[llvm] c2e76f9 - [InstCombine] Use simplifyWithOpReplaced() for non-bool selects

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-09-22T15:46:00+02:00
New Revision: c2e76f914c9ac0dd15e4a8040a5e277333f91f97

URL: https://github.com/llvm/llvm-project/commit/c2e76f914c9ac0dd15e4a8040a5e277333f91f97
DIFF: https://github.com/llvm/llvm-project/commit/c2e76f914c9ac0dd15e4a8040a5e277333f91f97.diff

LOG: [InstCombine] Use simplifyWithOpReplaced() for non-bool selects

Perform the simplifyWithOpReplaced() fold even for non-bool
selects. This subsumes a number of recently added folds for
zext/sext of the condition.

We still need to manually handle variations with both sext/zext
and not, because simplifyWithOpReplaced() only performs one
level of replacements.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index b316be4f9263..58c628abecd6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -2664,46 +2664,40 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
   // If the type of select is not an integer type or if the condition and
   // the selection type are not both scalar nor both vector types, there is no
   // point in attempting to match these patterns.
+  Type *CondType = CondVal->getType();
   if (!isa<Constant>(CondVal) && SelType->isIntOrIntVectorTy() &&
-      CondVal->getType()->isVectorTy() == SelType->isVectorTy()) {
-    auto *One = ConstantInt::get(SelType, 1);
-    auto *Zero = ConstantInt::get(SelType, 0);
-    auto *AllOnes = ConstantInt::get(SelType, -1, /*isSigned*/ true);
-
-    // select a, a, b -> select a, 1, b
-    // select a, zext(a), b -> select a, 1, b
-    if (match(TrueVal, m_ZExtOrSelf(m_Specific(CondVal))))
-      return replaceOperand(SI, 1, One);
-
-    // select a, sext(a), b -> select a, -1, b
-    if (match(TrueVal, m_SExt(m_Specific(CondVal))))
-      return replaceOperand(SI, 1, AllOnes);
+      CondType->isVectorTy() == SelType->isVectorTy()) {
+    if (Value *S = simplifyWithOpReplaced(TrueVal, CondVal,
+                                          ConstantInt::getTrue(CondType), SQ,
+                                          /* AllowRefinement */ true))
+      return replaceOperand(SI, 1, S);
 
-    // select a, b, a -> select a, b, 0
-    // select a, b, zext(a) -> select a, b, 0
-    // select a, b, sext(a) -> select a, b, 0
-    if (match(FalseVal, m_ZExtOrSExtOrSelf(m_Specific(CondVal))))
-      return replaceOperand(SI, 2, Zero);
+    if (Value *S = simplifyWithOpReplaced(FalseVal, CondVal,
+                                          ConstantInt::getFalse(CondType), SQ,
+                                          /* AllowRefinement */ true))
+      return replaceOperand(SI, 2, S);
 
+    // Handle patterns involving sext/zext + not explicitly,
+    // as simplifyWithOpReplaced() only looks past one instruction.
     Value *NotCond;
 
-    // select a, !a, b -> select !a, b, 0
     // select a, sext(!a), b -> select !a, b, 0
     // select a, zext(!a), b -> select !a, b, 0
-    if (match(TrueVal, m_ZExtOrSExtOrSelf(m_CombineAnd(
-                           m_Value(NotCond), m_Not(m_Specific(CondVal))))))
-      return SelectInst::Create(NotCond, FalseVal, Zero);
+    if (match(TrueVal, m_ZExtOrSExt(m_CombineAnd(m_Value(NotCond),
+                                                 m_Not(m_Specific(CondVal))))))
+      return SelectInst::Create(NotCond, FalseVal,
+                                Constant::getNullValue(SelType));
 
-    // select a, b, !a -> select !a, 1, b
     // select a, b, zext(!a) -> select !a, 1, b
-    if (match(FalseVal, m_ZExtOrSelf(m_CombineAnd(m_Value(NotCond),
-                                                  m_Not(m_Specific(CondVal))))))
-      return SelectInst::Create(NotCond, One, TrueVal);
+    if (match(FalseVal, m_ZExt(m_CombineAnd(m_Value(NotCond),
+                                            m_Not(m_Specific(CondVal))))))
+      return SelectInst::Create(NotCond, ConstantInt::get(SelType, 1), TrueVal);
 
     // select a, b, sext(!a) -> select !a, -1, b
     if (match(FalseVal, m_SExt(m_CombineAnd(m_Value(NotCond),
                                             m_Not(m_Specific(CondVal))))))
-      return SelectInst::Create(NotCond, AllOnes, TrueVal);
+      return SelectInst::Create(NotCond, Constant::getAllOnesValue(SelType),
+                                TrueVal);
   }
 
   // Avoid potential infinite loops by checking for non-constant condition.
@@ -2794,13 +2788,6 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
       return BinaryOperator::CreateAnd(FalseVal, Builder.CreateOr(C, TrueVal));
     }
 
-    if (Value *S = simplifyWithOpReplaced(TrueVal, CondVal, One, SQ,
-                                          /* AllowRefinement */ true))
-      return replaceOperand(SI, 1, S);
-    if (Value *S = simplifyWithOpReplaced(FalseVal, CondVal, Zero, SQ,
-                                          /* AllowRefinement */ true))
-      return replaceOperand(SI, 2, S);
-
     if (match(FalseVal, m_Zero()) || match(TrueVal, m_One())) {
       Use *Y = nullptr;
       bool IsAnd = match(FalseVal, m_Zero()) ? true : false;