[KeyInstr] Complex assignment atoms

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:
#130943

Author: OCHyams

clang/lib/CodeGen/CGExprComplex.cpp

@@ -461,8 +461,12 @@ void ComplexExprEmitter::EmitStoreOfComplex(ComplexPairTy Val, LValue lvalue,
   Address RealPtr = CGF.emitAddrOfRealComponent(Ptr, lvalue.getType());
   Address ImagPtr = CGF.emitAddrOfImagComponent(Ptr, lvalue.getType());
 
-  Builder.CreateStore(Val.first, RealPtr, lvalue.isVolatileQualified());
-  Builder.CreateStore(Val.second, ImagPtr, lvalue.isVolatileQualified());
+  auto *R =
+      Builder.CreateStore(Val.first, RealPtr, lvalue.isVolatileQualified());
+  CGF.addInstToCurrentSourceAtom(R, Val.first);
+  auto *I =
+      Builder.CreateStore(Val.second, ImagPtr, lvalue.isVolatileQualified());
+  CGF.addInstToCurrentSourceAtom(I, Val.second);
 }
 
 
@@ -1209,6 +1213,7 @@ LValue ComplexExprEmitter::
 EmitCompoundAssignLValue(const CompoundAssignOperator *E,
           ComplexPairTy (ComplexExprEmitter::*Func)(const BinOpInfo&),
                          RValue &Val) {
+  ApplyAtomGroup Grp(CGF.getDebugInfo());
   TestAndClearIgnoreReal();
   TestAndClearIgnoreImag();
   QualType LHSTy = E->getLHS()->getType();
@@ -1356,6 +1361,7 @@ LValue ComplexExprEmitter::EmitBinAssignLValue(const BinaryOperator *E,
 }
 
 ComplexPairTy ComplexExprEmitter::VisitBinAssign(const BinaryOperator *E) {
+  ApplyAtomGroup Grp(CGF.getDebugInfo());
   ComplexPairTy Val;
   LValue LV = EmitBinAssignLValue(E, Val);
 

clang/test/DebugInfo/KeyInstructions/complex.c

@@ -0,0 +1,40 @@
+
+// RUN: %clang -gkey-instructions -x c++ %s -gmlt -gcolumn-info -S -emit-llvm -o - -Wno-unused-variable \
+// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
+
+// RUN: %clang -gkey-instructions -x c %s -gmlt -gcolumn-info -S -emit-llvm -o - -Wno-unused-variable \
+// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
+
+_Complex float ci;
+void test() {
+// CHECK: %ci.real = load float, ptr @ci{{.*}}, !dbg [[G1R2:!.*]]
+// CHECK: %ci.imag = load float, ptr getelementptr inbounds nuw ({ float, float }, ptr @ci, i32 0, i32 1){{.*}}, !dbg [[G1R2]]
+// CHECK: store float %ci.real, ptr %lc.realp{{.*}}, !dbg [[G1R1:!.*]]
+// CHECK: store float %ci.imag, ptr %lc.imagp{{.*}}, !dbg [[G1R1]]
+  _Complex float lc = ci;
+
+// CHECK: %ci.real1 = load float, ptr @ci{{.*}}, !dbg [[G2R2:!.*]]
+// CHECK: %ci.imag2 = load float, ptr getelementptr inbounds nuw ({ float, float }, ptr @ci, i32 0, i32 1){{.*}}, !dbg [[G2R2]]
+// CHECK: store float %ci.real1, ptr @ci{{.*}}, !dbg [[G2R1:!.*]]
+// CHECK: store float %ci.imag2, ptr getelementptr inbounds nuw ({ float, float }, ptr @ci, i32 0, i32 1){{.*}}, !dbg [[G2R1]]
+  ci = ci;
+
+// CHECK: %add.r = fadd float %ci.real5, %ci.real3, !dbg [[G3R2:!.*]]
+// CHECK: %add.i = fadd float %ci.imag6, %ci.imag4, !dbg [[G3R2]]
+// CHECK: store float %add.r, ptr @ci{{.*}}, !dbg [[G3R1:!.*]]
+// CHECK: store float %add.i, ptr getelementptr inbounds nuw ({ float, float }, ptr @ci, i32 0, i32 1){{.*}}, !dbg [[G3R1]]
+  ci += ci;
+
+// CHECK: %add = fadd float %0, %1, !dbg [[G4R2:!.*]]
+// CHECK: store float %add, ptr getelementptr inbounds nuw ({ float, float }, ptr @ci, i32 0, i32 1){{.*}}, !dbg [[G4R1:!.*]]
+  __imag ci = __imag ci + __imag ci;
+}
+
+// CHECK: [[G1R2]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 2)
+// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
+// CHECK: [[G2R2]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
+// CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
+// CHECK: [[G3R2]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
+// CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
+// CHECK: [[G4R2]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 2)
+// CHECK: [[G4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)