[InstCombine] Generalize sub of selects optimization to all BinaryOperators
This exposes further optimization opportunities if the selects are
correlated.
llvm-svn: 242235
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index fd34a24..d04ae07 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -623,6 +623,33 @@
}
}
+ // (op (select (a, c, b)), (select (a, d, b))) -> (select (a, (op c, d), 0))
+ // (op (select (a, b, c)), (select (a, b, d))) -> (select (a, 0, (op c, d)))
+ if (auto *SI0 = dyn_cast<SelectInst>(LHS)) {
+ if (auto *SI1 = dyn_cast<SelectInst>(RHS)) {
+ if (SI0->getCondition() == SI1->getCondition()) {
+ Value *SI = nullptr;
+ if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getFalseValue(),
+ SI1->getFalseValue(), DL, TLI, DT, AC))
+ SI = Builder->CreateSelect(SI0->getCondition(),
+ Builder->CreateBinOp(TopLevelOpcode,
+ SI0->getTrueValue(),
+ SI1->getTrueValue()),
+ V);
+ if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getTrueValue(),
+ SI1->getTrueValue(), DL, TLI, DT, AC))
+ SI = Builder->CreateSelect(
+ SI0->getCondition(), V,
+ Builder->CreateBinOp(TopLevelOpcode, SI0->getFalseValue(),
+ SI1->getFalseValue()));
+ if (SI) {
+ SI->takeName(&I);
+ return SI;
+ }
+ }
+ }
+ }
+
return nullptr;
}