Skip to content

[llvm-c] Create a 128 bit floating point constant from 2 64 bit values #164381

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 4 commits into
base: main
Choose a base branch
from
Open

[llvm-c] Create a 128 bit floating point constant from 2 64 bit values #164381

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
624b310
Create a 128 bit floating point constant from 2 64 bit values
demoitem Oct 21, 2025
18e65e2
Update after review. Extend the function to accept the two 128 bit float
demoitem Oct 22, 2025
07e834c
Fix formatting
demoitem Oct 22, 2025
c1c5d61
Further changes per review
demoitem Nov 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 7 additions & 0 deletions llvm/include/llvm-c/Core.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2339,6 +2339,13 @@ LLVM_C_ABI LLVMValueRef LLVMConstRealOfStringAndSize(LLVMTypeRef RealTy,
const char *Text,
unsigned SLen);

/**
* Obtain a constant for a floating point FP128 value from 2 64 bit values.
* Only the LLVMFP128Type or LLVMPPCFP128Type are accepted.
*/

LLVM_C_ABI LLVMValueRef LLVMConstFP128(LLVMTypeRef Ty, const uint64_t N[2]);

/**
* Obtain the zero extended value for an integer constant value.
*
Expand Down
8 changes: 8 additions & 0 deletions llvm/lib/IR/Core.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1573,6 +1573,14 @@ LLVMValueRef LLVMConstRealOfStringAndSize(LLVMTypeRef RealTy, const char Str[],
return wrap(ConstantFP::get(unwrap(RealTy), StringRef(Str, SLen)));
}

LLVMValueRef LLVMConstFP128(LLVMTypeRef Ty, const uint64_t N[2]) {
Type *T = unwrap(Ty);
assert(T->getPrimitiveSizeInBits() == 128 && "Ty size should be 128");
Copy link
Contributor

@nikic nikic Oct 29, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
assert(T->getPrimitiveSizeInBits() == 128 && "Ty size should be 128");
assert(T->getScalarSizeInBits() == 128 && "Ty size should be 128");

To allow vector of float.

APInt AI(128, ArrayRef<uint64_t>(N, 2));
Copy link
Contributor

@nikic nikic Oct 29, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Rather than hardcoding 128 here, we can use the size of the float (e.g. via getScalarSizeInBits). The corresponding size of the array would be divideCeil(SizeInBits, 64). Then this would work for all sizes of floats.

APFloat Quad(T->getFltSemantics(), AI);
return wrap(ConstantFP::get(T, Quad));
}

unsigned long long LLVMConstIntGetZExtValue(LLVMValueRef ConstantVal) {
return unwrap<ConstantInt>(ConstantVal)->getZExtValue();
}
Expand Down
14 changes: 14 additions & 0 deletions llvm/unittests/IR/ConstantsTest.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -835,5 +835,19 @@ TEST(ConstantsTest, BlockAddressCAPITest) {
EXPECT_EQ(&BB, OutBB);
}

TEST(ConstantsTest, Float128Test) {
LLVMTypeRef Ty128 = LLVMFP128TypeInContext(LLVMGetGlobalContext());
LLVMTypeRef TyPPC128 = LLVMPPCFP128TypeInContext(LLVMGetGlobalContext());
LLVMBuilderRef Builder = LLVMCreateBuilder();
uint64_t n[2] = {0x4000000000000000, 0x0}; //+2
uint64_t m[2] = {0xC000000000000000, 0x0}; //-2
LLVMValueRef val1 = LLVMConstFP128(Ty128, n);
LLVMValueRef val2 = LLVMConstFP128(Ty128, m);
LLVMValueRef val3 = LLVMBuildFAdd(Builder, val1, val2, "test");
EXPECT_TRUE(val3 != nullptr);
LLVMValueRef val4 = LLVMConstFP128(TyPPC128, n);
EXPECT_TRUE(val4 != nullptr);
}

} // end anonymous namespace
} // end namespace llvm