[InstSimplify] Only handle canonical forms in simplifyAndOrOfFCmps. NFC. (#98136)

This patch avoids calling `isKnownNeverNaN` in `simplifyAndOrOfFCmps`
since `fcmp ord/uno X, NNAN` will be canonicalized into `fcmp ord/uno X,
0.0` in InstCombine.

Author: dtcxzyw

llvm/lib/Analysis/InstructionSimplify.cpp

@@ -1872,14 +1872,11 @@ static Value *simplifyAndOrOfFCmps(const SimplifyQuery &Q, FCmpInst *LHS,
   if ((PredL == FCmpInst::FCMP_ORD || PredL == FCmpInst::FCMP_UNO) &&
       ((FCmpInst::isOrdered(PredR) && IsAnd) ||
        (FCmpInst::isUnordered(PredR) && !IsAnd))) {
-    // (fcmp ord X, NNAN) & (fcmp o** X, Y) --> fcmp o** X, Y
-    // (fcmp uno X, NNAN) & (fcmp o** X, Y) --> false
-    // (fcmp uno X, NNAN) | (fcmp u** X, Y) --> fcmp u** X, Y
-    // (fcmp ord X, NNAN) | (fcmp u** X, Y) --> true
-    if (((LHS1 == RHS0 || LHS1 == RHS1) &&
-         isKnownNeverNaN(LHS0, /*Depth=*/0, Q)) ||
-        ((LHS0 == RHS0 || LHS0 == RHS1) &&
-         isKnownNeverNaN(LHS1, /*Depth=*/0, Q)))
+    // (fcmp ord X, 0) & (fcmp o** X, Y) --> fcmp o** X, Y
+    // (fcmp uno X, 0) & (fcmp o** X, Y) --> false
+    // (fcmp uno X, 0) | (fcmp u** X, Y) --> fcmp u** X, Y
+    // (fcmp ord X, 0) | (fcmp u** X, Y) --> true
+    if ((LHS0 == RHS0 || LHS0 == RHS1) && match(LHS1, m_PosZeroFP()))
       return FCmpInst::isOrdered(PredL) == FCmpInst::isOrdered(PredR)
                  ? static_cast<Value *>(RHS)
                  : ConstantInt::getBool(LHS->getType(), !IsAnd);
@@ -1888,14 +1885,11 @@ static Value *simplifyAndOrOfFCmps(const SimplifyQuery &Q, FCmpInst *LHS,
   if ((PredR == FCmpInst::FCMP_ORD || PredR == FCmpInst::FCMP_UNO) &&
       ((FCmpInst::isOrdered(PredL) && IsAnd) ||
        (FCmpInst::isUnordered(PredL) && !IsAnd))) {
-    // (fcmp o** X, Y) & (fcmp ord X, NNAN) --> fcmp o** X, Y
-    // (fcmp o** X, Y) & (fcmp uno X, NNAN) --> false
-    // (fcmp u** X, Y) | (fcmp uno X, NNAN) --> fcmp u** X, Y
-    // (fcmp u** X, Y) | (fcmp ord X, NNAN) --> true
-    if (((RHS1 == LHS0 || RHS1 == LHS1) &&
-         isKnownNeverNaN(RHS0, /*Depth=*/0, Q)) ||
-        ((RHS0 == LHS0 || RHS0 == LHS1) &&
-         isKnownNeverNaN(RHS1, /*Depth=*/0, Q)))
+    // (fcmp o** X, Y) & (fcmp ord X, 0) --> fcmp o** X, Y
+    // (fcmp o** X, Y) & (fcmp uno X, 0) --> false
+    // (fcmp u** X, Y) | (fcmp uno X, 0) --> fcmp u** X, Y
+    // (fcmp u** X, Y) | (fcmp ord X, 0) --> true
+    if ((RHS0 == LHS0 || RHS0 == LHS1) && match(RHS1, m_PosZeroFP()))
       return FCmpInst::isOrdered(PredL) == FCmpInst::isOrdered(PredR)
                  ? static_cast<Value *>(LHS)
                  : ConstantInt::getBool(LHS->getType(), !IsAnd);

llvm/test/Transforms/InstSimplify/logic-of-fcmps.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
 ; Cycle through commuted variants where one operand of fcmp ord/uno is
 ; known not-a-NAN and the other is repeated in the logically-connected fcmp.