[PATCH] D65246: [WebAssembly] Do not emit tail calls with return type mismatch

[Heejin Ahn via Phabricator via llvm-commits]

aheejin added inline comments.


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Comment at: llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp:649
+    bool MustTail = CLI.CS && CLI.CS.isMustTailCall();
+    if (Subtarget->hasTailCall() && !CLI.IsVarArg) {
+      // Do not tail call unless caller and callee return types match
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Would we need a test case for vararg too?


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Comment at: llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp:677
+    }
   }
 
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Should we document about these restrictions (such as no vararg) [[ https://llvm.org/docs/CodeGenerator.html#tail-call-optimization | here ]] too, like other platforms?


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Comment at: llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp:238
+            valTypesFromMVTs(CallerRetTys, Returns);
+          }
+
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Why should we do this? Is the return type of the tail-called function different from that of the caller? If so, wouldn't we have already disabled tail calling in ISelLowering as you did above?


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Comment at: llvm/test/CodeGen/WebAssembly/tailcall.ll:215
+; Check that the signatures generated for external indirectly
+; return-called functions include the proper return types
+
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I'm not sure what this test is trying to test..?


Repository:
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  https://reviews.llvm.org/D65246/new/

https://reviews.llvm.org/D65246