[llvm] Improve how lowering of formal arguments interprets a value of 'kernel_arg_type' (PR #78730)
Vyacheslav Levytskyy via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 19 07:38:10 PST 2024
https://github.com/VyacheslavLevytskyy created https://github.com/llvm/llvm-project/pull/78730
The goal of this PR is to tolerate differences between description of formal arguments by function metadata (represented by "kernel_arg_type") and LLVM actual parameter types. A compiler may use "kernel_arg_type" of function metadata fields to encode detailed type information, whereas LLVM IR may utilize for an actual parameter a more general type, in particular, opaque pointer type. This PR proposes to resolve this by a fallback to LLVM actual parameter types during the lowering of formal function arguments in cases when the type can't be created by string content of "kernel_arg_type", i.e., when "kernel_arg_type" contains a type unknown for the SPIR-V Backend.
An example of the issue manifestation is https://github.com/KhronosGroup/SPIRV-LLVM-Translator/blob/main/test/transcoding/KernelArgTypeInOpString.ll, where a compiler generates for the following kernel function detailed `kernel_arg_type` info in a form of `!{!"image_kernel_data*", !"myInt", !"struct struct_name*"}`, and in LLVM IR same arguments are referred to as `@foo(ptr addrspace(1) %in, i32 %out, ptr addrspace(1) %outData)`. Both definitions are correct, and the resulting LLVM IR is correct, but lowering stage of SPIR-V Backend fails to generate SPIR-V type.
```
typedef int myInt;
typedef struct {
int width;
int height;
} image_kernel_data;
struct struct_name {
int i;
int y;
};
void kernel foo(__global image_kernel_data* in,
__global struct struct_name *outData,
myInt out) {}
```
```
define spir_kernel void @foo(ptr addrspace(1) %in, i32 %out, ptr addrspace(1) %outData) ... !kernel_arg_type !7 ... {
entry:
ret void
}
...
!7 = !{!"image_kernel_data*", !"myInt", !"struct struct_name*"}
```
The PR changes a contract of `SPIRVType *getArgSPIRVType(...)` in a way that it may return `nullptr` to signal that the metadata string content is not recognized, so corresponding comments are added and a couple of checks for `nullptr` are inserted where appropriate.
>From 6f3fb5155c0b86a1386e6cbdc7e54ce95bfc6d5c Mon Sep 17 00:00:00 2001
From: "Levytskyy, Vyacheslav" <vyacheslav.levytskyy at intel.com>
Date: Fri, 19 Jan 2024 06:58:49 -0800
Subject: [PATCH] improve how lowering of formal arguments interprets a value
of 'kernel_arg_type'
---
llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp | 35 ++++++++++---------
llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp | 12 ++++---
llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h | 1 +
3 files changed, 27 insertions(+), 21 deletions(-)
diff --git a/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp b/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp
index 0a8b5499a1fc2ac..b6c151b1e73c856 100644
--- a/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp
@@ -209,23 +209,24 @@ static SPIRVType *getArgSPIRVType(const Function &F, unsigned ArgIdx,
isSpecialOpaqueType(OriginalArgType))
return GR->getOrCreateSPIRVType(OriginalArgType, MIRBuilder, ArgAccessQual);
- MDString *MDKernelArgType =
- getKernelArgAttribute(F, ArgIdx, "kernel_arg_type");
- if (!MDKernelArgType || (!MDKernelArgType->getString().ends_with("*") &&
- !MDKernelArgType->getString().ends_with("_t")))
- return GR->getOrCreateSPIRVType(OriginalArgType, MIRBuilder, ArgAccessQual);
-
- if (MDKernelArgType->getString().ends_with("*"))
- return GR->getOrCreateSPIRVTypeByName(
- MDKernelArgType->getString(), MIRBuilder,
- addressSpaceToStorageClass(OriginalArgType->getPointerAddressSpace()));
-
- if (MDKernelArgType->getString().ends_with("_t"))
- return GR->getOrCreateSPIRVTypeByName(
- "opencl." + MDKernelArgType->getString().str(), MIRBuilder,
- SPIRV::StorageClass::Function, ArgAccessQual);
-
- llvm_unreachable("Unable to recognize argument type name.");
+ SPIRVType *ResArgType = nullptr;
+ if (MDString *MDKernelArgType =
+ getKernelArgAttribute(F, ArgIdx, "kernel_arg_type")) {
+ StringRef MDTypeStr = MDKernelArgType->getString();
+ if (MDTypeStr.ends_with("*")) {
+ ResArgType = GR->getOrCreateSPIRVTypeByName(
+ MDTypeStr, MIRBuilder,
+ addressSpaceToStorageClass(
+ OriginalArgType->getPointerAddressSpace()));
+ } else if (MDTypeStr.ends_with("_t")) {
+ ResArgType = GR->getOrCreateSPIRVTypeByName(
+ "opencl." + MDTypeStr.str(), MIRBuilder,
+ SPIRV::StorageClass::Function, ArgAccessQual);
+ }
+ }
+ return ResArgType ? ResArgType
+ : GR->getOrCreateSPIRVType(OriginalArgType, MIRBuilder,
+ ArgAccessQual);
}
static bool isEntryPoint(const Function &F) {
diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
index 6c009b9e8ddefac..f2c27467c34b491 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
@@ -443,8 +443,9 @@ Register SPIRVGlobalRegistry::buildConstantSampler(
SPIRVType *SampTy;
if (SpvType)
SampTy = getOrCreateSPIRVType(getTypeForSPIRVType(SpvType), MIRBuilder);
- else
- SampTy = getOrCreateSPIRVTypeByName("opencl.sampler_t", MIRBuilder);
+ else if ((SampTy = getOrCreateSPIRVTypeByName("opencl.sampler_t",
+ MIRBuilder)) == nullptr)
+ report_fatal_error("Unable to recognize SPIRV type name: opencl.sampler_t");
auto Sampler =
ResReg.isValid()
@@ -941,6 +942,7 @@ SPIRVGlobalRegistry::checkSpecialInstr(const SPIRV::SpecialTypeDescriptor &TD,
return nullptr;
}
+// Returns nullptr if unable to recognize SPIRV type name
// TODO: maybe use tablegen to implement this.
SPIRVType *SPIRVGlobalRegistry::getOrCreateSPIRVTypeByName(
StringRef TypeStr, MachineIRBuilder &MIRBuilder,
@@ -992,8 +994,10 @@ SPIRVType *SPIRVGlobalRegistry::getOrCreateSPIRVTypeByName(
} else if (TypeStr.starts_with("double")) {
Ty = Type::getDoubleTy(Ctx);
TypeStr = TypeStr.substr(strlen("double"));
- } else
- llvm_unreachable("Unable to recognize SPIRV type name.");
+ } else {
+ // Unable to recognize SPIRV type name
+ return nullptr;
+ }
auto SpirvTy = getOrCreateSPIRVType(Ty, MIRBuilder, AQ);
diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
index 60967bfb68a87e3..f3280928c25dfab 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
@@ -138,6 +138,7 @@ class SPIRVGlobalRegistry {
// Either generate a new OpTypeXXX instruction or return an existing one
// corresponding to the given string containing the name of the builtin type.
+ // Return nullptr if unable to recognize SPIRV type name from `TypeStr`.
SPIRVType *getOrCreateSPIRVTypeByName(
StringRef TypeStr, MachineIRBuilder &MIRBuilder,
SPIRV::StorageClass::StorageClass SC = SPIRV::StorageClass::Function,
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