[X86] Set default rounding mode round to nearest for llvm.set.rounding

[JaydeepChauhan14]

• Fix [X86][GlobalISel] Added support for llvm.set.rounding #156591 (comment)
• As per https://cdrdv2.intel.com/v1/dl/getContent/671200 default rounding mode is round to nearest.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: None (JaydeepChauhan14)

Changes

• Fix [X86][GlobalISel] Added support for llvm.set.rounding #156591 (comment)
• As per https://cdrdv2.intel.com/v1/dl/getContent/671200 default rounding mode is round to nearest.

---

Full diff: https://github.com/llvm/llvm-project/pull/160823.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp (+1)
• (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+1-1)

diff --git a/llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp b/llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp
index ee9760f881ae9..143c4c43e611a 100644
--- a/llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp
+++ b/llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp
@@ -905,6 +905,7 @@ bool X86LegalizerInfo::legalizeSETROUNDING(MachineInstr &MI,
     int FieldVal = X86::getRoundingModeX86(RM);
 
     if (FieldVal == X86::rmInvalid) {
+      FieldVal = X86::rmToNearest;
       LLVMContext &C = MF.getFunction().getContext();
       C.diagnose(DiagnosticInfoUnsupported(
           MF.getFunction(), "rounding mode is not supported by X86 hardware",
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 80fbcaa562032..57cf66e5275e3 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -28714,11 +28714,11 @@ SDValue X86TargetLowering::LowerSET_ROUNDING(SDValue Op,
     int FieldVal = X86::getRoundingModeX86(RM);
 
     if (FieldVal == X86::rmInvalid) {
+      FieldVal = X86::rmToNearest;
       LLVMContext &C = MF.getFunction().getContext();
       C.diagnose(DiagnosticInfoUnsupported(
           MF.getFunction(), "rounding mode is not supported by X86 hardware",
           DiagnosticLocation(DL.getDebugLoc()), DS_Error));
-      return {};
     }
     RMBits = DAG.getConstant(FieldVal, DL, MVT::i16);
   } else {

[JaydeepChauhan14]

@RKSimon, @arsenm, @e-kud, @pranavk please review PR.