================
@@ -184,6 +185,53 @@ static mlir::Value emitX86Select(CIRGenBuilderTy &builder,
mlir::Location loc,
return cir::VecTernaryOp::create(builder, loc, mask, op0, op1);
}
+static mlir::Value emitX86ScalarSelect(CIRGenBuilderTy &builder,
+ mlir::Location loc, mlir::Value mask,
+ mlir::Value op0, mlir::Value op1) {
+
+ // If the mask is all ones just return first argument.
+ if (auto c = mlir::dyn_cast_or_null<cir::ConstantOp>(mask.getDefiningOp()))
+ if (c.isAllOnesValue())
+ return op0;
+
+ // Extract the scalar values from the vector operands
+ auto vecTy0 = mlir::dyn_cast<cir::VectorType>(op0.getType());
+ auto vecTy1 = mlir::dyn_cast<cir::VectorType>(op1.getType());
+
+ mlir::Value scalar0 = op0;
+ mlir::Value scalar1 = op1;
+
+ if (vecTy0)
+ scalar0 = builder.createExtractElement(loc, op0, uint64_t(0));
+
+ if (vecTy1)
+ scalar1 = builder.createExtractElement(loc, op1, uint64_t(0));
+
+ // Get the mask as a vector of i1 and extract bit 0
+ auto intTy = mlir::dyn_cast<cir::IntType>(mask.getType());
+ assert(intTy && "mask must be an integer type");
+ unsigned width = intTy.getWidth();
+
+ auto i1Ty = builder.getUIntNTy(1);
+ auto maskVecTy = cir::VectorType::get(i1Ty, width);
+ mlir::Value maskVec = builder.createBitcast(mask, maskVecTy);
+
+ // Extract bit 0 from the mask vector
+ mlir::Value bit0 = builder.createExtractElement(loc, maskVec, uint64_t(0));
----------------
andykaylor wrote:
Can you bundle all of this logic to extract the zero-bit of the mask as a
boolean into a separate helper function? It seems like a good candidate for
future simplification. The optimizer is going to reduce this to `trunc i8 %mask
to i1`. We don't currently have an integer `trunc` operation, and we probably
want to keep the nature of what we're doing here visible in CIR, but all of
this casting and extraction feels quite verbose.
https://github.com/llvm/llvm-project/pull/174003
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