From 91172bd36927e9444ee9e9c80e489a1e6a13c72e Mon Sep 17 00:00:00 2001
From: Cameron McInally <cmcinally@nvidia.com>
Date: Wed, 22 Feb 2023 10:36:11 -0800
Subject: [PATCH] [DAGCombine] Fix an ICE in combineMinNumMaxNum(...)

65420c8041f4 introduced an ICE in combineMinNumMaxNum(...) when
combineMinNumMaxNumImpl(...) returns an SDValue(). Make sure to check that a
value is returned before trying to perform an FNEG on it.

GitHub Issue: #60924

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D144571

(cherry picked from commit af4c4f4e21434ae306b7ee83691b5a8c2d90e576)
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  3 ++-
 .../X86/2023-02-22-combineMinNumMaxNum.ll     | 20 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/X86/2023-02-22-combineMinNumMaxNum.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 0a3ebd73d2722..355a793ead482 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10447,7 +10447,8 @@ SDValue DAGCombiner::combineMinNumMaxNum(const SDLoc &DL, EVT VT, SDValue LHS,
       if (NegRHS == False) {
         SDValue Combined = combineMinNumMaxNumImpl(DL, VT, LHS, RHS, NegTrue,
                                                    False, CC, TLI, DAG);
-        return DAG.getNode(ISD::FNEG, DL, VT, Combined);
+        if (Combined)
+          return DAG.getNode(ISD::FNEG, DL, VT, Combined);
       }
     }
   }
diff --git a/llvm/test/CodeGen/X86/2023-02-22-combineMinNumMaxNum.ll b/llvm/test/CodeGen/X86/2023-02-22-combineMinNumMaxNum.ll
new file mode 100644
index 0000000000000..8b53d599393b9
--- /dev/null
+++ b/llvm/test/CodeGen/X86/2023-02-22-combineMinNumMaxNum.ll
@@ -0,0 +1,20 @@
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=skylake
+
+; Checking for a DAGCombine ICE.
+
+define float @test_combinemaxnum(float %sub) #0 {
+L.entry:
+  %maxnum1 = call float @llvm.maxnum.f32(float 0.000000e+00, float 0.000000e+00)
+  br label %L.LB21_850
+
+L.LB21_850:
+  %neg1 = fneg fast float %maxnum1
+  %neg2 = fneg fast float %sub
+  %mask = fcmp fast ule float %maxnum1, %neg2
+  %maxnum2 = select i1 %mask, float %neg1, float %sub
+  ret float %maxnum2
+}
+
+declare float @llvm.maxnum.f32(float, float) 
+
+attributes #0 = { "no-nans-fp-math"="true" "no-signed-zeros-fp-math"="true" }