[Reassociate] Do not drop debug location if replacement is missing

Summary:
When reassociating an expression, do not drop the instruction's
original debug location in case the replacement location is
missing.

The debug location must at least not be dropped for inlinable
callsites of debug-info-bearing functions in debug-info-bearing
functions. Failing to do so would result in an "inlinable function "
"call in a function with debug info must have a !dbg location"
error in the verifier.

As preserving the original debug location is not expected
to result in overly jumpy debug line information, it is
preserved for all other cases too.

This fixes PR34231:
https://bugs.llvm.org/show_bug.cgi?id=34231

Original patch by David Stenberg

Reviewers: davide, craig.topper, mcrosier, dblaikie, aprantl

Reviewed By: davide, aprantl

Subscribers: aprantl

Differential Revision: https://reviews.llvm.org/D36865

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311642 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index e0ef8cfe46bf30f9a3848ea0e7ed115b7bcbbb74..58832447e1e16281e041764dc55a05794951de84 100644 (file)
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -2137,7 +2137,8 @@ void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
     DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
     I->replaceAllUsesWith(V);
     if (Instruction *VI = dyn_cast<Instruction>(V))
-      VI->setDebugLoc(I->getDebugLoc());
+      if (I->getDebugLoc())
+        VI->setDebugLoc(I->getDebugLoc());
     RedoInsts.insert(I);
     ++NumAnnihil;
     return;

diff --git a/test/Transforms/Reassociate/keep-debug-loc.ll b/test/Transforms/Reassociate/keep-debug-loc.ll
new file mode 100644 (file)
index 0000000..1a1031f
--- /dev/null
+++ b/test/Transforms/Reassociate/keep-debug-loc.ll
@@ -0,0 +1,48 @@
+; RUN: opt -S -reassociate < %s | FileCheck %s
+
+; PR34231
+;
+; Verify that the original debug location is kept if the
+; replacement debug location is missing when
+; reassociating expressions.
+
+define i16 @fn1() !dbg !3 {
+  ret i16 undef
+}
+
+define void @fn2() !dbg !6 {
+; CHECK-LABEL: @fn2
+; CHECK: call i16 @fn1(), !dbg ![[LOC1:[0-9]+]]
+; CHECK-NOT: or i16
+  %inlinable_call = call i16 @fn1(), !dbg !7
+  %dbgless_instruction = or i16 %inlinable_call, 0
+  store i16 %dbgless_instruction, i16* undef, align 1
+  unreachable
+}
+
+define void @fn3() !dbg !8 {
+; CHECK-LABEL: @fn3
+; CHECK: load i16, i16* undef, !dbg ![[LOC2:[0-9]+]]
+; CHECK-NOT: or i16
+  %instruction = load i16, i16* undef, !dbg !9
+  %dbgless_instruction = or i16 %instruction, 0
+  store i16 %dbgless_instruction, i16* undef, align 1
+  unreachable
+}
+
+; CHECK: ![[LOC1]] = !DILocation(line: 7
+; CHECK: ![[LOC2]] = !DILocation(line: 9
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly)
+!1 = !DIFile(filename: "foo.c", directory: "/")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "fn1", scope: !1, file: !1, line: 2, type: !4, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: true, unit: !0)
+!4 = !DISubroutineType(types: !5)
+!5 = !{}
+!6 = distinct !DISubprogram(name: "fn2", scope: !1, file: !1, line: 3, type: !4, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !0)
+!7 = !DILocation(line: 7, column: 10, scope: !6)
+!8 = distinct !DISubprogram(name: "fn3", scope: !1, file: !1, line: 8, type: !4, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !0)
+!9 = !DILocation(line: 9, column: 10, scope: !8)