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[SimplifyLibCalls] Constant fold nan libcall (#101459)
Reference: https://en.cppreference.com/w/c/numeric/math/nan The logic is copied from clang frontend: https://github.com/llvm/llvm-project/blob/1d2b2d29d733200b704f38d220d22ecc07d6cf42/clang/lib/AST/ExprConstant.cpp#L14741-L14777 --------- Co-authored-by: Nikita Popov <[email protected]>
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‎llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

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@@ -3858,6 +3858,22 @@ Value *LibCallSimplifier::optimizeStringMemoryLibCall(CallInst *CI,
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return nullptr;
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}
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/// Constant folding nan/nanf/nanl.
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static Value *optimizeNaN(CallInst *CI) {
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StringRef CharSeq;
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if (!getConstantStringInfo(CI->getArgOperand(0), CharSeq))
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return nullptr;
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APInt Fill;
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// Treat empty strings as if they were zero.
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if (CharSeq.empty())
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Fill = APInt(32, 0);
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else if (CharSeq.getAsInteger(0, Fill))
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return nullptr;
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return ConstantFP::getQNaN(CI->getType(), /*Negative=*/false, &Fill);
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}
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Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
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LibFunc Func,
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IRBuilderBase &Builder) {
@@ -3972,6 +3988,10 @@ Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
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case LibFunc_remquof:
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case LibFunc_remquol:
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return optimizeRemquo(CI, Builder);
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case LibFunc_nan:
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case LibFunc_nanf:
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case LibFunc_nanl:
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return optimizeNaN(CI);
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default:
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return nullptr;
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}

‎llvm/test/Transforms/InstCombine/nan.ll

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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@empty = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
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@dec = private unnamed_addr constant [2 x i8] c"1\00", align 1
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@hex = private unnamed_addr constant [4 x i8] c"0xf\00", align 1
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define double @nan_empty() {
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; CHECK-LABEL: define double @nan_empty() {
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; CHECK-NEXT: ret double 0x7FF8000000000000
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;
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%res = call double @nan(ptr @empty)
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ret double %res
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}
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define double @nan_dec() {
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; CHECK-LABEL: define double @nan_dec() {
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; CHECK-NEXT: ret double 0x7FF8000000000001
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;
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%res = call double @nan(ptr @dec)
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ret double %res
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}
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define double @nan_hex() {
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; CHECK-LABEL: define double @nan_hex() {
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; CHECK-NEXT: ret double 0x7FF800000000000F
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;
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%res = call double @nan(ptr @hex)
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ret double %res
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}
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define float @nanf_empty() {
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; CHECK-LABEL: define float @nanf_empty() {
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; CHECK-NEXT: ret float 0x7FF8000000000000
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;
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%res = call float @nanf(ptr @empty)
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ret float %res
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}
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; nagative tests
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define double @nan_poison() {
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; CHECK-LABEL: define double @nan_poison() {
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; CHECK-NEXT: [[RES:%.*]] = call double @nan(ptr poison)
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; CHECK-NEXT: ret double [[RES]]
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;
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%res = call double @nan(ptr poison)
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ret double %res
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}
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define double @nan_undef() {
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; CHECK-LABEL: define double @nan_undef() {
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; CHECK-NEXT: [[RES:%.*]] = call double @nan(ptr undef)
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; CHECK-NEXT: ret double [[RES]]
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;
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%res = call double @nan(ptr undef)
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ret double %res
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}
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define double @nan_null() {
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; CHECK-LABEL: define double @nan_null() {
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; CHECK-NEXT: [[RES:%.*]] = call double @nan(ptr null)
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; CHECK-NEXT: ret double [[RES]]
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;
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%res = call double @nan(ptr null)
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ret double %res
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}
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define double @nan_non_constant(ptr %x) {
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; CHECK-LABEL: define double @nan_non_constant(
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; CHECK-SAME: ptr [[X:%.*]]) {
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; CHECK-NEXT: [[RES:%.*]] = call double @nan(ptr [[X]])
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; CHECK-NEXT: ret double [[RES]]
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;
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%res = call double @nan(ptr %x)
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ret double %res
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}
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declare float @nanf(ptr)
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declare double @nan(ptr)

‎llvm/test/Transforms/InstCombine/nanl-fp128.ll

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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@empty = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
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@dec = private unnamed_addr constant [2 x i8] c"1\00", align 1
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@hex = private unnamed_addr constant [4 x i8] c"0xf\00", align 1
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define fp128 @nanl_empty() {
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; CHECK-LABEL: define fp128 @nanl_empty() {
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; CHECK-NEXT: ret fp128 0xL00000000000000007FFF800000000000
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;
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%res = call fp128 @nanl(ptr @empty)
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ret fp128 %res
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}
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define fp128 @nanl_dec() {
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; CHECK-LABEL: define fp128 @nanl_dec() {
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; CHECK-NEXT: ret fp128 0xL00000000000000017FFF800000000000
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;
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%res = call fp128 @nanl(ptr @dec)
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ret fp128 %res
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}
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define fp128 @nanl_hex() {
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; CHECK-LABEL: define fp128 @nanl_hex() {
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; CHECK-NEXT: ret fp128 0xL000000000000000F7FFF800000000000
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;
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%res = call fp128 @nanl(ptr @hex)
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ret fp128 %res
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}
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declare fp128 @nanl(ptr)

‎llvm/test/Transforms/InstCombine/nanl-fp80.ll

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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@empty = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
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@dec = private unnamed_addr constant [2 x i8] c"1\00", align 1
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@hex = private unnamed_addr constant [4 x i8] c"0xf\00", align 1
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define x86_fp80 @nanl_empty() {
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; CHECK-LABEL: define x86_fp80 @nanl_empty() {
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; CHECK-NEXT: ret x86_fp80 0xK7FFFC000000000000000
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;
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%res = call x86_fp80 @nanl(ptr @empty)
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ret x86_fp80 %res
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}
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define x86_fp80 @nanl_dec() {
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; CHECK-LABEL: define x86_fp80 @nanl_dec() {
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; CHECK-NEXT: ret x86_fp80 0xK7FFFC000000000000001
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;
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%res = call x86_fp80 @nanl(ptr @dec)
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ret x86_fp80 %res
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}
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define x86_fp80 @nanl_hex() {
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; CHECK-LABEL: define x86_fp80 @nanl_hex() {
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; CHECK-NEXT: ret x86_fp80 0xK7FFFC00000000000000F
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;
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%res = call x86_fp80 @nanl(ptr @hex)
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ret x86_fp80 %res
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}
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declare x86_fp80 @nanl(ptr)

‎llvm/test/Transforms/InstCombine/nanl-ppc-fp128.ll

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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@empty = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
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@dec = private unnamed_addr constant [2 x i8] c"1\00", align 1
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@hex = private unnamed_addr constant [4 x i8] c"0xf\00", align 1
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define ppc_fp128 @nanl_empty() {
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; CHECK-LABEL: define ppc_fp128 @nanl_empty() {
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; CHECK-NEXT: ret ppc_fp128 0xM7FF80000000000000000000000000000
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;
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%res = call ppc_fp128 @nanl(ptr @empty)
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ret ppc_fp128 %res
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}
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define ppc_fp128 @nanl_dec() {
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; CHECK-LABEL: define ppc_fp128 @nanl_dec() {
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; CHECK-NEXT: ret ppc_fp128 0xM7FF80000000000010000000000000000
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;
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%res = call ppc_fp128 @nanl(ptr @dec)
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ret ppc_fp128 %res
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}
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define ppc_fp128 @nanl_hex() {
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; CHECK-LABEL: define ppc_fp128 @nanl_hex() {
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; CHECK-NEXT: ret ppc_fp128 0xM7FF800000000000F0000000000000000
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;
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%res = call ppc_fp128 @nanl(ptr @hex)
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ret ppc_fp128 %res
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}
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declare ppc_fp128 @nanl(ptr)

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