[clang] [CIR] Added fast-math flags to LLVM intrinsic calls (PR #224899)
Kunal Dubey via cfe-commits
cfe-commits at lists.llvm.org
Sun Sep 20 02:10:19 PDT 2026
https://github.com/xakep8 created https://github.com/llvm/llvm-project/pull/224899
Added fast-math flags attribute to CIR which cir.call_llvm_intrinsic now carries through DirectToLLVM lowering. CIR now preserves fast-math flags such as reassoc when lowering to llvm.call_intrinsic.
Added test for the same.
>From 86288722d33eb011c4fa8238ebbaf4724e3654bc Mon Sep 17 00:00:00 2001
From: Kunal Dubey <xakep8 at protonmail.com>
Date: Sun, 20 Sep 2026 14:31:07 +0530
Subject: [PATCH] [CIR] Added fast-math flags to LLVM intrinsic calls
Added fast-math flags attribute to CIR which cir.call_llvm_intrinsic now
carries through DirectToLLVM lowering. CIR now preserves fast-math flags
such as reassoc when lowering to llvm.call_intrinsic.
Added test for the same.
---
.../include/clang/CIR/Dialect/IR/CIRAttrs.td | 28 +++++++++++++++++++
clang/include/clang/CIR/Dialect/IR/CIROps.td | 9 ++++--
clang/lib/CIR/CodeGen/CIRGenBuilder.h | 9 ++++++
.../CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp | 26 ++++++++++++++++-
.../test/CIR/Lowering/call-llvm-intrinsic.cir | 11 ++++++++
5 files changed, 80 insertions(+), 3 deletions(-)
diff --git a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
index c5f19592d4592..9445badd9f2a1 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
@@ -947,6 +947,34 @@ def CIR_FenvAttr : CIR_Attr<"Fenv", "fenv"> {
let canHaveIllegalCXXABIType = 0;
}
+//===----------------------------------------------------------------------===//
+// FastMathFlagsAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_FMFnone : I32BitEnumAttrCaseNone<"none">;
+def CIR_FMFnnan : I32BitEnumAttrCaseBit<"nnan", 0>;
+def CIR_FMFninf : I32BitEnumAttrCaseBit<"ninf", 1>;
+def CIR_FMFnsz : I32BitEnumAttrCaseBit<"nsz", 2>;
+def CIR_FMFarcp : I32BitEnumAttrCaseBit<"arcp", 3>;
+def CIR_FMFcontract : I32BitEnumAttrCaseBit<"contract", 4>;
+def CIR_FMFafn : I32BitEnumAttrCaseBit<"afn", 5>;
+def CIR_FMFreassoc : I32BitEnumAttrCaseBit<"reassoc", 6>;
+def CIR_FMFfast : I32BitEnumAttrCaseGroup<"fast", [
+ CIR_FMFnnan, CIR_FMFninf, CIR_FMFnsz, CIR_FMFarcp, CIR_FMFcontract,
+ CIR_FMFafn, CIR_FMFreassoc
+]>;
+
+def CIR_FastMathFlags : CIR_I32BitEnum<
+ "FastMathFlags", "fast-math flags", [
+ CIR_FMFnone, CIR_FMFnnan, CIR_FMFninf, CIR_FMFnsz, CIR_FMFarcp,
+ CIR_FMFcontract, CIR_FMFafn, CIR_FMFreassoc, CIR_FMFfast
+]> {
+ let separator = ", ";
+ let printBitEnumPrimaryGroups = 1;
+}
+
+def CIR_FastMathFlagsAttr : CIR_EnumAttr<CIR_FastMathFlags, "fastmath">;
+
//===----------------------------------------------------------------------===//
// GlobalViewAttr
//===----------------------------------------------------------------------===//
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index f23475842ed3a..16fd5758c8fb7 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -4467,7 +4467,9 @@ def CIR_LLVMIntrinsicCallOp : CIR_Op<"call_llvm_intrinsic"> {
let results = (outs Optional<CIR_AnyType>:$result);
let arguments = (ins
- StrAttr:$intrinsic_name, Variadic<CIR_AnyType>:$arg_ops);
+ StrAttr:$intrinsic_name,
+ OptionalAttr<CIR_FastMathFlagsAttr>:$fastmath_flags,
+ Variadic<CIR_AnyType>:$arg_ops);
let skipDefaultBuilders = 1;
@@ -4477,8 +4479,11 @@ def CIR_LLVMIntrinsicCallOp : CIR_Op<"call_llvm_intrinsic"> {
let builders = [
OpBuilder<(ins "mlir::StringAttr":$intrinsic_name, "mlir::Type":$resType,
- CArg<"mlir::ValueRange", "{}">:$operands), [{
+ CArg<"mlir::ValueRange", "{}">:$operands,
+ CArg<"cir::FastMathFlagsAttr", "{}">:$fastmath), [{
$_state.addAttribute("intrinsic_name", intrinsic_name);
+ if (fastmath)
+ $_state.addAttribute("fastmath_flags", fastmath);
$_state.addOperands(operands);
if (resType)
$_state.addTypes(resType);
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
index 91e3b18a6b315..2f82c1d249434 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuilder.h
+++ b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -830,6 +830,15 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
std::forward<Operands>(op)...)
.getResult();
}
+
+ mlir::Value emitIntrinsicCallOp(mlir::Location loc, const llvm::StringRef str,
+ const mlir::Type &resTy,
+ mlir::ValueRange operands,
+ cir::FastMathFlagsAttr fastmath) {
+ return cir::LLVMIntrinsicCallOp::create(
+ *this, loc, this->getStringAttr(str), resTy, operands, fastmath)
+ .getResult();
+ }
};
} // namespace clang::CIRGen
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index f29fa93ee4609..2d816015c3537 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -581,6 +581,27 @@ mlir::LogicalResult lowerConstrainableFPOp(
constrainedMnemonic, hasRoundingMode);
}
+static mlir::LLVM::FastmathFlags
+convertFastMathFlags(cir::FastMathFlags cirFlags) {
+ mlir::LLVM::FastmathFlags llvmFlags{};
+ const std::pair<cir::FastMathFlags, mlir::LLVM::FastmathFlags> flags[] = {
+ {cir::FastMathFlags::nnan, mlir::LLVM::FastmathFlags::nnan},
+ {cir::FastMathFlags::ninf, mlir::LLVM::FastmathFlags::ninf},
+ {cir::FastMathFlags::nsz, mlir::LLVM::FastmathFlags::nsz},
+ {cir::FastMathFlags::arcp, mlir::LLVM::FastmathFlags::arcp},
+ {cir::FastMathFlags::contract, mlir::LLVM::FastmathFlags::contract},
+ {cir::FastMathFlags::afn, mlir::LLVM::FastmathFlags::afn},
+ {cir::FastMathFlags::reassoc, mlir::LLVM::FastmathFlags::reassoc},
+ };
+
+ for (auto [cirFlag, llvmFlag] : flags) {
+ if (bitEnumContainsAny(cirFlags, cirFlag))
+ llvmFlags = llvmFlags | llvmFlag;
+ }
+
+ return llvmFlags;
+}
+
mlir::LogicalResult CIRToLLVMLLVMIntrinsicCallOpLowering::matchAndRewrite(
cir::LLVMIntrinsicCallOp op, OpAdaptor adaptor,
mlir::ConversionPatternRewriter &rewriter) const {
@@ -593,6 +614,9 @@ mlir::LogicalResult CIRToLLVMLLVMIntrinsicCallOpLowering::matchAndRewrite(
return op.emitError("expected LLVM result type");
}
StringRef name = op.getIntrinsicName();
+ mlir::LLVM::FastmathFlags fastmathFlags = {};
+ if (std::optional<cir::FastMathFlags> fastmath = op.getFastmathFlags())
+ fastmathFlags = convertFastMathFlags(*fastmath);
// Some LLVM intrinsics require ElementType attribute to be attached to
// the argument of pointer type. That prevents us from generating LLVM IR
@@ -605,7 +629,7 @@ mlir::LogicalResult CIRToLLVMLLVMIntrinsicCallOpLowering::matchAndRewrite(
// to set LLVM IR attribute.
assert(!cir::MissingFeatures::intrinsicElementTypeSupport());
replaceOpWithCallLLVMIntrinsicOp(rewriter, op, "llvm." + name, llvmResTy,
- adaptor.getOperands());
+ adaptor.getOperands(), fastmathFlags);
return mlir::success();
}
diff --git a/clang/test/CIR/Lowering/call-llvm-intrinsic.cir b/clang/test/CIR/Lowering/call-llvm-intrinsic.cir
index edd492aa7477c..643e4db0d7d0c 100644
--- a/clang/test/CIR/Lowering/call-llvm-intrinsic.cir
+++ b/clang/test/CIR/Lowering/call-llvm-intrinsic.cir
@@ -5,6 +5,8 @@
// 0-result (void) calls in addition to the single-result case.
!s32i = !cir.int<s, 32>
+!f32 = !cir.float
+!v4f32 = !cir.vector<4 x !f32>
module {
// 0-result, 0-operand.
@@ -24,4 +26,13 @@ module {
cir.call_llvm_intrinsic "amdgcn.s.sleep" %arg0 : (!s32i) -> ()
cir.return
}
+
+ // Fast-math flags are preserved on the lowered LLVM intrinsic call.
+ // CHECK-LABEL: llvm.func @fastmath_flags
+ // CHECK: llvm.call_intrinsic "llvm.vector.reduce.fadd"(%{{.*}}, %{{.*}}) {fastmathFlags = #llvm.fastmath<reassoc>} : (f32, vector<4xf32>) -> f32
+ // CHECK: llvm.return
+ cir.func @fastmath_flags(%arg0: !f32, %arg1: !v4f32) -> !f32 {
+ %0 = cir.call_llvm_intrinsic "vector.reduce.fadd" %arg0, %arg1 : (!f32, !v4f32) -> !f32 {fastmath_flags = #cir.fastmath<reassoc>}
+ cir.return %0 : !f32
+ }
}
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