From ede5ce93913e4f20f6112e251fab6a470bade1ea Mon Sep 17 00:00:00 2001
From: Marcin Juszkiewicz <mjuszkiewicz@redhat.com>
Date: Thu, 30 Jul 2026 10:46:45 +0200
Subject: [PATCH] Handle FMA on RISC-V

MathCore, Matrix tests fail on RISC-V:

266 - gtest-math-mathcore-stressMathCoreUnit (Failed)

Discrepancy in PtEtaPhiMVector operations() :
62919.12458590859 != 62919.124585843325 discr = 5   (Allowed discrepancy is 1.7763568394002505e-13)

300 - gtest-math-matrix-testMatrixTSparse (Failed)

Expected equality of these values:
  m1
    Which is: 80-byte object <90-0A 9E-93 FF-FF 00-00 00-00 00-00 00-00 00-02 04-00 00-00 05-00 00-00 01-00 00-00 00-00 00-00 14-00 00-00 05-00 00-00 00-00 00-00 00-00 B0-3C 01-E2 1E-94 FF-FF 00-00 30-26 61-55 55-55 00-00 00-62 60-55 55-55 00-00 A0-2B 61-55 55-55 00-00>
  m2
    Which is: 264-byte object <48-76 56-55 55-55 00-00 00-00 00-00 00-00 00-02 04-00 00-00 05-00 00-00 01-00 00-00 00-00 00-00 14-00 00-00 00-00 00-00 00-00 00-00 00-00 B0-3C 01-00 00-00 03-00 00-00 18-2D 44-54 FB-21 09-40 ... 53-B7 49-9E A1-B8 34-40 40-42 AC-EF 82-70 37-40 E0-09 61-55 55-55 00-00 60-E2 1E-94 FF-FF 00-00 50-2A 61-55 55-55 00-00 20-0A 61-55 55-55 00-00 30-E3 1E-94 FF-FF 00-00 60-E1 1E-94 FF-FF 00-00>

422 - test-stressmathcore (Failed)                      longtest

Based on my experience with similar failures on AArch64 (years ago) I
suspected FMA handling. Looked through code and found some places where
disabling/handling FMA was needed.
---
 math/mathcore/CMakeLists.txt                | 7 +++++++
 math/mathcore/test/stress/testGenVector.cxx | 3 ++-
 math/matrix/CMakeLists.txt                  | 7 +++++++
 math/matrix/test/CMakeLists.txt             | 6 ++++++
 test/stressMathCore.cxx                     | 3 ++-
 5 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/math/mathcore/CMakeLists.txt b/math/mathcore/CMakeLists.txt
index 6d88a65284ddc..319051e35335c 100644
--- a/math/mathcore/CMakeLists.txt
+++ b/math/mathcore/CMakeLists.txt
@@ -190,4 +190,11 @@ ROOT_STANDARD_LIBRARY_PACKAGE(MathCore
 
 target_link_libraries(MathCore PRIVATE ${CMAKE_THREAD_LIBS_INIT})
 
+# Force remove FMA on RISC-V
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64|riscv")
+  if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+    target_compile_options(MathCore PRIVATE -ffp-contract=off)
+  endif()
+endif()
+
 ROOT_ADD_TEST_SUBDIRECTORY(test)
diff --git a/math/mathcore/test/stress/testGenVector.cxx b/math/mathcore/test/stress/testGenVector.cxx
index f8b65a09444cd..1d3577dd75e29 100644
--- a/math/mathcore/test/stress/testGenVector.cxx
+++ b/math/mathcore/test/stress/testGenVector.cxx
@@ -79,7 +79,8 @@ TYPED_TEST_P(GenVectorTest, TestGenVectors)
    scale = this->fDim * 20;
    if (this->fDim == 3 && this->V2Name() == "RhoEtaPhiVector") scale *= 12; // for problem with RhoEtaPhi
    if (this->fDim == 4 && ( this->V2Name() == "PtEtaPhiMVector"  || this->V2Name() == "PxPyPzMVector")) {
-#if (defined(__arm__) || defined(__arm64__) || defined(__aarch64__) || defined(__s390x__) || defined(__FMA__))
+#if (defined(__arm__) || defined(__arm64__) || defined(__aarch64__) || defined(__s390x__) || defined(__FMA__)) || \
+   defined(__riscv)
       scale *= 1.E7;
 #else
       scale *= 10;
diff --git a/math/matrix/CMakeLists.txt b/math/matrix/CMakeLists.txt
index 64d7e20a6d135..e7ab970408d96 100644
--- a/math/matrix/CMakeLists.txt
+++ b/math/matrix/CMakeLists.txt
@@ -82,5 +82,12 @@ ROOT_STANDARD_LIBRARY_PACKAGE(Matrix
    -writeEmptyRootPCM
 )
 
+# Force remove FMA on RISC-V
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64|riscv")
+  if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+    target_compile_options(Matrix PRIVATE -ffp-contract=off)
+  endif()
+endif()
+
 ROOT_ADD_TEST_SUBDIRECTORY(test)
 
diff --git a/math/matrix/test/CMakeLists.txt b/math/matrix/test/CMakeLists.txt
index ec88d5deb9579..13a21be919d8c 100644
--- a/math/matrix/test/CMakeLists.txt
+++ b/math/matrix/test/CMakeLists.txt
@@ -5,5 +5,11 @@
 #For the list of contributors see $ROOTSYS / README / CREDITS.
 
 ROOT_ADD_GTEST(testMatrixTSparse testMatrixTSparse.cxx LIBRARIES Matrix)
+# Disable FMA on RISC-V to avoid 1-ULP differences between sparse and dense paths
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64|riscv")
+  if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+    target_compile_options(testMatrixTSparse PRIVATE -ffp-contract=off)
+  endif()
+endif()
 ROOT_ADD_GTEST(testMatrixTDecomp testMatrixTDecomp.cxx LIBRARIES Matrix)
 ROOT_ADD_GTEST(testMatrixT testMatrixT.cxx LIBRARIES Matrix)
\ No newline at end of file
diff --git a/test/stressMathCore.cxx b/test/stressMathCore.cxx
index 67b9d26dcb67d..467eb0c2ee8f8 100644
--- a/test/stressMathCore.cxx
+++ b/test/stressMathCore.cxx
@@ -1113,7 +1113,8 @@ int testVector(int ngen, bool testio=false) {
    scale = Dim*20;
    if (Dim==3 && VecType<V2>::name() == "RhoEtaPhiVector") scale *= 12; // for problem with RhoEtaPhi
    if (Dim==4 && ( VecType<V2>::name() == "PtEtaPhiMVector" || VecType<V2>::name() == "PxPyPzMVector")) {
-#if (defined(__arm__) || defined(__arm64__) || defined(__aarch64__) || defined(__s390x__) || defined(__FMA__))
+#if (defined(__arm__) || defined(__arm64__) || defined(__aarch64__) || defined(__s390x__) || defined(__FMA__)) || \
+   defined(__riscv)
       scale *= 1.E7;
 #else
       scale *= 10;