[llvm] [SelectionDAG]Salvage debuginfo when combining load and sext instrs. (PR #169779)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -0,0 +1,54 @@
+
+# RUN: llc -O2 %s -mtriple=x86_64-unkown-linux -start-before=x86-isel -stop-after=x86-isel -o - | FileCheck %s --check-prefix=MIR
+# RUN: llc -O2 %s -start-before=x86-isel -mtriple=x86_64-unkown-linux --filetype=obj -o %t.o 
+# RUN: llvm-dwarfdump %t.o --name Idx | FileCheck %s --check-prefix=DUMP
+
+# MIR: ![[IDX:[0-9]+]] = !DILocalVariable(name: "Idx"
+# MIR-LABEL: bb.0
+# MIR: %{{[0-9a-zA-Z]+}}{{.*}} = MOVSX64rm32 ${{.*}}, 1, $noreg, @GlobArr, $noreg, debug-instr-number [[INSTR_NUM:[0-9]+]]
+# MIR-NEXT: DBG_INSTR_REF ![[IDX]], !DIExpression(DW_OP_LLVM_arg, 0), dbg-instr-ref([[INSTR_NUM]], 0)
+# MIR-NEXT DBG_INSTR_REF ![[IDX]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_fragment, 0, 32), dbg-instr-ref([[INSTR_NUM]], 0)
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OCHyams wrote:

Missing `:` after MIR-NEXT

But more broadly, why do we emit two DBG_INSTR_REFs?

https://github.com/llvm/llvm-project/pull/169779