[flang][debug] Use PROGRAM name for main function name (#111022)

For example, in

        PROGRAM test_program
          ...
        END PROGRAM

This allows a user to break on the main function with `break
test_program`. This matches what classic flang and gfortran do.

Author: tblah

flang/lib/Optimizer/Transforms/AddDebugInfo.cpp

@@ -18,6 +18,7 @@
 #include "flang/Optimizer/CodeGen/CGOps.h"
 #include "flang/Optimizer/Dialect/FIRDialect.h"
 #include "flang/Optimizer/Dialect/FIROps.h"
+#include "flang/Optimizer/Dialect/FIROpsSupport.h"
 #include "flang/Optimizer/Dialect/FIRType.h"
 #include "flang/Optimizer/Dialect/Support/FIRContext.h"
 #include "flang/Optimizer/Support/InternalNames.h"
@@ -265,6 +266,14 @@ void AddDebugInfoPass::handleFuncOp(mlir::func::FuncOp funcOp,
   auto result = fir::NameUniquer::deconstruct(funcName);
   funcName = mlir::StringAttr::get(context, result.second.name);
 
+  // try to use a better function name than _QQmain for the program statement
+  if (funcName == fir::NameUniquer::doProgramEntry()) {
+    mlir::StringAttr bindcName =
+        funcOp->getAttrOfType<mlir::StringAttr>(fir::getSymbolAttrName());
+    if (bindcName)
+      funcName = bindcName;
+  }
+
   llvm::SmallVector<mlir::LLVM::DITypeAttr> types;
   for (auto resTy : funcOp.getResultTypes()) {
     auto tyAttr =

flang/test/Integration/debug-local-var-2.f90

@@ -53,7 +53,7 @@
 ! BOTH-LABEL: }
 
 program mn
-! BOTH-DAG: ![[MAIN:.*]] = distinct !DISubprogram(name: "_QQmain", {{.*}})
+! BOTH-DAG: ![[MAIN:.*]] = distinct !DISubprogram(name: "mn", {{.*}})
 
 ! BOTH-DAG: ![[TYI32:.*]] = !DIBasicType(name: "integer", size: 32, encoding: DW_ATE_signed)
 ! BOTH-DAG: ![[TYI64:.*]] = !DIBasicType(name: "integer", size: 64, encoding: DW_ATE_signed)

flang/test/Transforms/debug-fn-info.fir

@@ -76,7 +76,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
 // CHECK: #[[TY3:.*]] = #llvm.di_subroutine_type<callingConvention = DW_CC_normal, types = #di_null_type, #[[INT4]]>
 
 // Line numbers should match the number in corresponding loc entry.
-// CHECK: #llvm.di_subprogram<{{.*}}name = "_QQmain", linkageName = "_QQmain", file = {{.*}}, line = 15, scopeLine = 15, subprogramFlags = Definition, type = #[[TY0]]>
+// CHECK: #llvm.di_subprogram<{{.*}}name = "mn", linkageName = "_QQmain", file = {{.*}}, line = 15, scopeLine = 15, subprogramFlags = Definition, type = #[[TY0]]>
 // CHECK: #llvm.di_subprogram<{{.*}}name = "fn1", linkageName = "_QFPfn1", file = {{.*}}, line = 26, scopeLine = 26, subprogramFlags = Definition, type = #[[TY1]]>
 // CHECK: #llvm.di_subprogram<{{.*}}name = "fn2", linkageName = "_QFPfn2", file = {{.*}}, line = 43, scopeLine = 43, subprogramFlags = Definition, type = #[[TY2]]>
 // CHECK: #llvm.di_subprogram<{{.*}}name = "fn3", linkageName = "_QFPfn3", file = {{.*}}, line = 53, scopeLine = 53, subprogramFlags = Definition, type = #[[TY3]]>

flang/test/Transforms/debug-local-global-storage-1.fir

@@ -44,7 +44,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<i64, dense<64> :
 
 // CHECK-DAG: #[[CU:.*]] = #llvm.di_compile_unit<{{.*}}>
 // CHECK-DAG: #[[MOD:.*]] = #llvm.di_module<{{.*}}scope = #[[CU]]{{.*}}name = "example"{{.*}}>
-// CHECK-DAG: #[[SP:.*]] = #llvm.di_subprogram<{{.*}}name = "_QQmain"{{.*}}>
+// CHECK-DAG: #[[SP:.*]] = #llvm.di_subprogram<{{.*}}name = "test"{{.*}}>
 // CHECK-DAG: #[[MOD_SP:.*]] = #llvm.di_subprogram<{{.*}}name = "mod_sub"{{.*}}retainedNodes = {{.*}}>
 // CHECK-DAG: #llvm.di_global_variable<scope = #[[SP]], name = "arr"{{.*}}line = 22{{.*}}>
 // CHECK-DAG: #llvm.di_global_variable<scope = #[[SP]], name = "s"{{.*}}line = 23{{.*}}>

flang/test/Transforms/debug-local-var.fir

@@ -77,7 +77,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
 // CHECK-DAG: #[[LOG1:.*]] = #llvm.di_basic_type<tag = DW_TAG_base_type, name = "logical", sizeInBits = 8, encoding = DW_ATE_boolean>
 // CHECK-DAG: #[[REAL4:.*]] = #llvm.di_basic_type<tag = DW_TAG_base_type, name = "real", sizeInBits = 32, encoding = DW_ATE_float>
 // CHECK-DAG: #[[LOG4:.*]] = #llvm.di_basic_type<tag = DW_TAG_base_type, name = "logical", sizeInBits = 32, encoding = DW_ATE_boolean>
-// CHECK-DAG: #[[MAIN:.*]] = #llvm.di_subprogram<{{.*}}name = "_QQmain"{{.*}}>
+// CHECK-DAG: #[[MAIN:.*]] = #llvm.di_subprogram<{{.*}}name = "mn"{{.*}}>
 // CHECK-DAG: #[[FN1:.*]] = #llvm.di_subprogram<{{.*}}name = "fn1"{{.*}}>
 // CHECK-DAG: #[[FN2:.*]] = #llvm.di_subprogram<{{.*}}name = "fn2"{{.*}}>