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[ARM] Enable Unroll UpperBound 

This option allows loops with small max trip counts to be fully unrolled. This
can help with code like the remainder loops from manually unrolled loops like
those that appear in the cmsis dsp library. We would apparently previously
runtime unroll them with the default unroll count (4).

Differential Revision: https://reviews.llvm.org/D63064

llvm-svn: 362928
This commit is contained in:
David Green 2019-06-10 10:22:14 +00:00
parent c6a930e4b4
commit d847aa573b
2 changed files with 39 additions and 0 deletions
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1
llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
View File

@ -683,6 +683,7 @@ void ARMTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
UP.Partial = true; UP.Partial = true;
UP.Runtime = true; UP.Runtime = true;
UP.UpperBound = true;
UP.UnrollRemainder = true; UP.UnrollRemainder = true;
UP.DefaultUnrollRuntimeCount = 4; UP.DefaultUnrollRuntimeCount = 4;
UP.UnrollAndJam = true; UP.UnrollAndJam = true;

38
llvm/test/Transforms/LoopUnroll/ARM/upperbound.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: opt -loop-unroll -S -mtriple arm-none-eabi -mcpu=cortex-m7 %s | FileCheck %s -check-prefix=UNROLL
; This test is meant to check that this loop is unrolled into three iterations.
; UNROLL-LABEL: @test
; UNROLL: load i32, i32*
; UNROLL: load i32, i32*
; UNROLL: load i32, i32*
; UNROLL-NOT: load i32, i32*
define void @test(i32* %x, i32 %n) {
entry:
%sub = add nsw i32 %n, -1
%rem = srem i32 %sub, 4
%cmp7 = icmp sgt i32 %rem, 0
br i1 %cmp7, label %while.body, label %while.end
while.body: ; preds = %entry, %if.end
%x.addr.09 = phi i32* [ %incdec.ptr, %if.end ], [ %x, %entry ]
%n.addr.08 = phi i32 [ %dec, %if.end ], [ %rem, %entry ]
%0 = load i32, i32* %x.addr.09, align 4
%cmp1 = icmp slt i32 %0, 10
br i1 %cmp1, label %if.then, label %if.end
if.then: ; preds = %while.body
store i32 0, i32* %x.addr.09, align 4
br label %if.end
if.end: ; preds = %if.then, %while.body
%incdec.ptr = getelementptr inbounds i32, i32* %x.addr.09, i32 1
%dec = add nsw i32 %n.addr.08, -1
%cmp = icmp sgt i32 %dec, 0
br i1 %cmp, label %while.body, label %while.end
while.end: ; preds = %if.end, %entry
ret void
}