PPC: Custom lower ppcf128 is_fpclass if is_fpclass is custom

[arsenm]

Unfortunately expandIS_FPCLASS is called directly in SelectionDAGBuilder
depending on whether IS_FPCLASS is custom or not. This helps avoid ppc test
regressions in a future patch where the custom lowering would be bypassed.

[arsenm]

• DAG: Lower fcNormal is.fpclass to compare with inf #100389
• DAG: Lower single infinity is.fpclass tests to fcmp #100380
• DAG: Handle lowering unordered compare with inf #100378
• DAG: Check if is_fpclass is custom, instead of isLegalOrCustom #105577
• PPC: Custom lower ppcf128 is_fpclass if is_fpclass is custom #105540 👈
• main

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[llvmbot]

@llvm/pr-subscribers-backend-powerpc

Author: Matt Arsenault (arsenm)

Changes

Unfortunately expandIS_FPCLASS is called directly in SelectionDAGBuilder
depending on whether IS_FPCLASS is custom or not. This helps avoid ppc test
regressions in a future patch where the custom lowering would be bypassed.

---

Full diff: https://github.com/llvm/llvm-project/pull/105540.diff

1 Files Affected:

• (modified) llvm/lib/Target/PowerPC/PPCISelLowering.cpp (+7)

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 459a96eca1ff20..a5bc24b55660a5 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -1221,6 +1221,7 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
         setOperationAction(ISD::IS_FPCLASS, MVT::f32, Custom);
         setOperationAction(ISD::IS_FPCLASS, MVT::f64, Custom);
         setOperationAction(ISD::IS_FPCLASS, MVT::f128, Custom);
+        setOperationAction(ISD::IS_FPCLASS, MVT::ppcf128, Custom);
       }
 
       // 128 bit shifts can be accomplished via 3 instructions for SHL and
@@ -11479,6 +11480,12 @@ SDValue PPCTargetLowering::LowerIS_FPCLASS(SDValue Op,
   uint64_t RHSC = Op.getConstantOperandVal(1);
   SDLoc Dl(Op);
   FPClassTest Category = static_cast<FPClassTest>(RHSC);
+  if (LHS.getValueType() == MVT::ppcf128) {
+    // The higher part determines the value class.
+    LHS = DAG.getNode(ISD::EXTRACT_ELEMENT, Dl, MVT::f64, LHS,
+                      DAG.getConstant(1, Dl, MVT::i32));
+  }
+
   return getDataClassTest(LHS, Category, Dl, DAG, Subtarget);
 }
 

[spavloff]

Is this code:

llvm-project/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Lines 8678 to 8684 in 902b2a2

	// PPC double double is a pair of doubles, of which the higher part determines
	// the value class.
	if (OperandVT == MVT::ppcf128) {
	Op = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::f64, Op,
	DAG.getConstant(1, DL, MVT::i32));
	OperandVT = MVT::f64;
	}

is not needed anymore?

[arsenm]

It is still needed. PPC only custom lowers this for Subtarget.useCRBits, otherwise it still hits the default expansion

[spavloff]

LGTM.

[arsenm]

Merge activity

• Aug 29, 5:54 AM EDT: @arsenm started a stack merge that includes this pull request via Graphite.
• Aug 29, 5:56 AM EDT: Graphite rebased this pull request as part of a merge.
• Aug 29, 5:59 AM EDT: Graphite rebased this pull request as part of a merge.
• Aug 29, 6:01 AM EDT: @arsenm merged this pull request with Graphite.