[clang] dd8eb1e - [KeyInstr][Clang] Switch stmt atom (#134643)

[via cfe-commits]

Author: Orlando Cazalet-Hyams
Date: 2025-05-27T11:26:40+01:00
New Revision: dd8eb1e6737a612be204c59949ff3611c300e25a

URL: https://github.com/llvm/llvm-project/commit/dd8eb1e6737a612be204c59949ff3611c300e25a
DIFF: https://github.com/llvm/llvm-project/commit/dd8eb1e6737a612be204c59949ff3611c300e25a.diff

LOG: [KeyInstr][Clang] Switch stmt atom (#134643)

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

RFC:
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.

Added: 
    clang/test/DebugInfo/KeyInstructions/switch.c

Modified: 
    clang/lib/CodeGen/CGStmt.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 3b701116e5e4b..31d64a5a788ee 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -2293,6 +2293,8 @@ void CodeGenFunction::EmitSwitchStmt(const SwitchStmt &S) {
   // failure.
   llvm::BasicBlock *DefaultBlock = createBasicBlock("sw.default");
   SwitchInsn = Builder.CreateSwitch(CondV, DefaultBlock);
+  addInstToNewSourceAtom(SwitchInsn, CondV);
+
   if (HLSLControlFlowAttr != HLSLControlFlowHintAttr::SpellingNotCalculated) {
     llvm::MDBuilder MDHelper(CGM.getLLVMContext());
     llvm::ConstantInt *BranchHintConstant =

diff  --git a/clang/test/DebugInfo/KeyInstructions/switch.c b/clang/test/DebugInfo/KeyInstructions/switch.c
new file mode 100644
index 0000000000000..5142f204ff587
--- /dev/null
+++ b/clang/test/DebugInfo/KeyInstructions/switch.c
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -gkey-instructions -x c++ -std=c++17 %s -debug-info-kind=line-tables-only -emit-llvm -o - \
+// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank --check-prefixes=CHECK,CHECK-CXX
+
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -gkey-instructions -x c %s -debug-info-kind=line-tables-only -emit-llvm -o - \
+// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
+
+int g;
+void a(int A, int B) {
+// CHECK: entry:
+// The load gets associated with the branch rather than the store.
+// TODO: Associating it with the store may be a better choice.
+// CHECK: %0 = load i32, ptr %A.addr{{.*}}, !dbg [[G2R2:!.*]]
+// CHECK: store i32 %0, ptr @g{{.*}}, !dbg [[G1R1:!.*]]
+// CHECK: switch i32 %0, label %{{.*}} [
+// CHECK:   i32 0, label %sw.bb
+// CHECK:   i32 1, label %sw.bb1
+// CHECK: ], !dbg [[G2R1:!.*]]
+    switch ((g = A)) {
+    case 0: break;
+    case 1: {
+// CHECK: sw.bb1:
+// CHECK: %1 = load i32, ptr %B.addr{{.*}}, !dbg [[G3R2:!.*]]
+// CHECK: switch i32 %1, label %{{.*}} [
+// CHECK:   i32 0, label %sw.bb2
+// CHECK: ], !dbg [[G3R1:!.*]]
+    switch ((B)) {
+        case 0: {
+// Test that assignments in constant-folded switches don't go missing.
+// CHECK-CXX: sw.bb2:
+// CHECK-CXX: store i32 1, ptr %C{{.*}}, !dbg [[G4R1:!.*]]
+#ifdef __cplusplus
+            switch (const int C = 1; C) {
+                case 0: break;
+                case 1: break;
+                default: break;
+            }
+#endif
+        } break;
+        default: break;
+    }
+    } break;
+    default: break;
+    }
+}
+
+// CHECK: [[G2R2]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
+// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
+// CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
+// CHECK: [[G3R2]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
+// CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
+// CHECK-CXX: [[G4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)