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[IndVarSimplify] Notify top most loop to drop cached exit counts 

Some nested loops may share the same ExitingBB, so after we finishing FoldExit,
we need to notify OuterLoop and SCEV to drop any stored trip count.

Patched by: guopeilin
Reviewed By: mkazantsev

Differential Revision: https://reviews.llvm.org/D91325
This commit is contained in:
Andrew Wei 2020-11-19 15:34:16 +08:00
parent 7c2990b8af
commit ea7ab5a42c
2 changed files with 67 additions and 1 deletions
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4
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -1790,7 +1790,9 @@ bool IndVarSimplify::run(Loop *L) {
if (optimizeLoopExits(L, Rewriter)) {
Changed = true;
// Given we've changed exit counts, notify SCEV
SE->forgetLoop(L);
// Some nested loops may share same folded exit basic block,
// thus we need to notify top most loop.
SE->forgetTopmostLoop(L);
}
// Try to form loop invariant tests for loop exits by changing how many

64
llvm/test/Transforms/IndVarSimplify/shared-exit-between-nested-loop.ll Normal file
View File

@ -0,0 +1,64 @@
; RUN: opt -indvars -S < %s | FileCheck %s
@__const.e.f = private unnamed_addr constant <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }> <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }> <{ [2 x i32] [i32 4, i32 8], [2 x i32] [i32 3, i32 10], [8 x [2 x i32]] zeroinitializer }>, [10 x [2 x i32]] [[2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] [i32 1, i32 5], [2 x i32] [i32 2080555007, i32 0], [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer, [2 x i32] zeroinitializer] }>, align 4
define dso_local i8 @main() local_unnamed_addr {
entry:
br label %for.cond1.preheader
for.cond1.preheader: ; preds = %for.inc15, %entry
%storemerge32 = phi i32 [ 0, %entry ], [ %inc16, %for.inc15 ]
br label %for.cond4
for.cond4: ; preds = %for.inc, %for.cond1.preheader
%storemerge2531 = phi i32 [ 0, %for.cond1.preheader ], [ %inc, %for.inc ]
%tobool = icmp eq i32 1, 0
br i1 %tobool, label %cleanup, label %if.then
if.then: ; preds = %for.cond4
; CHECK: if.then: ; preds = %for.cond4
; CHECK-NEXT: br i1 false, label %cleanup, label %for.inc
%add = add nuw nsw i32 %storemerge2531, 2
%idxprom8 = zext i32 %add to i64
%arrayidx10 = getelementptr inbounds <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }>, <{ <{ [2 x i32], [2 x i32], [8 x [2 x i32]] }>, [10 x [2 x i32]] }>* @__const.e.f, i64 0, i32 1, i64 %idxprom8, i64 0
%0 = load i32, i32* %arrayidx10, align 4
%tobool11 = icmp eq i32 %0, 0
br i1 %tobool11, label %cleanup, label %for.inc
for.inc: ; preds = %if.then
%inc = add nuw nsw i32 %storemerge2531, 1
%cmp2 = icmp ult i32 %inc, 2
br i1 %cmp2, label %for.cond4, label %for.inc15
cleanup: ; preds = %if.then, %for.cond4
br label %return
for.inc15: ; preds = %for.inc
; CHECK: for.inc15:
; CHECK-NEXT: %inc16 = add nuw nsw i32 %storemerge32, 1
; CHECK-NEXT: %cmp = icmp eq i32 %inc16, 4
; CHECK-NEXT: br i1 %cmp, label %for.cond18thread-pre-split, label %for.cond1.preheader
%inc16 = add nuw nsw i32 %storemerge32, 1
%cmp = icmp eq i32 %inc16, 4
br i1 %cmp, label %for.cond18thread-pre-split, label %for.cond1.preheader
for.cond18thread-pre-split: ; preds = %for.inc15
br i1 1, label %return.loopexit, label %for.inc21.lr.ph
for.inc21.lr.ph: ; preds = %for.cond18thread-pre-split
br label %for.inc21
for.inc21: ; preds = %for.inc21, %for.inc21.lr.ph
%1 = phi i32 [ undef, %for.inc21.lr.ph ], [ %inc22, %for.inc21 ]
%inc22 = add nsw i32 %1, 1
br i1 true, label %for.cond18.return.loopexit_crit_edge, label %for.inc21
for.cond18.return.loopexit_crit_edge: ; preds = %for.inc21
br label %return.loopexit
return.loopexit: ; preds = %for.cond18.return.loopexit_crit_edge, %for.cond18thread-pre-split
br label %return
return: ; preds = %return.loopexit, %cleanup
ret i8 undef
}