[llvm] Draft: [DAGCombiner] Remove all `UnsafeFPMath` references (PR #146295)

[via llvm-commits]

https://github.com/paperchalice updated https://github.com/llvm/llvm-project/pull/146295

>From 5dda9d969699ed03538cdc65a56b3e4942aa9a5e Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Mon, 30 Jun 2025 09:14:24 +0800
Subject: [PATCH 1/3] remove `UnsafeFPMath` usages in `visitFADD`

---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8554db0a1220c..b8e1da4749540 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -17581,7 +17581,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
   // If 'unsafe math' or reassoc and nsz, fold lots of things.
   // TODO: break out portions of the transformations below for which Unsafe is
   //       considered and which do not require both nsz and reassoc
-  if (((Options.UnsafeFPMath && Options.NoSignedZerosFPMath) ||
+  if ((Options.NoSignedZerosFPMath ||
        (Flags.hasAllowReassociation() && Flags.hasNoSignedZeros())) &&
       AllowNewConst) {
     // fadd (fadd x, c1), c2 -> fadd x, c1 + c2
@@ -17668,7 +17668,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
     }
   } // enable-unsafe-fp-math && AllowNewConst
 
-  if (((Options.UnsafeFPMath && Options.NoSignedZerosFPMath) ||
+  if ((Options.NoSignedZerosFPMath ||
        (Flags.hasAllowReassociation() && Flags.hasNoSignedZeros()))) {
     // Fold fadd(vecreduce(x), vecreduce(y)) -> vecreduce(fadd(x, y))
     if (SDValue SD = reassociateReduction(ISD::VECREDUCE_FADD, ISD::FADD, DL,

>From 69ac7066ae492afb97c528669007189522f079ce Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Mon, 30 Jun 2025 09:30:51 +0800
Subject: [PATCH 2/3] Remove `UnsafeFPMath` in `visitFSUB`

---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b8e1da4749540..ebc553a57440e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -17771,7 +17771,7 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
     }
   }
 
-  if (((Options.UnsafeFPMath && Options.NoSignedZerosFPMath) ||
+  if ((Options.NoSignedZerosFPMath ||
        (Flags.hasAllowReassociation() && Flags.hasNoSignedZeros())) &&
       N1.getOpcode() == ISD::FADD) {
     // X - (X + Y) -> -Y

>From 8c3bc9ebab3809935a6580ef0e72d2131403ae68 Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Mon, 30 Jun 2025 09:32:17 +0800
Subject: [PATCH 3/3] Remove `UnsafeFPMath` in `visitFMUL`

---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ebc553a57440e..5d69f55e0d1df 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -17935,7 +17935,7 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
   if (SDValue NewSel = foldBinOpIntoSelect(N))
     return NewSel;
 
-  if (Options.UnsafeFPMath || Flags.hasAllowReassociation()) {
+  if (Flags.hasAllowReassociation()) {
     // fmul (fmul X, C1), C2 -> fmul X, C1 * C2
     if (DAG.isConstantFPBuildVectorOrConstantFP(N1) &&
         N0.getOpcode() == ISD::FMUL) {