[PATCH] D61184: [Salvage] Change salvage debug info implementation to use new DW_OP_LLVM_convert where needed

[Stephen Tozer via Phabricator via llvm-commits]

StephenTozer updated this revision to Diff 196837.
StephenTozer added a comment.

As per the previous comment, ZExt is equivalent to a Noop on the DWARF expression stack, so can be caught by the same early exit.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61184/new/

https://reviews.llvm.org/D61184

Files:
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/test/DebugInfo/salvage-cast-debug-info.ll
  llvm/test/Transforms/InstCombine/cast-mul-select.ll


Index: llvm/test/Transforms/InstCombine/cast-mul-select.ll
===================================================================
--- llvm/test/Transforms/InstCombine/cast-mul-select.ll
+++ llvm/test/Transforms/InstCombine/cast-mul-select.ll
@@ -13,6 +13,8 @@
 ; we preserve the debug information in the resulting
 ; instruction.
 ; DBGINFO-LABEL: @mul(
+; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 %x
+; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 %y
 ; DBGINFO-NEXT:    [[C:%.*]] = mul i32 {{.*}}
 ; DBGINFO-NEXT:    [[D:%.*]] = and i32 {{.*}}
 ; DBGINFO-NEXT:    call void @llvm.dbg.value(metadata i32 [[C]]
Index: llvm/test/DebugInfo/salvage-cast-debug-info.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/salvage-cast-debug-info.ll
@@ -0,0 +1,25 @@
+; RUN: opt %s -debugify -early-cse -S | FileCheck %s
+define i32 @foo(i64 %nose, i32 %more) {
+; CHECK-LABEL: @foo(
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose, metadata [[V1:![0-9]+]], metadata !DIExpression(DW_OP_LLVM_convert, 32
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose.shift, metadata [[V2:![0-9]+]]
+; CHECK: call void @llvm.dbg.value(metadata i64 %nose.shift, metadata [[V3:![0-9]+]], metadata !DIExpression(DW_OP_LLVM_convert, 32
+
+entry:
+  %nose.trunc = trunc i64 %nose to i32
+  %nose.shift = lshr i64 %nose, 32
+  %nose.trunc.2 = trunc i64 %nose.shift to i32
+  %add = add nsw i32 %more, 1
+  ret i32 %add
+}
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 2}
+!1 = !{i32 7, !"PIC Level", i32 2}
+!2 = !{!"clang version 9.0.0 "}
+
+; CHECK: [[V1]] = !DILocalVariable(
+; CHECK: [[V2]] = !DILocalVariable(
+; CHECK: [[V3]] = !DILocalVariable(
Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -1669,6 +1669,22 @@
     // No-op casts and zexts are irrelevant for debug info.
     if (CI->isNoopCast(DL) || isa<ZExtInst>(&I))
       return SrcDIExpr;
+    Type *Type = CI->getType();
+    // There does not appear to be any op for vector casting.
+    if (Type->isVectorTy())
+      return nullptr;
+
+    if (isa<TruncInst>(&I) || isa<SExtInst>(&I)) {
+      unsigned TypeBitSize = Type->getScalarSizeInBits();
+
+      // The result of the cast will be sign extended iff the instruction is a
+      // SExt; signedness is otherwise irrelevant on the expression stack.
+      unsigned Encoding =
+          isa<SExtInst>(&I) ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
+
+      return applyOps({dwarf::DW_OP_LLVM_convert, TypeBitSize, Encoding});
+    }
+
     return nullptr;
   } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
     unsigned BitWidth =


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