[clang] [KeyInstr][Clang] Bitfield atom (PR #134648)

[Orlando Cazalet-Hyams via cfe-commits]

https://github.com/OCHyams updated https://github.com/llvm/llvm-project/pull/134648

>From 76d8a4306760fba28fc22c936b46d98263c37971 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Thu, 3 Apr 2025 19:57:39 +0100
Subject: [PATCH 1/3] [KeyInstr][Clang] Bitfield atom

This patch is part of a stack that teaches Clang to generate Key Instructions
metadata for C and C++.

The Key Instructions project is introduced, including a "quick summary" section
at the top which adds context for this PR, here:
https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668

The feature is only functional in LLVM if LLVM is built with CMake flag
LLVM_EXPERIMENTAL_KEY_INSTRUCTIONs. Eventually that flag will be removed.

The Clang-side work is demoed here:
https://github.com/llvm/llvm-project/pull/130943
---
 clang/lib/CodeGen/CGExpr.cpp                      |  3 ++-
 clang/test/DebugInfo/KeyInstructions/bitfield.cpp | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/DebugInfo/KeyInstructions/bitfield.cpp

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 2c0edd69d96e9..e72288ccd3c26 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -2672,7 +2672,8 @@ void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
   }
 
   // Write the new value back out.
-  Builder.CreateStore(SrcVal, Ptr, Dst.isVolatileQualified());
+  auto *I = Builder.CreateStore(SrcVal, Ptr, Dst.isVolatileQualified());
+  addInstToCurrentSourceAtom(I, SrcVal);
 
   // Return the new value of the bit-field, if requested.
   if (Result) {
diff --git a/clang/test/DebugInfo/KeyInstructions/bitfield.cpp b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
new file mode 100644
index 0000000000000..0586050ba8397
--- /dev/null
+++ b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang -gkey-instructions %s -gmlt -gcolumn-info -S -emit-llvm -o - \
+// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
+
+struct S { int a:3; };
+
+void foo(int x, S s) {
+// CHECK: %bf.set = or i8 %bf.clear, %bf.value, !dbg [[G1R2:!.*]]
+// CHECK: store i8 %bf.set, ptr %s, align 4, !dbg [[G1R1:!.*]]
+  s.a = x;
+}
+
+// CHECK: [[G1R2]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 2)
+// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)

>From d64c34ffe83820895a8a2487dc9e72abbc16b85c Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Wed, 21 May 2025 15:55:29 +0100
Subject: [PATCH 2/3] cc1

---
 clang/test/DebugInfo/KeyInstructions/bitfield.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/DebugInfo/KeyInstructions/bitfield.cpp b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
index 0586050ba8397..b76e6ec3d9c99 100644
--- a/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
+++ b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang -gkey-instructions %s -gmlt -gcolumn-info -S -emit-llvm -o - \
+// RUN: %clang_cc1 -gkey-instructions %s -debug-info-kind=line-tables-only -emit-llvm -o - \
 // RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
 
 struct S { int a:3; };

>From 9cfcd16fe1db7b6663b8abbcd9d797d3bbbad713 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Tue, 27 May 2025 13:30:44 +0100
Subject: [PATCH 3/3] triple and test comment

---
 clang/test/DebugInfo/KeyInstructions/bitfield.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/test/DebugInfo/KeyInstructions/bitfield.cpp b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
index b76e6ec3d9c99..a14b4fbaf5854 100644
--- a/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
+++ b/clang/test/DebugInfo/KeyInstructions/bitfield.cpp
@@ -1,6 +1,9 @@
-// RUN: %clang_cc1 -gkey-instructions %s -debug-info-kind=line-tables-only -emit-llvm -o - \
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -gkey-instructions %s -debug-info-kind=line-tables-only -emit-llvm -o - \
 // RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
 
+// Check assignments to bitfield members are given source atom groups, as this
+// has distinct codegen codepath to other variable/member assignments.
+
 struct S { int a:3; };
 
 void foo(int x, S s) {