[InstSimplify] Fold more Select with Or pattern

[liaolucy]

Summary

Issue: #59196
https://alive2.llvm.org/ce/z/Li-Eqq

[spatel]

This looks right, but it is incomplete - it does not handle the commuted pattern?
D138700 says it handles this and more, so let's proceed with that patch.
@bcl5980 - a vector test as shown here would be a good addition.

[liaolucy]

Let's proceed with D138700. I abandon this patch

llvm/lib/Analysis/InstructionSimplify.cpp

 static Value *foldSelectWithBinaryOp(Value *Cond, Value *TrueVal,
                                      Value *FalseVal) {
   BinaryOperator::BinaryOps BinOpCode;
   if (auto *BO = dyn_cast<BinaryOperator>(Cond))
     BinOpCode = BO->getOpcode();
   else
     return nullptr;
 
+  // %C = or %FV, %TV
+  // %D = select %C, %TV, %FV
+  // -->
+  // %TV
+  if (BinOpCode == BinaryOperator::Or &&
+      match(Cond, m_LogicalOr(m_Specific(FalseVal), m_Specific(TrueVal))))
+    return TrueVal;
+
   CmpInst::Predicate ExpectedPred, Pred1, Pred2;
   if (BinOpCode == BinaryOperator::Or) {
     ExpectedPred = ICmpInst::ICMP_NE;
   } else if (BinOpCode == BinaryOperator::And) {
     ExpectedPred = ICmpInst::ICMP_EQ;
   } else
     return nullptr;
 

llvm/test/Transforms/InstSimplify/select-or-cmp.ll

 ; CHECK-NEXT:    ret i32 [[D]]
 ;
   %A = icmp ne i32 %x, %z
   %B = icmp ne i32 %y, %z
   %C = or i1 %A, %B
   %D = select i1 %C, i32 %x, i32 %k
   ret i32 %D
 }
+
+define i1 @select_or_return_true(i1 %x, i1 %y) {
+; CHECK-LABEL: @select_or_return_true(
+; CHECK-NEXT:    ret i1 [[Y:%.*]]
+;
+  %C = or i1 %x, %y
+  %D = select i1 %C, i1 %y, i1 %x
+  ret i1 %D
+}
+
+define <2 x i1> @select_or_return_true1(<2 x i1> %x, <2 x i1> %y) {
+; CHECK-LABEL: @select_or_return_true1(
+; CHECK-NEXT:    ret <2 x i1> [[Y:%.*]]
+;
+  %C = or <2 x i1> %x, %y
+  %D = select <2 x i1>  %C, <2 x i1>  %y, <2 x i1> %x
+  ret <2 x i1> %D
+}