[clang] 80a4e6f - [Driver] Error for -gsplit-dwarf with RISC-V linker relaxation

[Fangrui Song via cfe-commits]

Author: Fangrui Song
Date: 2022-07-22T17:16:41-07:00
New Revision: 80a4e6fd31a06143b83947785ea3bd5c04344ea6

URL: https://github.com/llvm/llvm-project/commit/80a4e6fd31a06143b83947785ea3bd5c04344ea6
DIFF: https://github.com/llvm/llvm-project/commit/80a4e6fd31a06143b83947785ea3bd5c04344ea6.diff

LOG: [Driver] Error for -gsplit-dwarf with RISC-V linker relaxation

-gsplit-dwarf produces a .dwo file which will not be processed by the linker. If
.dwo files contain relocations, they will not be resolved. Therefore the
practice is that .dwo files do not contain relocations.

Address ranges and location description need to use forms/entry kinds indexing
into .debug_addr (DW_FORM_addrx/DW_RLE_startx_endx/etc), which is currently not
implemented.

There is a difficult-to-read MC error with -gsplit-dwarf with RISC-V for both -mrelax and -mno-relax.
```
% clang --target=riscv64-linux-gnu -g -gsplit-dwarf -c a.c
error: A dwo section may not contain relocations
```

We expect to fix -mno-relax soon, so report a driver error for -mrelax for now.

Link: https://github.com/llvm/llvm-project/issues/56642

Reviewed By: compnerd, kito-cheng

Differential Revision: https://reviews.llvm.org/D130190

Added: 
    

Modified: 
    clang/include/clang/Basic/DiagnosticDriverKinds.td
    clang/lib/Driver/ToolChains/Arch/RISCV.cpp
    clang/lib/Driver/ToolChains/Clang.cpp
    clang/lib/Driver/ToolChains/Clang.h
    clang/test/Driver/riscv-features.c

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 3c5f7e087de85..2f600d28fea0c 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -682,4 +682,7 @@ def err_drv_invalid_empty_dxil_validator_version : Error<
 def warn_drv_sarif_format_unstable : Warning<
   "diagnostic formatting in SARIF mode is currently unstable">,
   InGroup<DiagGroup<"sarif-format-unstable">>;
+
+def err_drv_riscv_unsupported_with_linker_relaxation : Error<
+  "%0 is unsupported with RISC-V linker relaxation (-mrelax)">;
 }

diff  --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
index 8a8ed20986c57..de6e045a9447f 100644
--- a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "RISCV.h"
+#include "../Clang.h"
 #include "ToolChains/CommonArgs.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Driver/Driver.h"
@@ -137,10 +138,17 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
     Features.push_back("+reserve-x31");
 
   // -mrelax is default, unless -mno-relax is specified.
-  if (Args.hasFlag(options::OPT_mrelax, options::OPT_mno_relax, true))
+  if (Args.hasFlag(options::OPT_mrelax, options::OPT_mno_relax, true)) {
     Features.push_back("+relax");
-  else
+    // -gsplit-dwarf -mrelax requires DW_AT_high_pc/DW_AT_ranges/... indexing
+    // into .debug_addr, which is currently not implemented.
+    Arg *A;
+    if (getDebugFissionKind(D, Args, A) != DwarfFissionKind::None)
+      D.Diag(clang::diag::err_drv_riscv_unsupported_with_linker_relaxation)
+          << A->getAsString(Args);
+  } else {
     Features.push_back("-relax");
+  }
 
   // GCC Compatibility: -mno-save-restore is default, unless -msave-restore is
   // specified.

diff  --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 33e3fe267c239..3044c2d92d21f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4034,9 +4034,7 @@ static void RenderDiagnosticsOptions(const Driver &D, const ArgList &Args,
                      options::OPT_fno_spell_checking);
 }
 
-enum class DwarfFissionKind { None, Split, Single };
-
-static DwarfFissionKind getDebugFissionKind(const Driver &D,
+DwarfFissionKind tools::getDebugFissionKind(const Driver &D,
                                             const ArgList &Args, Arg *&Arg) {
   Arg = Args.getLastArg(options::OPT_gsplit_dwarf, options::OPT_gsplit_dwarf_EQ,
                         options::OPT_gno_split_dwarf);

diff  --git a/clang/lib/Driver/ToolChains/Clang.h b/clang/lib/Driver/ToolChains/Clang.h
index 37263efd57a5e..5209c6687599b 100644
--- a/clang/lib/Driver/ToolChains/Clang.h
+++ b/clang/lib/Driver/ToolChains/Clang.h
@@ -198,6 +198,12 @@ class LLVM_LIBRARY_VISIBILITY LinkerWrapper final : public Tool {
                     const char *LinkingOutput) const override;
 };
 
+enum class DwarfFissionKind { None, Split, Single };
+
+DwarfFissionKind getDebugFissionKind(const Driver &D,
+                                     const llvm::opt::ArgList &Args,
+                                     llvm::opt::Arg *&Arg);
+
 } // end namespace tools
 
 } // end namespace driver

diff  --git a/clang/test/Driver/riscv-features.c b/clang/test/Driver/riscv-features.c
index 3068ae74760ba..37b6f8647d49b 100644
--- a/clang/test/Driver/riscv-features.c
+++ b/clang/test/Driver/riscv-features.c
@@ -35,3 +35,10 @@
 // RUN: not %clang -cc1 -triple riscv64-unknown-elf -target-feature +e 2>&1 | FileCheck %s -check-prefix=RV64-WITH-E
 
 // RV64-WITH-E: error: invalid feature combination: standard user-level extension 'e' requires 'rv32'
+
+// RUN: not %clang -c --target=riscv64-linux-gnu -gsplit-dwarf %s 2>&1 | FileCheck %s --check-prefix=ERR-SPLIT-DWARF
+// RUN: not %clang -c --target=riscv64 -gsplit-dwarf=single %s 2>&1 | FileCheck %s --check-prefix=ERR-SPLIT-DWARF
+// RUN: %clang -### -c --target=riscv64 -mno-relax -g -gsplit-dwarf %s 2>&1 | FileCheck %s --check-prefix=SPLIT-DWARF
+
+// ERR-SPLIT-DWARF: error: -gsplit-dwarf{{.*}} is unsupported with RISC-V linker relaxation (-mrelax)
+// SPLIT-DWARF:     "-split-dwarf-file"