Re: [PATCH] Enable using llvm jitlink as an alternative llvm jit linker of old Rtdyld.

Hi,

I am new to the postgres community and apologise for resending this as the
previous one didn't include patch properly and didn't cc reviewers (maybe
the reason it has been buried in mailing list for months)

Adding to previous email, this patch exposes its own C API for creating
ObjectLinkingLayer in a similar fashion as
LLVMOrcCreateRTDyldObjectLinkingLayerWithSectionMemoryManager since orc
doesn't expose it yet.

Thanks and really appreciate if someone can offer a review to this and help
get it merged.

Cheers,
Alex

On Mon, Aug 29, 2022 at 5:46 PM Alex Fan <alex(dot)fan(dot)q(at)gmail(dot)com> wrote:

> This brings the bonus of support jitting on riscv64 (included in this
> patch)
> and other platforms Rtdyld doesn't support, e.g. windows COFF.
>
> Currently, llvm doesn't expose jitlink (ObjectLinkingLayer) via C API, so
> a wrapper is added. This also adds minor llvm 15 compat fix that is needed
> ---
> config/llvm.m4 | 1 +
> src/backend/jit/llvm/llvmjit.c | 67 +++++++++++++++++++++++++--
> src/backend/jit/llvm/llvmjit_wrap.cpp | 35 ++++++++++++++
> src/include/jit/llvmjit.h | 9 ++++
> 4 files changed, 108 insertions(+), 4 deletions(-)
>
> diff --git a/config/llvm.m4 b/config/llvm.m4
> index 3a75cd8b4d..a31b8b304a 100644
> --- a/config/llvm.m4
> +++ b/config/llvm.m4
> @@ -75,6 +75,7 @@ AC_DEFUN([PGAC_LLVM_SUPPORT],
> engine) pgac_components="$pgac_components $pgac_component";;
> debuginfodwarf) pgac_components="$pgac_components $pgac_component";;
> orcjit) pgac_components="$pgac_components $pgac_component";;
> + jitlink) pgac_components="$pgac_components $pgac_component";;
> passes) pgac_components="$pgac_components $pgac_component";;
> native) pgac_components="$pgac_components $pgac_component";;
> perfjitevents) pgac_components="$pgac_components $pgac_component";;
> diff --git a/src/backend/jit/llvm/llvmjit.c
> b/src/backend/jit/llvm/llvmjit.c
> index 6c72d43beb..d8b840da8c 100644
> --- a/src/backend/jit/llvm/llvmjit.c
> +++ b/src/backend/jit/llvm/llvmjit.c
> @@ -229,6 +229,11 @@ llvm_release_context(JitContext *context)
> LLVMModuleRef
> llvm_mutable_module(LLVMJitContext *context)
> {
> +#ifdef __riscv
> + const char* abiname;
> + const char* target_abi = "target-abi";
> + LLVMMetadataRef abi_metadata;
> +#endif
> llvm_assert_in_fatal_section();
>
> /*
> @@ -241,6 +246,40 @@ llvm_mutable_module(LLVMJitContext *context)
> context->module = LLVMModuleCreateWithName("pg");
> LLVMSetTarget(context->module, llvm_triple);
> LLVMSetDataLayout(context->module, llvm_layout);
> +#ifdef __riscv
> +#if __riscv_xlen == 64
> +#ifdef __riscv_float_abi_double
> + abiname = "lp64d";
> +#elif defined(__riscv_float_abi_single)
> + abiname = "lp64f";
> +#else
> + abiname = "lp64";
> +#endif
> +#elif __riscv_xlen == 32
> +#ifdef __riscv_float_abi_double
> + abiname = "ilp32d";
> +#elif defined(__riscv_float_abi_single)
> + abiname = "ilp32f";
> +#else
> + abiname = "ilp32";
> +#endif
> +#else
> + elog(ERROR, "unsupported riscv xlen %d", __riscv_xlen);
> +#endif
> + /*
> + * set this manually to avoid llvm defaulting to soft
> float and
> + * resulting in linker error: `can't link double-float
> modules
> + * with soft-float modules`
> + * we could set this for TargetMachine via MCOptions, but
> there
> + * is no C API for it
> + * ref:
> https://github.com/llvm/llvm-project/blob/afa520ab34803c82587ea6759bfd352579f741b4/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp#L90
> + */
> + abi_metadata = LLVMMDStringInContext2(
> + LLVMGetModuleContext(context->module),
> + abiname, strlen(abiname));
> + LLVMAddModuleFlag(context->module,
> LLVMModuleFlagBehaviorOverride,
> + target_abi, strlen(target_abi), abi_metadata);
> +#endif
> }
>
> return context->module;
> @@ -786,6 +825,8 @@ llvm_session_initialize(void)
> char *error = NULL;
> char *cpu = NULL;
> char *features = NULL;
> + LLVMRelocMode reloc=LLVMRelocDefault;
> + LLVMCodeModel codemodel=LLVMCodeModelJITDefault;
> LLVMTargetMachineRef opt0_tm;
> LLVMTargetMachineRef opt3_tm;
>
> @@ -820,16 +861,21 @@ llvm_session_initialize(void)
> elog(DEBUG2, "LLVMJIT detected CPU \"%s\", with features \"%s\"",
> cpu, features);
>
> +#ifdef __riscv
> + reloc=LLVMRelocPIC;
> + codemodel=LLVMCodeModelMedium;
> +#endif
> +
> opt0_tm =
> LLVMCreateTargetMachine(llvm_targetref, llvm_triple, cpu,
> features,
>
> LLVMCodeGenLevelNone,
> -
> LLVMRelocDefault,
> -
> LLVMCodeModelJITDefault);
> + reloc,
> + codemodel);
> opt3_tm =
> LLVMCreateTargetMachine(llvm_targetref, llvm_triple, cpu,
> features,
>
> LLVMCodeGenLevelAggressive,
> -
> LLVMRelocDefault,
> -
> LLVMCodeModelJITDefault);
> + reloc,
> + codemodel);
>
> LLVMDisposeMessage(cpu);
> cpu = NULL;
> @@ -1112,7 +1158,11 @@ llvm_resolve_symbols(LLVMOrcDefinitionGeneratorRef
> GeneratorObj, void *Ctx,
> LLVMOrcJITDylibRef JD,
> LLVMOrcJITDylibLookupFlags JDLookupFlags,
> LLVMOrcCLookupSet LookupSet,
> size_t LookupSetSize)
> {
> +#if LLVM_VERSION_MAJOR > 14
> + LLVMOrcCSymbolMapPairs symbols =
> palloc0(sizeof(LLVMOrcCSymbolMapPair) * LookupSetSize);
> +#else
> LLVMOrcCSymbolMapPairs symbols =
> palloc0(sizeof(LLVMJITCSymbolMapPair) * LookupSetSize);
> +#endif
> LLVMErrorRef error;
> LLVMOrcMaterializationUnitRef mu;
>
> @@ -1160,6 +1210,10 @@ llvm_log_jit_error(void *ctx, LLVMErrorRef error)
> static LLVMOrcObjectLayerRef
> llvm_create_object_layer(void *Ctx, LLVMOrcExecutionSessionRef ES, const
> char *Triple)
> {
> +#if defined(USE_JITLINK)
> + LLVMOrcObjectLayerRef objlayer =
> + LLVMOrcCreateJitlinkObjectLinkingLayer(ES);
> +#else
> LLVMOrcObjectLayerRef objlayer =
> LLVMOrcCreateRTDyldObjectLinkingLayerWithSectionMemoryManager(ES);
>
> @@ -1179,6 +1233,7 @@ llvm_create_object_layer(void *Ctx,
> LLVMOrcExecutionSessionRef ES, const char *T
>
>
> LLVMOrcRTDyldObjectLinkingLayerRegisterJITEventListener(objlayer, l);
> }
> +#endif
> #endif
>
> return objlayer;
> @@ -1230,7 +1285,11 @@ llvm_create_jit_instance(LLVMTargetMachineRef tm)
> * Symbol resolution support for "special" functions, e.g. a call
> into an
> * SQL callable function.
> */
> +#if LLVM_VERSION_MAJOR > 14
> + ref_gen =
> LLVMOrcCreateCustomCAPIDefinitionGenerator(llvm_resolve_symbols, NULL,
> NULL);
> +#else
> ref_gen =
> LLVMOrcCreateCustomCAPIDefinitionGenerator(llvm_resolve_symbols, NULL);
> +#endif
> LLVMOrcJITDylibAddGenerator(LLVMOrcLLJITGetMainJITDylib(lljit),
> ref_gen);
>
> return lljit;
> diff --git a/src/backend/jit/llvm/llvmjit_wrap.cpp
> b/src/backend/jit/llvm/llvmjit_wrap.cpp
> index 8f11cc02b2..29f21f1715 100644
> --- a/src/backend/jit/llvm/llvmjit_wrap.cpp
> +++ b/src/backend/jit/llvm/llvmjit_wrap.cpp
> @@ -27,6 +27,10 @@ extern "C"
> #include <llvm/Support/Host.h>
>
> #include "jit/llvmjit.h"
> +#ifdef USE_JITLINK
> +#include "llvm/ExecutionEngine/JITLink/EHFrameSupport.h"
> +#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
> +#endif
>
>
> /*
> @@ -48,6 +52,19 @@ char *LLVMGetHostCPUFeatures(void) {
> for (auto &F : HostFeatures)
> Features.AddFeature(F.first(), F.second);
>
> +#if defined(__riscv)
> + /* getHostCPUName returns "generic-rv[32|64]", which lacks all
> features */
> + Features.AddFeature("m", true);
> + Features.AddFeature("a", true);
> + Features.AddFeature("c", true);
> +# if defined(__riscv_float_abi_single)
> + Features.AddFeature("f", true);
> +# endif
> +# if defined(__riscv_float_abi_double)
> + Features.AddFeature("d", true);
> +# endif
> +#endif
> +
> return strdup(Features.getString().c_str());
> }
> #endif
> @@ -76,3 +93,21 @@ LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32
> Idx)
> */
> return LLVMGetAttributeCountAtIndex(F, Idx);
> }
> +
> +#ifdef USE_JITLINK
> +/*
> + * There is no public C API to create ObjectLinkingLayer for JITLINK,
> create our own
> + */
> +DEFINE_SIMPLE_CONVERSION_FUNCTIONS(llvm::orc::ExecutionSession,
> LLVMOrcExecutionSessionRef)
> +DEFINE_SIMPLE_CONVERSION_FUNCTIONS(llvm::orc::ObjectLayer,
> LLVMOrcObjectLayerRef)
> +
> +LLVMOrcObjectLayerRef
> +LLVMOrcCreateJitlinkObjectLinkingLayer(LLVMOrcExecutionSessionRef ES)
> +{
> + assert(ES && "ES must not be null");
> + auto ObjLinkingLayer = new
> llvm::orc::ObjectLinkingLayer(*unwrap(ES));
> +
> ObjLinkingLayer->addPlugin(std::make_unique<llvm::orc::EHFrameRegistrationPlugin>(
> + *unwrap(ES),
> std::make_unique<llvm::jitlink::InProcessEHFrameRegistrar>()));
> + return wrap(ObjLinkingLayer);
> +}
> +#endif
> diff --git a/src/include/jit/llvmjit.h b/src/include/jit/llvmjit.h
> index 4541f9a2c4..85a0cfe5e0 100644
> --- a/src/include/jit/llvmjit.h
> +++ b/src/include/jit/llvmjit.h
> @@ -19,6 +19,11 @@
>
> #include <llvm-c/Types.h>
>
> +#if defined(__riscv) && LLVM_VERSION_MAJOR >= 15
> +#include <llvm-c/Orc.h>
> +#define USE_JITLINK
> +/* else use legacy RTDyld */
> +#endif
>
> /*
> * File needs to be includable by both C and C++ code, and include other
> @@ -134,6 +139,10 @@ extern char *LLVMGetHostCPUFeatures(void);
>
> extern unsigned LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32
> Idx);
>
> +#ifdef USE_JITLINK
> +extern LLVMOrcObjectLayerRef
> LLVMOrcCreateJitlinkObjectLinkingLayer(LLVMOrcExecutionSessionRef ES);
> +#endif
> +
> #ifdef __cplusplus
> } /* extern "C" */
> #endif
> --
> 2.37.2
>
>