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

[Garvit Gupta via cfe-commits]

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

>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 1/2] [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

>From 559f1d6e4221dc94cd035c0f568dea630dcb6f37 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 2/2] [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/test/Driver/riscv-features.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/clang/test/Driver/riscv-features.c b/clang/test/Driver/riscv-features.c
index d3700f71aa7e1d..15832e79d2a491 100644
--- a/clang/test/Driver/riscv-features.c
+++ b/clang/test/Driver/riscv-features.c
@@ -35,6 +35,14 @@
 // FAST-UNALIGNED-ACCESS: "-target-feature" "+fast-unaligned-access"
 // NO-FAST-UNALIGNED-ACCESS: "-target-feature" "-fast-unaligned-access"
 
+// 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"
+
 // RUN: %clang --target=riscv32-linux -### %s -fsyntax-only 2>&1 \
 // RUN:   | FileCheck %s -check-prefix=DEFAULT-LINUX
 // RUN: %clang --target=riscv64-linux -### %s -fsyntax-only 2>&1 \