From: David Green Date: Sun, 11 Aug 2019 08:53:18 +0000 (+0000) Subject: [MVE] Don't try to unroll vectorised MVE loops X-Git-Tag: llvmorg-11-init~12179 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=11c4602fce16c22858de764bff21be4160d323af;p=platform%2Fupstream%2Fllvm.git [MVE] Don't try to unroll vectorised MVE loops Due to the nature of the beat system in the MVE architecture, along with tail predication and low-overhead loops, unrolling has less benefit compared to normal loops. You can not, for example, hide the latency of a load with other instructions as you can for scalar code. Preventing unrolling also makes the code easier to read and reason about. So if a loop contains vector code, don't enable the runtime unrolling. At least for the time being. Differential Revision: https://reviews.llvm.org/D65803 llvm-svn: 368530 --- diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp index fb5b08d..9f5f40c 100644 --- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp +++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp @@ -893,6 +893,11 @@ void ARMTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE, } return; } + // Don't unroll vectorised loop. MVE does not benefit from it as much as + // scalar code. + if (I.getType()->isVectorTy()) + return; + SmallVector Operands(I.value_op_begin(), I.value_op_end()); Cost += getUserCost(&I, Operands); diff --git a/llvm/test/Transforms/LoopUnroll/ARM/mve-nounroll.ll b/llvm/test/Transforms/LoopUnroll/ARM/mve-nounroll.ll new file mode 100644 index 0000000..2067969a --- /dev/null +++ b/llvm/test/Transforms/LoopUnroll/ARM/mve-nounroll.ll @@ -0,0 +1,127 @@ +; RUN: opt -mtriple=thumbv8.1m.main -mattr=+mve.fp -loop-unroll -S < %s -o - | FileCheck %s + +; CHECK-LABEL: @loopfn +; CHECK: vector.body: +; CHECK: br i1 %7, label %middle.block, label %vector.body, !llvm.loop !0 +; CHECK: middle.block: +; CHECK: br i1 %cmp.n, label %for.cond.cleanup, label %for.body.preheader13 +; CHECK: for.body: +; CHECK: br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body, !llvm.loop !2 + +define void @loopfn(float* %s1, float* %s2, float* %d, i32 %n) { +entry: + %cmp10 = icmp sgt i32 %n, 0 + br i1 %cmp10, label %for.body.preheader, label %for.cond.cleanup + +for.body.preheader: ; preds = %entry + %min.iters.check = icmp ult i32 %n, 4 + br i1 %min.iters.check, label %for.body.preheader13, label %vector.ph + +for.body.preheader13: ; preds = %middle.block, %for.body.preheader + %i.011.ph = phi i32 [ 0, %for.body.preheader ], [ %n.vec, %middle.block ] + br label %for.body + +vector.ph: ; preds = %for.body.preheader + %n.vec = and i32 %n, -4 + br label %vector.body + +vector.body: ; preds = %vector.body, %vector.ph + %index = phi i32 [ 0, %vector.ph ], [ %index.next, %vector.body ] + %0 = getelementptr inbounds float, float* %s1, i32 %index + %1 = bitcast float* %0 to <4 x float>* + %wide.load = load <4 x float>, <4 x float>* %1, align 4 + %2 = getelementptr inbounds float, float* %s2, i32 %index + %3 = bitcast float* %2 to <4 x float>* + %wide.load12 = load <4 x float>, <4 x float>* %3, align 4 + %4 = fadd fast <4 x float> %wide.load12, %wide.load + %5 = getelementptr inbounds float, float* %d, i32 %index + %6 = bitcast float* %5 to <4 x float>* + store <4 x float> %4, <4 x float>* %6, align 4 + %index.next = add i32 %index, 4 + %7 = icmp eq i32 %index.next, %n.vec + br i1 %7, label %middle.block, label %vector.body, !llvm.loop !0 + +middle.block: ; preds = %vector.body + %cmp.n = icmp eq i32 %n.vec, %n + br i1 %cmp.n, label %for.cond.cleanup, label %for.body.preheader13 + +for.cond.cleanup.loopexit: ; preds = %for.body + br label %for.cond.cleanup + +for.cond.cleanup: ; preds = %for.cond.cleanup.loopexit, %middle.block, %entry + ret void + +for.body: ; preds = %for.body.preheader13, %for.body + %i.011 = phi i32 [ %add3, %for.body ], [ %i.011.ph, %for.body.preheader13 ] + %arrayidx = getelementptr inbounds float, float* %s1, i32 %i.011 + %8 = load float, float* %arrayidx, align 4 + %arrayidx1 = getelementptr inbounds float, float* %s2, i32 %i.011 + %9 = load float, float* %arrayidx1, align 4 + %add = fadd fast float %9, %8 + %arrayidx2 = getelementptr inbounds float, float* %d, i32 %i.011 + store float %add, float* %arrayidx2, align 4 + %add3 = add nuw nsw i32 %i.011, 1 + %exitcond = icmp eq i32 %add3, %n + br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body, !llvm.loop !2 +} + + + +; CHECK-LABEL: @nested +; CHECK: for.outer: +; CHECK: br label %vector.body +; CHECK: vector.body: +; CHECK: br i1 %8, label %for.latch, label %vector.body, !llvm.loop !0 +; CHECK: for.latch: +; CHECK: br i1 %exitcond34, label %for.cond.cleanup.loopexit, label %for.outer + +define void @nested(float* %s1, float* %s2, float* %d, i32 %n) { +entry: + %cmp31 = icmp eq i32 %n, 0 + br i1 %cmp31, label %for.cond.cleanup, label %for.outer.preheader + +for.outer.preheader: ; preds = %entry + %min.iters.check = icmp ult i32 %n, 4 + %n.vec = and i32 %n, -4 + %cmp.n = icmp eq i32 %n.vec, %n + br label %for.outer + +for.outer: ; preds = %for.outer.preheader, %for.cond1.for.cond.cleanup3_crit_edge.us + %j.032.us = phi i32 [ %inc.us, %for.latch ], [ 0, %for.outer.preheader ] + %mul.us = mul i32 %j.032.us, %n + br label %vector.body + +vector.body: ; preds = %for.outer, %vector.body + %index = phi i32 [ %index.next, %vector.body ], [ 0, %for.outer ] + %0 = add i32 %index, %mul.us + %1 = getelementptr inbounds float, float* %s1, i32 %0 + %2 = bitcast float* %1 to <4 x float>* + %wide.load = load <4 x float>, <4 x float>* %2, align 4 + %3 = getelementptr inbounds float, float* %s2, i32 %0 + %4 = bitcast float* %3 to <4 x float>* + %wide.load35 = load <4 x float>, <4 x float>* %4, align 4 + %5 = fadd fast <4 x float> %wide.load35, %wide.load + %6 = getelementptr inbounds float, float* %d, i32 %0 + %7 = bitcast float* %6 to <4 x float>* + store <4 x float> %5, <4 x float>* %7, align 4 + %index.next = add i32 %index, 4 + %8 = icmp eq i32 %index.next, %n.vec + br i1 %8, label %for.latch, label %vector.body, !llvm.loop !0 + +for.latch: ; preds = %vector.body, %for.outer + %i.030.us.ph = phi i32 [ %n.vec, %vector.body ] + %inc.us = add nuw i32 %j.032.us, 1 + %exitcond34 = icmp eq i32 %inc.us, %n + br i1 %exitcond34, label %for.cond.cleanup.loopexit, label %for.outer + +for.cond.cleanup.loopexit: + br label %for.cond.cleanup + +for.cond.cleanup: ; preds = %for.cond1.for.cond.cleanup3_crit_edge.us, %entry + ret void +} + +!0 = distinct !{!0, !1} +!1 = !{!"llvm.loop.isvectorized", i32 1} +!2 = distinct !{!2, !3, !1} +!3 = !{!"llvm.loop.unroll.runtime.disable"}