[llvm] [AArch64] Remove `UnsafeFPMath` (PR #150876)

[via llvm-commits]

https://github.com/paperchalice created https://github.com/llvm/llvm-project/pull/150876

We should always use fast math flags, remove these global flags incrementally.

>From 35a571c403b23b6d6e1d7dc0658917bfc6cd4125 Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Sat, 26 Jul 2025 18:00:16 +0800
Subject: [PATCH] [AArch64] Remove `UnsafeFPMath`

---
 llvm/lib/Target/AArch64/AArch64ISelLowering.cpp | 17 ++++++++---------
 llvm/lib/Target/AArch64/AArch64ISelLowering.h   |  2 +-
 llvm/lib/Target/AArch64/AArch64InstrInfo.cpp    |  8 +++-----
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 7b49754ee7e1f..4e11276cdf9d1 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -11325,7 +11325,7 @@ static SDValue emitFloatCompareMask(SDValue LHS, SDValue RHS, SDValue TVal,
 
 SDValue AArch64TargetLowering::LowerSELECT_CC(
     ISD::CondCode CC, SDValue LHS, SDValue RHS, SDValue TVal, SDValue FVal,
-    iterator_range<SDNode::user_iterator> Users, bool HasNoNaNs,
+    iterator_range<SDNode::user_iterator> Users, SDNodeFlags Flags,
     const SDLoc &DL, SelectionDAG &DAG) const {
   // Handle f128 first, because it will result in a comparison of some RTLIB
   // call result against zero.
@@ -11523,7 +11523,7 @@ SDValue AArch64TargetLowering::LowerSELECT_CC(
           return true;
         }
       })) {
-    bool NoNaNs = getTargetMachine().Options.NoNaNsFPMath || HasNoNaNs;
+    bool NoNaNs = getTargetMachine().Options.NoNaNsFPMath || Flags.hasNoNaNs();
     SDValue VectorCmp =
         emitFloatCompareMask(LHS, RHS, TVal, FVal, CC, NoNaNs, DL, DAG);
     if (VectorCmp)
@@ -11537,7 +11537,7 @@ SDValue AArch64TargetLowering::LowerSELECT_CC(
   AArch64CC::CondCode CC1, CC2;
   changeFPCCToAArch64CC(CC, CC1, CC2);
 
-  if (DAG.getTarget().Options.UnsafeFPMath) {
+  if (Flags.hasNoSignedZeros()) {
     // Transform "a == 0.0 ? 0.0 : x" to "a == 0.0 ? a : x" and
     // "a != 0.0 ? x : 0.0" to "a != 0.0 ? x : a" to avoid materializing 0.0.
     ConstantFPSDNode *RHSVal = dyn_cast<ConstantFPSDNode>(RHS);
@@ -11611,15 +11611,14 @@ SDValue AArch64TargetLowering::LowerVECTOR_SPLICE(SDValue Op,
 
 SDValue AArch64TargetLowering::LowerSELECT_CC(SDValue Op,
                                               SelectionDAG &DAG) const {
+  SDNodeFlags Flags = Op->getFlags();
   ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
   SDValue LHS = Op.getOperand(0);
   SDValue RHS = Op.getOperand(1);
   SDValue TVal = Op.getOperand(2);
   SDValue FVal = Op.getOperand(3);
-  bool HasNoNans = Op->getFlags().hasNoNaNs();
   SDLoc DL(Op);
-  return LowerSELECT_CC(CC, LHS, RHS, TVal, FVal, Op->users(), HasNoNans, DL,
-                        DAG);
+  return LowerSELECT_CC(CC, LHS, RHS, TVal, FVal, Op->users(), Flags, DL, DAG);
 }
 
 SDValue AArch64TargetLowering::LowerSELECT(SDValue Op,
@@ -11694,8 +11693,8 @@ SDValue AArch64TargetLowering::LowerSELECT(SDValue Op,
                                      DAG.getUNDEF(MVT::f32), FVal);
   }
 
-  SDValue Res =
-      LowerSELECT_CC(CC, LHS, RHS, TVal, FVal, Op->users(), HasNoNans, DL, DAG);
+  SDValue Res = LowerSELECT_CC(CC, LHS, RHS, TVal, FVal, Op->getFlags(),
+                               Op->users(), HasNoNans, DL, DAG);
 
   if ((Ty == MVT::f16 || Ty == MVT::bf16) && !Subtarget->hasFullFP16()) {
     return DAG.getTargetExtractSubreg(AArch64::hsub, DL, Ty, Res);
@@ -16674,7 +16673,7 @@ bool AArch64TargetLowering::isProfitableToHoist(Instruction *I) const {
   return !(isFMAFasterThanFMulAndFAdd(*F, Ty) &&
            isOperationLegalOrCustom(ISD::FMA, getValueType(DL, Ty)) &&
            (Options.AllowFPOpFusion == FPOpFusion::Fast ||
-            Options.UnsafeFPMath));
+            I->getFastMathFlags().allowContract()));
 }
 
 // All 32-bit GPR operations implicitly zero the high-half of the corresponding
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
index 95d0e3be70d16..ea63edd86210e 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -662,7 +662,7 @@ class AArch64TargetLowering : public TargetLowering {
   SDValue LowerSELECT_CC(ISD::CondCode CC, SDValue LHS, SDValue RHS,
                          SDValue TVal, SDValue FVal,
                          iterator_range<SDNode::user_iterator> Users,
-                         bool HasNoNans, const SDLoc &dl,
+                         SDNodeFlags Flags, const SDLoc &dl,
                          SelectionDAG &DAG) const;
   SDValue LowerINIT_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerADJUST_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const;
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index 8685d7a04ac9c..51e0c3d764abd 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -6574,8 +6574,7 @@ static bool isCombineInstrCandidateFP(const MachineInstr &Inst) {
     TargetOptions Options = Inst.getParent()->getParent()->getTarget().Options;
     // We can fuse FADD/FSUB with FMUL, if fusion is either allowed globally by
     // the target options or if FADD/FSUB has the contract fast-math flag.
-    return Options.UnsafeFPMath ||
-           Options.AllowFPOpFusion == FPOpFusion::Fast ||
+    return Options.AllowFPOpFusion == FPOpFusion::Fast ||
            Inst.getFlag(MachineInstr::FmContract);
     return true;
   }
@@ -6680,9 +6679,8 @@ bool AArch64InstrInfo::isAssociativeAndCommutative(const MachineInstr &Inst,
   case AArch64::FMUL_ZZZ_H:
   case AArch64::FMUL_ZZZ_S:
   case AArch64::FMUL_ZZZ_D:
-    return Inst.getParent()->getParent()->getTarget().Options.UnsafeFPMath ||
-           (Inst.getFlag(MachineInstr::MIFlag::FmReassoc) &&
-            Inst.getFlag(MachineInstr::MIFlag::FmNsz));
+    return Inst.getFlag(MachineInstr::MIFlag::FmReassoc) &&
+           Inst.getFlag(MachineInstr::MIFlag::FmNsz);
 
   // == Integer types ==
   // -- Base instructions --