mirror of
https://github.com/RPCS3/llvm.git
synced 2026-07-18 13:16:24 -04:00
[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 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368530 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Green
@@ -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<const Value*, 4> Operands(I.value_op_begin(),
|
||||
I.value_op_end());
|
||||
Cost += getUserCost(&I, Operands);
|
||||
|
||||
@@ -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"}
|
||||
Reference in New Issue
Block a user