Use of llvm::StringLiteral for string literals is a cause of relocations

[bjacob]

We discussed this theoretically in #19440 (comment), but now here's experimental proof:

ninja iree-opt && readelf -WCr ./lib/libIREECompiler.so 2>/dev/null | grep ' contains '

At current main branch (ed9a028d3), x86-64, RelWithDebInfo build:

Relocation section '.rela.dyn' at offset 0x1274108 contains 484355 entries:
Relocation section '.rela.plt' at offset 0x1d8a150 contains 47171 entries:

With the below diff applied:

Relocation section '.rela.dyn' at offset 0x1274108 contains 484354 entries:
Relocation section '.rela.plt' at offset 0x1d8a138 contains 47171 entries:

diff --git a/compiler/src/iree/compiler/Codegen/Common/MaterializeUserConfigs.cpp b/compiler/src/iree/compiler/Codegen/Common/MaterializeUserConfigs.cpp
index 92e719b76d..3bfe455390 100644
--- a/compiler/src/iree/compiler/Codegen/Common/MaterializeUserConfigs.cpp
+++ b/compiler/src/iree/compiler/Codegen/Common/MaterializeUserConfigs.cpp
@@ -172,7 +172,7 @@ struct MaterializeUserConfigsPass final
       if (succeeded(getModuleTuningSpec(moduleOp, tuningSpec))) {
         assert(tuningSpec);
         userTransformLibrary = TransformLibraryWithEntrypoint{
-            tuningSpec.get(), kKernelConfigSpecName.str()};
+            tuningSpec.get(), kKernelConfigSpecName};
       }
     }
 
diff --git a/compiler/src/iree/compiler/Codegen/Dialect/Codegen/IR/IREECodegenAttrs.h b/compiler/src/iree/compiler/Codegen/Dialect/Codegen/IR/IREECodegenAttrs.h
index 59bf10a71a..e73945278c 100644
--- a/compiler/src/iree/compiler/Codegen/Dialect/Codegen/IR/IREECodegenAttrs.h
+++ b/compiler/src/iree/compiler/Codegen/Dialect/Codegen/IR/IREECodegenAttrs.h
@@ -49,7 +49,7 @@ constexpr StringLiteral kTuningSpecEntrypointAttrName =
     "iree_codegen.tuning_spec_entrypoint";
 constexpr StringLiteral kSerializedTuningSpecAttrName =
     "iree_codegen.tuning_spec_mlirbc";
-constexpr StringLiteral kKernelConfigSpecName = "__kernel_config";
+constexpr char kKernelConfigSpecName[] = "__kernel_config";

[benvanik]

oof, that sucks - longer to link, longer to load!