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LCSSA: Add a workaround for another nasty SCEV cache invalidation issue.

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I'm not entirely happy with this solution, but I don't see a smarter way currently.
Fixes PR14214.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167112 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2012-10-31 10:01:29 +00:00
parent 0ceb855d52
commit 4ad3d981b9
2 changed files with 79 additions and 0 deletions
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5
lib/Transforms/Utils/LCSSA.cpp
View File

@ -255,6 +255,11 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
if (Loop *L = LI->getLoopFor(ExitBB))
SE->forgetLoop(L);
}
// If we added a PHI, drop the cache to avoid invalidating SCEV caches.
// FIXME: This is a big hammer, can we clear the cache more selectively?
if (SE && !AddedPHIs.empty())
SE->forgetLoop(L);
// Rewrite all uses outside the loop in terms of the new PHIs we just
// inserted.

74
test/Transforms/LoopIdiom/scev-invalidation.ll Normal file
View File

@ -0,0 +1,74 @@
; RUN: opt -S -indvars -loop-idiom < %s
; PR14214
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i32 @quote_arg() nounwind {
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%backslashes.0 = phi i32 [ undef, %entry ], [ %backslashes.2, %for.inc ]
%p.0 = phi i8* [ undef, %entry ], [ %incdec.ptr3, %for.inc ]
%q.0 = phi i8* [ undef, %entry ], [ %q.2, %for.inc ]
%0 = load i8* %p.0, align 1
switch i8 %0, label %while.cond.preheader [
i8 0, label %for.cond4.preheader
i8 92, label %for.inc
]
while.cond.preheader: ; preds = %for.cond
%tobool210 = icmp eq i32 %backslashes.0, 0
br i1 %tobool210, label %for.inc.loopexit, label %while.body.lr.ph
while.body.lr.ph: ; preds = %while.cond.preheader
%1 = add i32 %backslashes.0, -1
%2 = zext i32 %1 to i64
br label %while.body
for.cond4.preheader: ; preds = %for.cond
%tobool57 = icmp eq i32 %backslashes.0, 0
br i1 %tobool57, label %for.end10, label %for.body6.lr.ph
for.body6.lr.ph: ; preds = %for.cond4.preheader
br label %for.body6
while.body: ; preds = %while.body.lr.ph, %while.body
%q.112 = phi i8* [ %q.0, %while.body.lr.ph ], [ %incdec.ptr, %while.body ]
%backslashes.111 = phi i32 [ %backslashes.0, %while.body.lr.ph ], [ %dec, %while.body ]
%incdec.ptr = getelementptr inbounds i8* %q.112, i64 1
store i8 92, i8* %incdec.ptr, align 1
%dec = add nsw i32 %backslashes.111, -1
%tobool2 = icmp eq i32 %dec, 0
br i1 %tobool2, label %while.cond.for.inc.loopexit_crit_edge, label %while.body
while.cond.for.inc.loopexit_crit_edge: ; preds = %while.body
%scevgep.sum = add i64 %2, 1
%scevgep13 = getelementptr i8* %q.0, i64 %scevgep.sum
br label %for.inc.loopexit
for.inc.loopexit: ; preds = %while.cond.for.inc.loopexit_crit_edge, %while.cond.preheader
%q.1.lcssa = phi i8* [ %scevgep13, %while.cond.for.inc.loopexit_crit_edge ], [ %q.0, %while.cond.preheader ]
br label %for.inc
for.inc: ; preds = %for.inc.loopexit, %for.cond
%backslashes.2 = phi i32 [ %backslashes.0, %for.cond ], [ 0, %for.inc.loopexit ]
%q.2 = phi i8* [ %q.0, %for.cond ], [ %q.1.lcssa, %for.inc.loopexit ]
%incdec.ptr3 = getelementptr inbounds i8* %p.0, i64 1
br label %for.cond
for.body6: ; preds = %for.body6.lr.ph, %for.body6
%q.39 = phi i8* [ %q.0, %for.body6.lr.ph ], [ %incdec.ptr7, %for.body6 ]
%backslashes.38 = phi i32 [ %backslashes.0, %for.body6.lr.ph ], [ %dec9, %for.body6 ]
%incdec.ptr7 = getelementptr inbounds i8* %q.39, i64 1
store i8 92, i8* %incdec.ptr7, align 1
%dec9 = add nsw i32 %backslashes.38, -1
%tobool5 = icmp eq i32 %dec9, 0
br i1 %tobool5, label %for.cond4.for.end10_crit_edge, label %for.body6
for.cond4.for.end10_crit_edge: ; preds = %for.body6
br label %for.end10
for.end10: ; preds = %for.cond4.for.end10_crit_edge, %for.cond4.preheader
ret i32 undef
}