[llvm] [KeyInstr][DwarfDebug] Add is_stmt emission support (PR #133495)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -0,0 +1,78 @@
+# RUN: llc %s --start-after=livedebugvalues --dwarf-use-key-instructions --filetype=obj -o - \
+# RUN: | llvm-objdump -d - --no-show-raw-insn \
+# RUN: | FileCheck %s --check-prefix=OBJ
+
+# RUN: llc %s --start-after=livedebugvalues --dwarf-use-key-instructions --filetype=obj -o - \
+# RUN: | llvm-dwarfdump - --debug-line \
+# RUN: | FileCheck %s --check-prefix=DBG
+
+# OBJ: 0000000000000000 <_Z1fPiii>:
+# OBJ-NEXT:  0:       movl    $0x0, %ebx
+# OBJ-NEXT:  5:       movl    $0x1, %ebx
+# OBJ-NEXT:  a:       movl    $0x2, %ebx
+# OBJ-NEXT:  f:       movl    $0x3, %ebx
+# OBJ-NEXT: 14:       movl    $0x4, %eax
+# OBJ-NEXT: 19:       movl    $0x5, %eax
+# OBJ-NEXT: 1e:       movl    $0x6, %eax
+# OBJ-NEXT: 23:       movl    $0x7, %eax
+# OBJ-NEXT: 28:       retq
+
+# DBG:      Address            Line   Column File   ISA Discriminator OpIndex Flags
+# DBG-NEXT: ------------------ ------ ------ ------ --- ------------- ------- -------------
+# DBG-NEXT: 0x0000000000000000      1      0      0   0             0       0  is_stmt prologue_end
+# DBG-NEXT: 0x0000000000000005      2      0      0   0             0       0  is_stmt
+# DBG-NEXT: 0x000000000000000a      2      0      0   0             0       0
+# DBG-NEXT: 0x000000000000000f      2      0      0   0             0       0
+# DBG-NEXT: 0x0000000000000014      2      0      0   0             0       0
+# DBG-NEXT: 0x0000000000000019      2      0      0   0             0       0
+# DBG-NEXT: 0x000000000000001e      2      0      0   0             0       0  is_stmt
+# DBG-NEXT: 0x0000000000000023      2      0      0   0             0       0  is_stmt
+# DBG-NEXT: 0x0000000000000029      2      0      0   0             0       0  is_stmt end_sequence
+
+## Check that interleaving atoms on the same line still produces reasonable
+## is_stmt placement (the is_stmts want to "float up" to the first instruction
+## in a contiguous set with the same line, but we don't let them float past
+## other atom groups).
+
+--- |
+  target triple = "x86_64-unknown-linux-gnu"
+
+  define hidden noundef i32 @_Z1fPiii(ptr %a, i32 %b, i32 %c, i1 %cond) local_unnamed_addr !dbg !5 {
+  entry:
+    ret i32 2
+  }
+
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!2, !3}
+  !llvm.ident = !{!4}
+
+  !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_17, file: !1, producer: "clang version 19.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, splitDebugInlining: false, nameTableKind: None)
+  !1 = !DIFile(filename: "test.cpp", directory: "/")
+  !2 = !{i32 7, !"Dwarf Version", i32 5}
+  !3 = !{i32 2, !"Debug Info Version", i32 3}
+  !4 = !{!"clang version 19.0.0"}
+  !5 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !6, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+  !6 = !DISubroutineType(types: !7)
+  !7 = !{}
+  !8 = !DILocalVariable(name: "x", scope: !5, file: !1, line: 1, type: !7)
+
+...
+---
+name:            _Z1fPiii
+alignment:       16
+body:             |
+  bb.0.entry:
+    $ebx = MOV32ri 0, debug-location !DILocation(line: 1, scope: !5) 
+    ;; is_stmt floats up here from mov 3.
+    $ebx = MOV32ri 1, debug-location !DILocation(line: 2, scope: !5, atomGroup: 1, atomRank: 1)
+    $ebx = MOV32ri 2, debug-location !DILocation(line: 2, scope: !5, atomGroup: 1, atomRank: 2)
+    $ebx = MOV32ri 3, debug-location !DILocation(line: 2, scope: !5, atomGroup: 1, atomRank: 1)
+    $eax = MOV32ri 4, debug-location !DILocation(line: 2, scope: !5)
+    $eax = MOV32ri 5, debug-location !DILocation(line: 2, scope: !5, atomGroup: 2, atomRank: 1)
----------------
OCHyams wrote:

Fixed this by addressing previous comment, good spot.

https://github.com/llvm/llvm-project/pull/133495