[lldb] [llvm] Add support for using foreign type units in .debug_names. (PR #87740)

[Alex Langford via llvm-commits]

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+// REQUIRES: lld
+
+// This test will make a type that will be compiled differently into two
+// different .dwo files in a type unit with the same type hash, but with
+// differing contents. I have discovered that the hash for the type unit is
+// simply based off of the typename and doesn't seem to differ when the contents
+// differ, so that will help us test foreign type units in the .debug_names
+// section of the main executable. When a DWP file is made, only one type unit
+// will be kept and the type unit that is kept has the .dwo file name that it
+// came from. When LLDB loads the foreign type units, it needs to verify that
+// any entries from foreign type units come from the right .dwo file. We test
+// this since the contents of type units are not always the same even though
+// they have the same type hash. We don't want invalid accelerator table entries
+// to come from one .dwo file and be used on a type unit from another since this
+// could cause invalid lookups to happen. LLDB knows how to track down which
+// .dwo file a type unit comes from by looking at the DW_AT_dwo_name attribute
+// in the DW_TAG_type_unit.
+
+// Now test with DWARF5
+// RUN: %clang -target x86_64-pc-linux -gdwarf-5 -gsplit-dwarf \
+// RUN:   -fdebug-types-section -gpubnames -c %s -o %t.main.o
+// RUN: %clang -target x86_64-pc-linux -gdwarf-5 -gsplit-dwarf -DVARIANT \
+// RUN:   -fdebug-types-section -gpubnames -c %s -o %t.foo.o
+// RUN: ld.lld %t.main.o %t.foo.o -o %t
+
+// First we check when we make the .dwp file with %t.main.dwo first so it will
+// pick the type unit from %t.main.dwo. Verify we find only the types from
+// %t.main.dwo's type unit.
+// RUN: llvm-dwp %t.main.dwo %t.foo.dwo -o %t.dwp
+// RUN: %lldb \
+// RUN:   -o "type lookup IntegerType" \
+// RUN:   -o "type lookup FloatType" \
+// RUN:   -o "type lookup IntegerType" \
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bulbazord wrote:

Why look up IntegerType twice? 

https://github.com/llvm/llvm-project/pull/87740