clang: Improve errors for DiagnosticInfoResourceLimit

Print source location info and demangle the name, compared
to the default behavior.

Several observations:

1. Specially handling this seems to give source locations
without enabling debug info, and also gives columns compared
to the backend diagnostic.

2. We're duplicating diagnostic effort in DiagnosticInfo
and clang. This feels wrong, but clang can demangle and I guess
have better debug info available? Should clang really have any of this
code? For the purposes of this diagnostic, the important piece
is just reading the source location out of the llvm::Function.

3. lld is not duplicating the same effort as clang with LTO, and
just directly printing the DiagnosticInfo as-is. e.g.

  $ clang -fgpu-rdc
	lld: error: local memory (480000) exceeds limit (65536) in function '_Z12use_huge_ldsIiEvv'
	lld: error: local memory (960000) exceeds limit (65536) in function '_Z12use_huge_ldsIdEvv'

  $ clang -fno-gpu-rdc
	backend-resource-limit-diagnostics.hip:8:17: error: local memory (480000) exceeds limit (65536) in 'void use_huge_lds<int>()'
	__global__ void use_huge_lds() {
                ^
	backend-resource-limit-diagnostics.hip:8:17: error: local memory (960000) exceeds limit (65536) in 'void use_huge_lds<double>()'
	2 errors generated when compiling for gfx90a.

4. Backend errors are not observed with -save-temps and -fno-gpu-rdc or -flto,
and the compile incorrectly succeeds.

5. The backend version prints error: <location info>; clang prints <location info>: error:

6. -emit-codegen-only is totally broken for AMDGPU. MC
gets a null target streamer. I do not understand why this
is a thing. This just creates a horrible edge case.
Just work around this by emitting actual code instead of blocking
this patch.

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -35,6 +35,11 @@ def note_fe_backend_frame_larger_than: Note<"%0">, BackendInfo;
 
 def warn_fe_backend_plugin: Warning<"%0">, BackendInfo, InGroup<BackendPlugin>;
 def err_fe_backend_plugin: Error<"%0">, BackendInfo;
+
+def warn_fe_backend_resource_limit: Warning<"%0 (%1) exceeds limit (%2) in '%3'">, BackendInfo, InGroup<BackendPlugin>;
+def err_fe_backend_resource_limit: Error<"%0 (%1) exceeds limit (%2) in '%3'">, BackendInfo;
+def note_fe_backend_resource_limit: Note<"%0 (%1) exceeds limit (%2) in '%3'">, BackendInfo;
+
 def remark_fe_backend_plugin: Remark<"%0">, BackendInfo, InGroup<RemarkBackendPlugin>;
 def note_fe_backend_plugin: Note<"%0">, BackendInfo;
 

clang/lib/CodeGen/CodeGenAction.cpp

@@ -435,6 +435,11 @@ namespace clang {
     /// \return True if the diagnostic has been successfully reported, false
     /// otherwise.
     bool StackSizeDiagHandler(const llvm::DiagnosticInfoStackSize &D);
+    /// Specialized handler for ResourceLimit diagnostic.
+    /// \return True if the diagnostic has been successfully reported, false
+    /// otherwise.
+    bool ResourceLimitDiagHandler(const llvm::DiagnosticInfoResourceLimit &D);
+
     /// Specialized handler for unsupported backend feature diagnostic.
     void UnsupportedDiagHandler(const llvm::DiagnosticInfoUnsupported &D);
     /// Specialized handlers for optimization remarks.
@@ -631,6 +636,20 @@ BackendConsumer::StackSizeDiagHandler(const llvm::DiagnosticInfoStackSize &D) {
   return true;
 }
 
+bool BackendConsumer::ResourceLimitDiagHandler(
+    const llvm::DiagnosticInfoResourceLimit &D) {
+  auto Loc = getFunctionSourceLocation(D.getFunction());
+  if (!Loc)
+    return false;
+  unsigned DiagID = diag::err_fe_backend_resource_limit;
+  ComputeDiagID(D.getSeverity(), backend_resource_limit, DiagID);
+
+  Diags.Report(*Loc, DiagID)
+      << D.getResourceName() << D.getResourceSize() << D.getResourceLimit()
+      << llvm::demangle(D.getFunction().getName().str());
+  return true;
+}
+
 const FullSourceLoc BackendConsumer::getBestLocationFromDebugLoc(
     const llvm::DiagnosticInfoWithLocationBase &D, bool &BadDebugInfo,
     StringRef &Filename, unsigned &Line, unsigned &Column) const {
@@ -874,6 +893,11 @@ void BackendConsumer::DiagnosticHandlerImpl(const DiagnosticInfo &DI) {
       return;
     ComputeDiagID(Severity, backend_frame_larger_than, DiagID);
     break;
+  case llvm::DK_ResourceLimit:
+    if (ResourceLimitDiagHandler(cast<DiagnosticInfoResourceLimit>(DI)))
+      return;
+    ComputeDiagID(Severity, backend_resource_limit, DiagID);
+    break;
   case DK_Linker:
     ComputeDiagID(Severity, linking_module, DiagID);
     break;

clang/test/Misc/backend-resource-limit-diagnostics.cl

@@ -1,7 +1,7 @@
 // REQUIRES: amdgpu-registered-target
-// RUN: not %clang_cc1 -debug-info-kind=standalone -x cl -emit-codegen-only -triple=amdgcn-- < %s 2>&1 | FileCheck %s
+// RUN: not %clang_cc1 -x cl -emit-codegen-only -triple=amdgcn-- < %s 2>&1 | FileCheck %s
 
-// CHECK: error: <stdin>:[[@LINE+1]]:0: local memory (480000) exceeds limit (32768) in function 'use_huge_lds'
+// CHECK: <stdin>:[[@LINE+1]]:13: error: local memory (480000) exceeds limit (32768) in 'use_huge_lds'
 kernel void use_huge_lds() {
     volatile local int huge[120000];
     huge[0] = 2;

clang/test/Misc/backend-resource-limit-diagnostics.hip

@@ -10,10 +10,10 @@ __global__ void use_huge_lds() {
   huge[0] = 2;
 }
 
-// CHECK: error: <stdin>:[[#@LINE-5]]:0: local memory (480000) exceeds limit (65536) in function '_Z12use_huge_ldsIiEvv'
+// CHECK: <stdin>:[[@LINE-5]]:17: error: local memory (480000) exceeds limit (65536) in 'void use_huge_lds<int>()'
 template
 __global__ void use_huge_lds<int>();
 
-// CHECK: error: <stdin>:[[#@LINE-9]]:0: local memory (960000) exceeds limit (65536) in function '_Z12use_huge_ldsIdEvv'
+// CHECK: <stdin>:[[@LINE-9]]:17: error: local memory (960000) exceeds limit (65536) in 'void use_huge_lds<double>()'
 template
 __global__ void use_huge_lds<double>();