IVDescriptors: improve readability of a function (NFC)

[artagnon]

Avoid dereferencing operand to llvm::isa.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Ramkumar Ramachandra (artagnon)

Changes

Express a long condtional in terms of an xor, and avoid dereferencing operand to llvm::isa.

---

Full diff: https://github.com/llvm/llvm-project/pull/106219.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/IVDescriptors.cpp (+5-7)

diff --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index ac6df226784345..c4f9785dbc5f66 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -734,13 +734,11 @@ RecurrenceDescriptor::isConditionalRdxPattern(RecurKind Kind, Instruction *I) {
   Value *FalseVal = SI->getFalseValue();
   // Handle only when either of operands of select instruction is a PHI
   // node for now.
-  if ((isa<PHINode>(*TrueVal) && isa<PHINode>(*FalseVal)) ||
-      (!isa<PHINode>(*TrueVal) && !isa<PHINode>(*FalseVal)))
+  if (!(isa<PHINode>(TrueVal) ^ isa<PHINode>(FalseVal)))
     return InstDesc(false, I);
 
-  Instruction *I1 =
-      isa<PHINode>(*TrueVal) ? dyn_cast<Instruction>(FalseVal)
-                             : dyn_cast<Instruction>(TrueVal);
+  Instruction *I1 = isa<PHINode>(TrueVal) ? dyn_cast<Instruction>(FalseVal)
+                                          : dyn_cast<Instruction>(TrueVal);
   if (!I1 || !I1->isBinaryOp())
     return InstDesc(false, I);
 
@@ -754,8 +752,8 @@ RecurrenceDescriptor::isConditionalRdxPattern(RecurKind Kind, Instruction *I) {
         (m_Mul(m_Value(Op1), m_Value(Op2)).match(I1))))
     return InstDesc(false, I);
 
-  Instruction *IPhi = isa<PHINode>(*Op1) ? dyn_cast<Instruction>(Op1)
-                                         : dyn_cast<Instruction>(Op2);
+  Instruction *IPhi = isa<PHINode>(Op1) ? dyn_cast<Instruction>(Op1)
+                                        : dyn_cast<Instruction>(Op2);
   if (!IPhi || IPhi != FalseVal)
     return InstDesc(false, I);
 

[rengolin]

I wouldn't recommend the xor change. Compilers are good at making that change, people are bad at recognising the pattern.

[nikic]

LGTM

[fhahn]

LGTM,thanks!