maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[LoopPred] Extend LFTR normalization to the inverse EQ case 

A while back, I added support for NE latches formed by LFTR.  I didn't think that quite through, as LFTR will also produce the inverse EQ form for some loops and I hadn't handled that.  This change just adds handling for that case as well.

llvm-svn: 365419
This commit is contained in:
Philip Reames 2019-07-09 01:27:45 +00:00
parent 8f9a4b2af0
commit 5a637cbdc7
2 changed files with 48 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
llvm/lib/Transforms/Scalar/LoopPredication.cpp
View File

@ -653,6 +653,11 @@ static void normalizePredicate(ScalarEvolution *SE, Loop *L,
RC.IV->getStepRecurrence(*SE)->isOne() &&
SE->isKnownPredicate(ICmpInst::ICMP_ULE, RC.IV->getStart(), RC.Limit))
RC.Pred = ICmpInst::ICMP_ULT;
if (RC.Pred == ICmpInst::ICMP_EQ &&
RC.IV->getStepRecurrence(*SE)->isOne() &&
SE->isKnownPredicate(ICmpInst::ICMP_ULE, RC.IV->getStart(), RC.Limit))
RC.Pred = ICmpInst::ICMP_UGE;
}

43
llvm/test/Transforms/LoopPredication/basic.ll
View File

@ -1756,6 +1756,49 @@ exit:
ret i32 0
}
; Same as previous, except swapped br/cmp
define i32 @eq_latch_dom_check_preinc(i32* %array, i32 %length, i32 %n) {
; CHECK-LABEL: @eq_latch_dom_check_preinc(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP5:%.*]] = icmp sle i32 [[N:%.*]], 0
; CHECK-NEXT: br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[LENGTH:%.*]], -1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule i32 [[N]], [[TMP0]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i32 0, [[LENGTH]]
; CHECK-NEXT: [[TMP3:%.*]] = and i1 [[TMP2]], [[TMP1]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 [[TMP3]], i32 9) [ "deopt"() ]
; CHECK-NEXT: [[I_NEXT]] = add nuw i32 [[I]], 1
; CHECK-NEXT: [[DONE:%.*]] = icmp eq i32 [[I]], [[N]]
; CHECK-NEXT: br i1 [[DONE]], label [[EXIT_LOOPEXIT:%.*]], label [[LOOP]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret i32 0
;
entry:
%tmp5 = icmp sle i32 %n, 0
br i1 %tmp5, label %exit, label %loop.preheader
loop.preheader:
br label %loop
loop:
%i = phi i32 [ %i.next, %loop ], [ 0, %loop.preheader ]
%within.bounds = icmp ult i32 %i, %length
call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
%i.next = add nuw i32 %i, 1
%done = icmp eq i32 %i, %n
br i1 %done, label %exit, label %loop
exit:
ret i32 0
}
; NE latch - can't prove (end-start) mod step == 0 (i.e. might wrap
; around several times or even be infinite)