[NVPTX] Sync generation of parameter names in a function signature with the function body.

[pavelkopyl]

Summary

This fixes parameter names mismatch in anonymous functions.

[tra]

Thank you for the patch. I'm OK with the fix in principle, but would like to check if we could make parameter name generation common for both function signature and the parameter symbol.

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

2624

While this does seem to produce correct argument name, at least for the test example, I'm not convinced it's the best way to handle this. The issue is that we're still generating parameter symbol name here separately from where it gets generated for the function signature. Off the top of my head I do not recall where it happens and I didn't have time to track it down yet.

We should attempt to make sure that the name is guaranteed to be generated using the same algorithm. E.g. via a common helper function.

llvm/test/CodeGen/NVPTX/anonymous-fn-param.ll

4

The patch description and the test should be a bit more specific describing what the problem is.

AFAICT, the problem is that there's currently a mismatch between the parameter name we generate in the function signature (__unnamed_1_param_0) and the name we use when we refer to the parameter in the body of the function (_param_0). https://godbolt.org/z/dMEKe1anG

[pavelkopyl]

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

2624

Thank you for the review. I slightly refactored the code that generates param names to have all in one place.

llvm/test/CodeGen/NVPTX/anonymous-fn-param.ll

4

Done.

[pavelkopyl]

• Rebase
• Refactor the code that generates param names to have all in one place.

[tra]

Nice! I like that there's just one way to determine parameter name now.

llvm/test/CodeGen/NVPTX/anonymous-fn-param.ll

12–14

I'd move it down to the second function. When possible, checks should be placed close to the code that we're checking.

[pavelkopyl]

• Update the test according to review notes.

llvm/test/CodeGen/NVPTX/anonymous-fn-param.ll

12–14

Done.

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

 // Name of the symbol is composed from its index and the function name.
 // Negative index corresponds to special parameter (unsized array) used for
 // passing variable arguments.
 SDValue NVPTXTargetLowering::getParamSymbol(SelectionDAG &DAG, int idx,
                                             EVT v) const {
   std::string ParamSym;
   raw_string_ostream ParamStr(ParamSym);
 
-  ParamStr << DAG.getMachineFunction().getName();
+  if (StringRef FnName = DAG.getMachineFunction().getName(); !FnName.empty()) {
+    ParamStr << FnName;
+  } else {
+    SmallString<128> NameBuf;
+    getTargetMachine().getObjFileLowering()->getNameWithPrefix(
+        NameBuf, &DAG.getMachineFunction().getFunction(), getTargetMachine());
+    ParamStr << NameBuf;
+  }
 
   if (idx < 0)
     ParamStr << "_vararg";
   else
     ParamStr << "_param_" << idx;
 
   StringRef SavedStr =
     nvTM->getStrPool().save(ParamSym);

llvm/test/CodeGen/NVPTX/anonymous-fn-param.ll

+; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 | FileCheck %s
+; RUN: %if ptxas %{ llc < %s -march=nvptx64 -mcpu=sm_20 | %ptxas-verify %}
+
+; CHECK:      .func (.param .b32 func_retval0) __unnamed_1(
+; CHECK-NEXT: .param .b32 __unnamed_1_param_0
+; CHECK:      ld.param.u32 {{%r[0-9]+}}, [__unnamed_1_param_0];
+
+; CHECK:      .func (.param .b32 func_retval0) __unnamed_2(
+; CHECK-NEXT: .param .b32 __unnamed_2_param_0
+; CHECK:      ld.param.u32 {{%r[0-9]+}}, [__unnamed_2_param_0];
+
+define internal i32 @0(i32 %a) {
+entry:
+  %r = add i32 %a, 1
+  ret i32 %r
+}
+
+define internal i32 @1(i32 %a) {
+entry:
+  %r = add i32 %a, 1
+  ret i32 %r
+}