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Add support for __nvvm_reflect changes in libdevice in CUDA-7.0

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Summary:
CUDA 7.0's libdevice uses slightly different IR to call __nvvm_reflect
and that triggers an assertion in nvvm_reflect optimization pass. This
change allows nvvm_reflect pass to deal with both old and new ways to
pass an argument to __nvvm_reflect.

Test Plan: ninja check-all

Reviewers: eliben, echristo

Subscribers: jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D8399

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232732 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Artem Belevich 2015-03-19 17:05:35 +00:00
parent a7c5163281
commit 97f4d01ee1
2 changed files with 63 additions and 5 deletions
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37
lib/Target/NVPTX/NVVMReflect.cpp
View File

@ -137,6 +137,26 @@ bool NVVMReflect::handleFunction(Function *ReflectFunction) {
// ConstantArray can be found successfully, see if it can be
// found in VarMap. If so, replace the uses of CallInst with the
// value found in VarMap. If not, replace the use with value 0.
// IR for __nvvm_reflect calls differs between CUDA versions:
// CUDA 6.5 and earlier uses this sequence:
// %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8
// (i8 addrspace(4)* getelementptr inbounds
// ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0))
// %reflect = tail call i32 @__nvvm_reflect(i8* %ptr)
//
// Value returned by Sym->getOperand(0) is a Constant with a
// ConstantDataSequential operand which can be converted to string and used
// for lookup.
//
// CUDA 7.0 does it slightly differently:
// %reflect = call i32 @__nvvm_reflect(i8* addrspacecast
// (i8 addrspace(1)* getelementptr inbounds
// ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*))
//
// In this case, we get a Constant with a GlobalVariable operand and we need
// to dig deeper to find its initializer with the string we'll use for lookup.
for (User *U : ReflectFunction->users()) {
assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
CallInst *Reflect = cast<CallInst>(U);
@ -158,16 +178,23 @@ bool NVVMReflect::handleFunction(Function *ReflectFunction) {
const Value *Sym = GEP->getOperand(0);
assert(isa<Constant>(Sym) && "Format of _reflect function not recognized");
const Constant *SymStr = cast<Constant>(Sym);
const Value *Operand = cast<Constant>(Sym)->getOperand(0);
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) {
// For CUDA-7.0 style __nvvm_reflect calls we need to find operand's
// initializer.
assert(GV->hasInitializer() &&
"Format of _reflect function not recognized");
const Constant *Initializer = GV->getInitializer();
Operand = Initializer;
}
assert(isa<ConstantDataSequential>(SymStr->getOperand(0)) &&
assert(isa<ConstantDataSequential>(Operand) &&
"Format of _reflect function not recognized");
assert(cast<ConstantDataSequential>(SymStr->getOperand(0))->isCString() &&
assert(cast<ConstantDataSequential>(Operand)->isCString() &&
"Format of _reflect function not recognized");
std::string ReflectArg =
cast<ConstantDataSequential>(SymStr->getOperand(0))->getAsString();
cast<ConstantDataSequential>(Operand)->getAsString();
ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");

31
test/CodeGen/NVPTX/nvvm-reflect.ll
View File

@ -46,3 +46,34 @@ define i32 @intrinsic() {
%reflect = tail call i32 @llvm.nvvm.reflect.p0i8(i8* %ptr)
ret i32 %reflect
}
; CUDA-7.0 passes __nvvm_reflect argument slightly differently.
; Verify that it works, too
@"$str" = private addrspace(1) constant [8 x i8] c"USE_MUL\00"
define float @bar(float %a, float %b) {
; USE_MUL_0: define float @bar
; USE_MUL_0-NOT: call i32 @__nvvm_reflect
; USE_MUL_1: define float @bar
; USE_MUL_1-NOT: call i32 @__nvvm_reflect
%reflect = call i32 @__nvvm_reflect(i8* addrspacecast (i8 addrspace(1)* getelementptr inbounds ([8 x i8], [8 x i8] addrspace(1)* @"$str", i32 0, i32 0) to i8*))
%cmp = icmp ne i32 %reflect, 0
br i1 %cmp, label %use_mul, label %use_add
use_mul:
; USE_MUL_1: fmul float %a, %b
; USE_MUL_0-NOT: fadd float %a, %b
%ret1 = fmul float %a, %b
br label %exit
use_add:
; USE_MUL_0: fadd float %a, %b
; USE_MUL_1-NOT: fmul float %a, %b
%ret2 = fadd float %a, %b
br label %exit
exit:
%ret = phi float [%ret1, %use_mul], [%ret2, %use_add]
ret float %ret
}