[llvm] 81cad0b - Make sure PHIElimination doesn't copy debug locations across basic blocks.

[Adrian Prantl via llvm-commits]

Author: Adrian Prantl
Date: 2021-04-20T17:03:29-07:00
New Revision: 81cad0be687e3db027b6035e2193a805eb1b6ced

URL: https://github.com/llvm/llvm-project/commit/81cad0be687e3db027b6035e2193a805eb1b6ced
DIFF: https://github.com/llvm/llvm-project/commit/81cad0be687e3db027b6035e2193a805eb1b6ced.diff

LOG: Make sure PHIElimination doesn't copy debug locations across basic blocks.

PHIElimination may insert copy instructions in multiple basic
blocks. Moving debug locations across basic block boundaries would be
misleading as illustrated by the test case.

rdar://75463656

Differential Revision: https://reviews.llvm.org/D100886

Added: 
    llvm/test/CodeGen/AArch64/PHIElimination-debugloc.mir

Modified: 
    llvm/lib/CodeGen/PHIElimination.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index b8e2b5701aa7a..bd586efd18136 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -475,9 +475,10 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB,
           if (DefMI->isImplicitDef())
             ImpDefs.insert(DefMI);
       } else {
-        NewSrcInstr =
-            TII->createPHISourceCopy(opBlock, InsertPos, MPhi->getDebugLoc(),
-                                     SrcReg, SrcSubReg, IncomingReg);
+        // Delete the debug location, since the copy is inserted into a
+        // 
diff erent basic block.
+        NewSrcInstr = TII->createPHISourceCopy(opBlock, InsertPos, nullptr,
+                                               SrcReg, SrcSubReg, IncomingReg);
       }
     }
 

diff  --git a/llvm/test/CodeGen/AArch64/PHIElimination-debugloc.mir b/llvm/test/CodeGen/AArch64/PHIElimination-debugloc.mir
new file mode 100644
index 0000000000000..61101491e9d9f
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/PHIElimination-debugloc.mir
@@ -0,0 +1,41 @@
+# RUN: llc -mtriple=aarch64-linux-gnu -verify-machineinstrs -o - %s \
+# RUN:   -run-pass=livevars,phi-node-elimination,twoaddressinstruction \
+# RUN:   -no-phi-elim-live-out-early-exit=1 -phi-elim-split-all-critical-edges=1 \
+# RUN: | FileCheck %s
+
+--- |
+  define void @test() !dbg !7 {
+  entry:
+    ret void, !dbg !14
+  }
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4}
+
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Adrian", emissionKind: FullDebug)
+  !1 = !DIFile(filename: "/tmp/t.c", directory: "/")
+  !2 = !{}
+  !3 = !{i32 2, !"Dwarf Version", i32 2}
+  !4 = !{i32 2, !"Debug Info Version", i32 4}
+  !5 = !{i32 1, !"PIC Level", i32 2}
+  !7 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
+  !8 = !DISubroutineType(types: !{})
+  !14 = !DILocation(line: 1, column: 0, scope: !7)
+
+---
+name: test
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $nzcv, $wzr
+    Bcc 8, %bb.2, implicit $nzcv
+
+  ; CHECK-LABEL: bb.1:
+  bb.1:
+    %x:gpr32 = COPY $wzr
+  ; Test that the debug location is not copied into bb1!
+  ; CHECK: %3:gpr32 = COPY killed %x{{$}}
+  ; CHECK-LABEL: bb.2:
+  bb.2:
+    %y:gpr32 = PHI %x:gpr32, %bb.1, undef %undef:gpr32, %bb.0, debug-location !14
+    $wzr = COPY %y:gpr32
+...