[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[Aditya Kumar via Phabricator via cfe-commits]

hiraditya added a comment.

cc: @t.p.northover does this fix look reasonable for PR37240?


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[David Tellenbach via Phabricator via cfe-commits]

tellenbach added a comment.

In D68076#2131108 , @hiraditya wrote:

> do we have a plan to follow up on this patch?


Hi! I'm currently not working on this (and LLVM in general) anymore. However, 
the issue seems to be still present and this patch would fix it. I have in mind 
that I've checked GCC recently and they seem to do something similar. I can 
check again but will probably take some time.

Thanks for bringing this up again!


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[Aditya Kumar via Phabricator via cfe-commits]

hiraditya added a comment.
Herald added a subscriber: danielkiss.

do we have a plan to follow up on this patch?


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[David Tellenbach via Phabricator via cfe-commits]

tellenbach added a comment.

This patch would fix  PR37240 but is probably not the most optimal solution. 
For other ideas see 
http://lists.llvm.org/pipermail/llvm-dev/2019-September/135433.html 
. I'll 
leave this patch open until other possibilities have been accepted or abandoned 
and will abandon or fix this patch then.


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[Aditya Kumar via Phabricator via cfe-commits]

hiraditya added a comment.

Can we add a test to verify cfi instructions are present without debug flag.


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[David Tellenbach via Phabricator via cfe-commits]

tellenbach added a comment.

This would fix PR37240 


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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[David Tellenbach via Phabricator via cfe-commits]

tellenbach added a comment.

Please also see the ongoing discussion on the mailing list: 
http://lists.llvm.org/pipermail/llvm-dev/2019-September/135433.html 



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[PATCH] D68076: [AArch64] Enable unwind tables by default for Gnu targets

[David Tellenbach via Phabricator via cfe-commits]

tellenbach created this revision.
Herald added subscribers: cfe-commits, kristof.beyls, aprantl.
Herald added a project: clang.

Currently the following situation can occur: During AArch64 frame lowering cfi 
instructions get emitted if debug information is generated but not if not. 
Since cfi instructions act as scheduling boundaries during instruction 
scheduling this leads to different scheduling regions and therefore different 
assembly depending on whether debug information is generated or not.

This patch fixes this problem by enabling unwind tables by default on AArch64 
when compiling for a Gnu targets.


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Files:
  clang/lib/Driver/ToolChains/Gnu.cpp
  clang/test/Driver/clang-translation.c


Index: clang/test/Driver/clang-translation.c
===
--- clang/test/Driver/clang-translation.c
+++ clang/test/Driver/clang-translation.c
@@ -150,6 +150,10 @@
 // ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el2"
 // ARMv8_THREAD_POINTER_EL3: "-target-feature" "+tpidr-el3"
 
+// RUN: %clang -target aarch64-linux -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=AARCH64_LINUX_DEFAULT_UNWIND_TABLES %s
+// AARCH64_LINUX_DEFAULT_UNWIND_TABLES: "-munwind-tables"
+
 // RUN: %clang -target powerpc64-unknown-linux-gnu \
 // RUN: -### -S %s -mcpu=G5 2>&1 | FileCheck -check-prefix=PPCG5 %s
 // PPCG5: clang
Index: clang/lib/Driver/ToolChains/Gnu.cpp
===
--- clang/lib/Driver/ToolChains/Gnu.cpp
+++ clang/lib/Driver/ToolChains/Gnu.cpp
@@ -2540,7 +2540,8 @@
 }
 
 bool Generic_GCC::IsUnwindTablesDefault(const ArgList &Args) const {
-  return getArch() == llvm::Triple::x86_64;
+  return getArch() == llvm::Triple::x86_64 ||
+ getArch() == llvm::Triple::aarch64;
 }
 
 bool Generic_GCC::isPICDefault() const {


Index: clang/test/Driver/clang-translation.c
===
--- clang/test/Driver/clang-translation.c
+++ clang/test/Driver/clang-translation.c
@@ -150,6 +150,10 @@
 // ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el2"
 // ARMv8_THREAD_POINTER_EL3: "-target-feature" "+tpidr-el3"
 
+// RUN: %clang -target aarch64-linux -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=AARCH64_LINUX_DEFAULT_UNWIND_TABLES %s
+// AARCH64_LINUX_DEFAULT_UNWIND_TABLES: "-munwind-tables"
+
 // RUN: %clang -target powerpc64-unknown-linux-gnu \
 // RUN: -### -S %s -mcpu=G5 2>&1 | FileCheck -check-prefix=PPCG5 %s
 // PPCG5: clang
Index: clang/lib/Driver/ToolChains/Gnu.cpp
===
--- clang/lib/Driver/ToolChains/Gnu.cpp
+++ clang/lib/Driver/ToolChains/Gnu.cpp
@@ -2540,7 +2540,8 @@
 }
 
 bool Generic_GCC::IsUnwindTablesDefault(const ArgList &Args) const {
-  return getArch() == llvm::Triple::x86_64;
+  return getArch() == llvm::Triple::x86_64 ||
+ getArch() == llvm::Triple::aarch64;
 }
 
 bool Generic_GCC::isPICDefault() const {
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