================
@@ -460,6 +460,70 @@ class OpLowerer {
});
}
+ [[nodiscard]] bool lowerCtpopToCountBits(Function &F) {
+ IRBuilder<> &IRB = OpBuilder.getIRB();
+ Type *Int32Ty = IRB.getInt32Ty();
+
+ return replaceFunction(F, [&](CallInst *CI) -> Error {
+ IRB.SetInsertPoint(CI);
+ SmallVector<Value *> Args;
+ Args.append(CI->arg_begin(), CI->arg_end());
+
+ Type *RetTy = Int32Ty;
+ Type *FRT = F.getReturnType();
+ if (const auto *VT = dyn_cast<VectorType>(FRT))
+ RetTy = VectorType::get(RetTy, VT);
+
+ Expected<CallInst *> OpCall = OpBuilder.tryCreateOp(
+ dxil::OpCode::CountBits, Args, CI->getName(), RetTy);
+ if (Error E = OpCall.takeError())
+ return E;
+
+ // If the result type is 32 bits we can do a direct replacement.
+ if (FRT->isIntOrIntVectorTy(32)) {
+ CI->replaceAllUsesWith(*OpCall);
+ CI->eraseFromParent();
+ return Error::success();
+ }
+
+ unsigned CastOp;
+ if (FRT->isIntOrIntVectorTy(16))
+ CastOp = Instruction::ZExt;
+ else { // must be 64 bits
+ assert(FRT->isIntOrIntVectorTy(64) &&
+ "Currently only lowering 16, 32, or 64 bit ctpop to CountBits \
+ is supported.");
+ CastOp = Instruction::Trunc;
+ }
+
+ // It is correct to replace the ctpop with the dxil op and
+ // remove all casts to i32
+ bool nonCastInstr = false;
+ for (User *User : make_early_inc_range(CI->users())) {
+ Instruction *I;
+ if ((I = dyn_cast<Instruction>(User)) != NULL &&
+ I->getOpcode() == CastOp && I->getType() == RetTy) {
----------------
bogner wrote:
Burying the assignment in the condition makes this a bit less readable.
Probably best to initialize `I` before the condition. Also, it's better to use
`nullptr_t` or just use the implicit conversion to bool rather than compare to
`NULL`.
```suggestion
Instruction *I = dyn_cast<Instruction>(User)
if (I && I->getOpcode() == CastOp && I->getType() == RetTy) {
```
https://github.com/llvm/llvm-project/pull/113189
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