[InstCombine] Fold Select with AND/OR condition
Summary:
Fold
```
%A = icmp ne i8 %X, %V1
%B = icmp ne i8 %X, %V2
%C = or i1 %A, %B
%D = select i1 %C, i8 %X, i8 %V1
ret i8 %D
=>
ret i8 %X
Fixes https://bugs.llvm.org/show_bug.cgi?id=38334
Proof: https://rise4fun.com/Alive/plI8
Reviewers: spatel, lebedev.ri
Reviewed By: lebedev.ri
Subscribers: craig.topper, llvm-commits
Differential Revision: https://reviews.llvm.org/D49919
llvm-svn: 338191
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 519d6d6..257fa70 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -65,6 +65,40 @@
static Value *SimplifyGEPInst(Type *, ArrayRef<Value *>, const SimplifyQuery &,
unsigned);
+/// Fold
+/// %A = icmp ne/eq i8 %X, %V1
+/// %B = icmp ne/eq i8 %X, %V2
+/// %C = or/and i1 %A, %B
+/// %D = select i1 %C, i8 %X, i8 %V1
+/// To
+/// %X/%V1
+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;
+
+ CmpInst::Predicate ExpectedPred;
+ if (BinOpCode == BinaryOperator::Or) {
+ ExpectedPred = ICmpInst::ICMP_NE;
+ } else if (BinOpCode == BinaryOperator::And) {
+ ExpectedPred = ICmpInst::ICMP_EQ;
+ } else
+ return nullptr;
+
+ CmpInst::Predicate Pred1, Pred2;
+ if (!match(
+ Cond,
+ m_c_BinOp(m_c_ICmp(Pred1, m_Specific(TrueVal), m_Specific(FalseVal)),
+ m_c_ICmp(Pred2, m_Specific(TrueVal), m_Value()))) ||
+ Pred1 != Pred2 || Pred1 != ExpectedPred)
+ return nullptr;
+
+ return BinOpCode == BinaryOperator::Or ? TrueVal : FalseVal;
+}
+
/// For a boolean type or a vector of boolean type, return false or a vector
/// with every element false.
static Constant *getFalse(Type *Ty) {
@@ -3752,6 +3786,9 @@
simplifySelectWithICmpCond(Cond, TrueVal, FalseVal, Q, MaxRecurse))
return V;
+ if (Value *V = foldSelectWithBinaryOp(Cond, TrueVal, FalseVal))
+ return V;
+
return nullptr;
}