diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index 0fbf3e08319..59e8e5e5fd1 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -725,12 +725,22 @@ SingleBlockLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) { } case Instruction::Select: { // Widen selects. - // TODO: If the selector is loop invariant we can issue a select - // instruction with a scalar condition. - Value *A = getVectorValue(Inst->getOperand(0)); - Value *B = getVectorValue(Inst->getOperand(1)); - Value *C = getVectorValue(Inst->getOperand(2)); - WidenMap[Inst] = Builder.CreateSelect(A, B, C); + // If the selector is loop invariant we can create a select + // instruction with a scalar condition. Otherwise, use vector-select. + Value *Cond = Inst->getOperand(0); + bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(Cond), Orig); + + // The condition can be loop invariant but still defined inside the + // loop. This means that we can't just use the original 'cond' value. + // We have to take the 'vectorized' value and pick the first lane. + // Instcombine will make this a no-op. + Cond = getVectorValue(Cond); + if (InvariantCond) + Cond = Builder.CreateExtractElement(Cond, Builder.getInt32(0)); + + Value *Op0 = getVectorValue(Inst->getOperand(1)); + Value *Op1 = getVectorValue(Inst->getOperand(2)); + WidenMap[Inst] = Builder.CreateSelect(Cond, Op0, Op1); break; } diff --git a/test/Transforms/LoopVectorize/scalar-select.ll b/test/Transforms/LoopVectorize/scalar-select.ll new file mode 100644 index 00000000000..8d5b6fd8aff --- /dev/null +++ b/test/Transforms/LoopVectorize/scalar-select.ll @@ -0,0 +1,37 @@ +; RUN: opt < %s -loop-vectorize -dce -instcombine -licm -S | FileCheck %s + +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128" +target triple = "x86_64-apple-macosx10.8.0" + +@a = common global [2048 x i32] zeroinitializer, align 16 +@b = common global [2048 x i32] zeroinitializer, align 16 +@c = common global [2048 x i32] zeroinitializer, align 16 + +;CHECK: @example1 +;CHECK: load <4 x i32> +; make sure that we have a scalar condition and a vector operand. +;CHECK: select i1 %cond, <4 x i32> +;CHECK: store <4 x i32> +;CHECK: ret void +define void @example1(i1 %cond) nounwind uwtable ssp { + br label %1 + +;