https://github.com/choikwa updated
https://github.com/llvm/llvm-project/pull/129347
>From adfb9c08cf1d62cd2c6596520e65ef9f299d3cdc Mon Sep 17 00:00:00 2001
From: Kevin Choi <kevin.c...@amd.com>
Date: Fri, 28 Feb 2025 16:52:03 -0600
Subject: [PATCH] [AMDGPU][clang] provide device implementation for
__builtin_logb and __builtin_scalbn
Clang generates library calls for __builtin_* functions which can be a problem
for GPUs that cannot handle them.
This patch generates a device implementations for __builtin_logb and
__builtin_scalbn.
---
clang/lib/CodeGen/CGBuiltin.cpp | 43 ++++++++++++++++++++++++++-
clang/lib/CodeGen/CodeGenModule.h | 5 ++++
clang/test/CodeGenHIP/logb_scalbn.hip | 42 ++++++++++++++++++++++++++
3 files changed, 89 insertions(+), 1 deletion(-)
create mode 100644 clang/test/CodeGenHIP/logb_scalbn.hip
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index a5ed2595bad4d..5957fec364ae4 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -6621,10 +6621,27 @@ RValue CodeGenFunction::EmitBuiltinExpr(const
GlobalDecl GD, unsigned BuiltinID,
}
}
+ // These will be emitted as Intrinsic later.
+ auto NeedsDeviceOverloadToIntrin = [&](unsigned BuiltinID) {
+ if (getTarget().getTriple().isAMDGCN()) {
+ switch (BuiltinID) {
+ default:
+ return false;
+ case Builtin::BIlogb:
+ case Builtin::BI__builtin_logb:
+ case Builtin::BIscalbn:
+ case Builtin::BI__builtin_scalbn:
+ return true;
+ }
+ }
+ return false;
+ };
+
// If this is an alias for a lib function (e.g. __builtin_sin), emit
// the call using the normal call path, but using the unmangled
// version of the function name.
- if (getContext().BuiltinInfo.isLibFunction(BuiltinID))
+ if (!NeedsDeviceOverloadToIntrin(BuiltinID) &&
+ getContext().BuiltinInfo.isLibFunction(BuiltinID))
return emitLibraryCall(*this, FD, E,
CGM.getBuiltinLibFunction(FD, BuiltinID));
@@ -20910,6 +20927,30 @@ Value *CodeGenFunction::EmitAMDGPUBuiltinExpr(unsigned
BuiltinID,
case AMDGPU::BI__builtin_amdgcn_s_prefetch_data:
return emitBuiltinWithOneOverloadedType<2>(
*this, E, Intrinsic::amdgcn_s_prefetch_data);
+ case Builtin::BIlogb:
+ case Builtin::BI__builtin_logb: {
+ auto Src0 = EmitScalarExpr(E->getArg(0));
+ auto FrExpFunc = CGM.getIntrinsic(Intrinsic::amdgcn_frexp_exp,
+ {Builder.getInt32Ty(), Src0->getType()});
+ auto FrExp = Builder.CreateCall(FrExpFunc, Src0);
+ auto Add = Builder.CreateAdd(
+ FrExp, ConstantInt::getSigned(FrExp->getType(), -1), "", false, true);
+ auto SIToFP = Builder.CreateSIToFP(Add, Builder.getDoubleTy());
+ auto Fabs = emitBuiltinWithOneOverloadedType<1>(*this, E, Intrinsic::fabs);
+ auto FCmpONE = Builder.CreateFCmpONE(
+ Fabs, ConstantFP::getInfinity(Builder.getDoubleTy()));
+ auto Sel1 = Builder.CreateSelect(FCmpONE, SIToFP, Fabs);
+ auto FCmpOEQ =
+ Builder.CreateFCmpOEQ(Src0,
ConstantFP::getZero(Builder.getDoubleTy()));
+ auto Sel2 = Builder.CreateSelect(
+ FCmpOEQ, ConstantFP::getInfinity(Builder.getDoubleTy(), /*Neg*/ true),
+ Sel1);
+ return Sel2;
+ }
+ case Builtin::BIscalbn:
+ case Builtin::BI__builtin_scalbn:
+ return emitBinaryExpMaybeConstrainedFPBuiltin(
+ *this, E, Intrinsic::ldexp, Intrinsic::experimental_constrained_ldexp);
default:
return nullptr;
}
diff --git a/clang/lib/CodeGen/CodeGenModule.h
b/clang/lib/CodeGen/CodeGenModule.h
index 6deb467b2cc9f..ae1441dc3d009 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1231,6 +1231,11 @@ class CodeGenModule : public CodeGenTypeCache {
llvm::FunctionType *FnType = nullptr, bool DontDefer = false,
ForDefinition_t IsForDefinition = NotForDefinition);
+ /// Given a builtin id for a function, return a Function* for device
+ /// overload implementation.
+ llvm::Constant *getDeviceLibFunction(const FunctionDecl *FD,
+ unsigned BuiltinID);
+
/// Given a builtin id for a function like "__builtin_fabsf", return a
/// Function* for "fabsf".
llvm::Constant *getBuiltinLibFunction(const FunctionDecl *FD,
diff --git a/clang/test/CodeGenHIP/logb_scalbn.hip
b/clang/test/CodeGenHIP/logb_scalbn.hip
new file mode 100644
index 0000000000000..935941bb25939
--- /dev/null
+++ b/clang/test/CodeGenHIP/logb_scalbn.hip
@@ -0,0 +1,42 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
UTC_ARGS: --version 5
+// RUN: %clang --cuda-device-only -nogpuinc -nogpulib -emit-llvm -S -o - %s |
FileCheck %s
+#include <math.h>
+#define __device__ __attribute__((device))
+
+// CHECK-LABEL: define hidden void @_Z9my_kernelv(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[D1:%.*]] = alloca float, align 4, addrspace(5)
+// CHECK-NEXT: [[D2:%.*]] = alloca float, align 4, addrspace(5)
+// CHECK-NEXT: [[D3:%.*]] = alloca float, align 4, addrspace(5)
+// CHECK-NEXT: [[D4:%.*]] = alloca float, align 4, addrspace(5)
+// CHECK-NEXT: [[D1_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[D1]] to
ptr
+// CHECK-NEXT: [[D2_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[D2]] to
ptr
+// CHECK-NEXT: [[D3_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[D3]] to
ptr
+// CHECK-NEXT: [[D4_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[D4]] to
ptr
+// CHECK-NEXT: [[TMP0:%.*]] = call i32
@llvm.amdgcn.frexp.exp.i32.f64(double 1.600000e+01)
+// CHECK-NEXT: [[TMP1:%.*]] = add nsw i32 [[TMP0]], -1
+// CHECK-NEXT: [[TMP2:%.*]] = sitofp i32 [[TMP1]] to double
+// CHECK-NEXT: [[TMP3:%.*]] = call contract double @llvm.fabs.f64(double
1.600000e+01)
+// CHECK-NEXT: [[TMP4:%.*]] = fcmp contract one double [[TMP3]],
0x7FF0000000000000
+// CHECK-NEXT: [[TMP5:%.*]] = select contract i1 [[TMP4]], double [[TMP2]],
double [[TMP3]]
+// CHECK-NEXT: [[TMP6:%.*]] = select contract i1 false, double
0xFFF0000000000000, double [[TMP5]]
+// CHECK-NEXT: [[CONV:%.*]] = fptrunc contract double [[TMP6]] to float
+// CHECK-NEXT: store float [[CONV]], ptr [[D1_ASCAST]], align 4
+// CHECK-NEXT: [[CALL:%.*]] = call contract noundef float @_ZSt4logbf(float
noundef 1.600000e+01) #[[ATTR3:[0-9]+]]
+// CHECK-NEXT: store float [[CALL]], ptr [[D2_ASCAST]], align 4
+// CHECK-NEXT: [[TMP7:%.*]] = call contract double
@llvm.ldexp.f64.i32(double 1.600000e+01, i32 10)
+// CHECK-NEXT: [[CONV1:%.*]] = fptrunc contract double [[TMP7]] to float
+// CHECK-NEXT: store float [[CONV1]], ptr [[D3_ASCAST]], align 4
+// CHECK-NEXT: [[CALL2:%.*]] = call contract noundef float
@_ZSt6scalbnfi(float noundef 9.000000e+00, i32 noundef 4) #[[ATTR3]]
+// CHECK-NEXT: store float [[CALL2]], ptr [[D4_ASCAST]], align 4
+// CHECK-NEXT: ret void
+//
+__device__ void my_kernel(){
+
+ float D1 = __builtin_logb((float)16);
+ float D2 = logb((float)16);
+ float D3 = __builtin_scalbn((float)16, 10);
+ float D4 = scalbn((float)9.0, 4);
+}
+
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