[DebugInfo] Introduce DW_OP_LLVM_convert
Introduce a DW_OP_LLVM_convert Dwarf expression pseudo op that allows
for a convenient way to perform type conversions on the Dwarf expression
stack. As an additional bonus it paves the way for using other Dwarf
v5 ops that need to reference a base_type.
The new DW_OP_LLVM_convert is used from lib/Transforms/Utils/Local.cpp
to perform sext/zext on debug values but mainly the patch is about
preparing terrain for adding other Dwarf v5 ops that need to reference a
base_type.
For Dwarf v5 the op maps to DW_OP_convert and for earlier versions a
complex shift & mask pattern is generated to emulate sext/zext.
This is a recommit of r356442 with trivial fixes for the failing tests.
Differential Revision: https://reviews.llvm.org/D56587
llvm-svn: 356451
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index d14384f..9271e1d 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1861,21 +1861,10 @@
return None;
bool Signed = *Signedness == DIBasicType::Signedness::Signed;
-
- if (!Signed) {
- // In the unsigned case, assume that a debugger will initialize the
- // high bits to 0 and do a no-op conversion.
- return Identity(DII);
- } else {
- // In the signed case, the high bits are given by sign extension, i.e:
- // (To >> (ToBits - 1)) * ((2 ^ FromBits) - 1)
- // Calculate the high bits and OR them together with the low bits.
- SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_dup, dwarf::DW_OP_constu,
- (ToBits - 1), dwarf::DW_OP_shr,
- dwarf::DW_OP_lit0, dwarf::DW_OP_not,
- dwarf::DW_OP_mul, dwarf::DW_OP_or});
- return DIExpression::appendToStack(DII.getExpression(), Ops);
- }
+ dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
+ SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK,
+ dwarf::DW_OP_LLVM_convert, FromBits, TK});
+ return DIExpression::appendToStack(DII.getExpression(), Ops);
};
return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
}