction &I) {
+      const auto &CB = cast<CallBase>(I);
+      const Function *Callee = CB.getCalledFunction();
+
+      if (Callee && Callee->isIntrinsic())
+        return Callee->getIntrinsicID() !=
+               Intrinsic::amdgcn_addrspacecast_nonnull;
+
+      // Return true for all other cases, including (1)inline asm, (2)direct
+      // call, and (3)indirect call with known callees. For (2) and (3)
+      // updateImpl() already checked the callees and we know their
+      // FLAT_SCRATCH_INIT bit is set.
+      return true;
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jwanggit86 wrote:

Improved a little.

https://github.com/llvm/llvm-project/pull/94647