[clang] [RISCV] Disable generation of asynchronous unwind tables for RISCV ba… (PR #81727)

[Garvit Gupta via cfe-commits]

https://github.com/quic-garvgupt created https://github.com/llvm/llvm-project/pull/81727

The below culprit patch enabled the generation of asynchronous unwind tables (-funwind-tables=2) by default for RISCV for both linux and RISCVToolChain baremetal object. However, since there are 2 baremetal toolchain objects for RISCV, this created a discrepancy between their behavior. Moreover, enabling the generation of asynchronous unwind tables based on whether `-gcc-toolchain` option is present or not doesn't seem to be the best criteria to decide on the same. This patch make the behavior consistent by disabling the unwind tables in RISCVToolChain Baremetal object.

Culprit Patch - https://reviews.llvm.org/D145164


>From 42211bccd8ffc60751234ab5695be135ea8b6373 Mon Sep 17 00:00:00 2001
From: Garvit Gupta <quic_garvgupt at quicinc.com>
Date: Wed, 14 Feb 2024 03:00:20 -0800
Subject: [PATCH] [RISCV] Disable generation of asynchronous unwind tables for
 RISCV baremetal

The below culprit patch enabled the generation of asynchronous unwind tables
(-funwind-tables=2) by default for RISCV for both linux and RISCVToolChain
baremetal object. However, since there are 2 baremetal toolchain objects for
RISCV, this created a discrepancy between their behavior. Moreover, enabling
the generation of asynchronous unwind tables based on whether `-gcc-toolchain`
option is present or not doesn't seem to be the best criteria to decide on
the same.

Culprit Patch - https://reviews.llvm.org/D145164
---
 clang/lib/Driver/ToolChains/RISCVToolchain.cpp | 5 +++++
 clang/lib/Driver/ToolChains/RISCVToolchain.h   | 2 ++
 clang/test/Driver/clang-translation.c          | 8 ++++++++
 3 files changed, 15 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/RISCVToolchain.cpp b/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
index 85beb945cbf6fc..624099d21ae124 100644
--- a/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
+++ b/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
@@ -86,6 +86,11 @@ RISCVToolChain::GetUnwindLibType(const llvm::opt::ArgList &Args) const {
   return ToolChain::UNW_None;
 }
 
+ToolChain::UnwindTableLevel RISCVToolChain::getDefaultUnwindTableLevel(
+    const llvm::opt::ArgList &Args) const {
+  return UnwindTableLevel::None;
+}
+
 void RISCVToolChain::addClangTargetOptions(
     const llvm::opt::ArgList &DriverArgs,
     llvm::opt::ArgStringList &CC1Args,
diff --git a/clang/lib/Driver/ToolChains/RISCVToolchain.h b/clang/lib/Driver/ToolChains/RISCVToolchain.h
index cec817ef7190be..fa0aa265d842bb 100644
--- a/clang/lib/Driver/ToolChains/RISCVToolchain.h
+++ b/clang/lib/Driver/ToolChains/RISCVToolchain.h
@@ -28,6 +28,8 @@ class LLVM_LIBRARY_VISIBILITY RISCVToolChain : public Generic_ELF {
   RuntimeLibType GetDefaultRuntimeLibType() const override;
   UnwindLibType
   GetUnwindLibType(const llvm::opt::ArgList &Args) const override;
+  UnwindTableLevel
+  getDefaultUnwindTableLevel(const llvm::opt::ArgList &Args) const override;
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                             llvm::opt::ArgStringList &CC1Args) const override;
diff --git a/clang/test/Driver/clang-translation.c b/clang/test/Driver/clang-translation.c
index a7343ea18b2135..64d55f1b88ea6d 100644
--- a/clang/test/Driver/clang-translation.c
+++ b/clang/test/Driver/clang-translation.c
@@ -421,3 +421,11 @@
 // MIPSN32R6EL: "-target-cpu" "mips64r6"
 // MIPSN32R6EL: "-target-abi" "n32"
 // MIPSN32R6EL: "-mfloat-abi" "hard"
+
+// RUN: %clang --target=riscv32-unknown-elf --gcc-toolchain="" -### %s 2>&1 | FileCheck %s -check-prefix=NOUWTABLE
+// RUN: %clang --target=riscv32-unknown-elf --gcc-toolchain="" -fasynchronous-unwind-tables -### %s 2>&1 | FileCheck %s -check-prefix=UWTABLE
+// RUN: %clang --target=riscv64-unknown-elf --gcc-toolchain="" -### %s 2>&1 | FileCheck %s -check-prefix=NOUWTABLE
+// RUN: %clang --target=riscv64-unknown-elf --gcc-toolchain="" -fasynchronous-unwind-tables -### %s 2>&1 | FileCheck %s -check-prefix=UWTABLE
+//
+// UWTABLE: "-funwind-tables=2"
+// NOUWTABLE-NOT: "-funwind-tables=2"
\ No newline at end of file