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Revert "Fix PR18361: Invalidate LoopDispositions after LoopSimplify hoists things."

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This commit was the source of crasher PR18384:

While deleting: label %for.cond127
An asserting value handle still pointed to this value!
UNREACHABLE executed at llvm/lib/IR/Value.cpp:671!

Reverting to get the builders green, feel free to re-land after fixing up.
(Renato has a handy isolated repro if you need it.)

This reverts commit r198478.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198503 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Alp Toker 2014-01-04 17:00:45 +00:00
parent 72d2b05254
commit ccd36c4c54
3 changed files with 10 additions and 104 deletions
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7
include/llvm/Analysis/ScalarEvolution.h
View File

@ -784,13 +784,6 @@ namespace llvm {
/// disconnect it from a def-use chain linking it to a loop.
void forgetValue(Value *V);
/// \brief Called when the client has changed the disposition of values in
/// this loop.
///
/// We don't have a way to invalidate per-loop dispositions. Clear and
/// recompute is simpler.
void forgetLoopDispositions(const Loop *L) { LoopDispositions.clear(); }
/// GetMinTrailingZeros - Determine the minimum number of zero bits that S
/// is guaranteed to end in (at every loop iteration). It is, at the same
/// time, the minimum number of times S is divisible by 2. For example,

27
lib/Transforms/Utils/LoopSimplify.cpp
View File

@ -309,7 +309,6 @@ ReprocessLoop:
// Attempt to hoist out all instructions except for the
// comparison and the branch.
bool AllInvariant = true;
bool AnyInvariant = false;
for (BasicBlock::iterator I = ExitingBlock->begin(); &*I != BI; ) {
Instruction *Inst = I++;
// Skip debug info intrinsics.
@ -317,26 +316,12 @@ ReprocessLoop:
continue;
if (Inst == CI)
continue;
if (!L->makeLoopInvariant(Inst, AnyInvariant,
Preheader ? Preheader->getTerminator() : 0)) {
if (!L->makeLoopInvariant(Inst, Changed,
Preheader ? Preheader->getTerminator() : 0)) {
AllInvariant = false;
break;
}
}
if (AnyInvariant) {
Changed = true;
// If any reachable control flow within this loop has changed, notify
// ScalarEvolution. Currently assume the parent loop doesn't change
// (spliting edges doesn't count). If blocks, CFG edges, or other values
// in the parent loop change, then we need call to forgetLoop() for the
// parent instead.
if (SE) {
SE->forgetLoop(L);
// The loop disposition of all SCEV expressions that depend on any
// hoisted values have also changed.
SE->forgetLoopDispositions(L);
}
}
if (!AllInvariant) continue;
// The block has now been cleared of all instructions except for
@ -349,6 +334,14 @@ ReprocessLoop:
DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
<< ExitingBlock->getName() << "\n");
// If any reachable control flow within this loop has changed, notify
// ScalarEvolution. Currently assume the parent loop doesn't change
// (spliting edges doesn't count). If blocks, CFG edges, or other values
// in the parent loop change, then we need call to forgetLoop() for the
// parent instead.
if (SE)
SE->forgetLoop(L);
assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
Changed = true;
LI->removeBlock(ExitingBlock);

80
test/Transforms/LoopSimplify/ashr-crash.ll
View File

@ -1,80 +0,0 @@
; RUN: opt -basicaa -loop-rotate -licm -instcombine -indvars -loop-unroll -S %s | FileCheck %s
;
; PR18361: ScalarEvolution::getAddRecExpr():
; Assertion `isLoopInvariant(Operands[i],...
;
; After a series of loop optimizations, SCEV's LoopDispositions grow stale.
; In particular, LoopSimplify hoists %cmp4, resulting in this SCEV for %add:
; {(zext i1 %cmp4 to i32),+,1}<nw><%for.cond1.preheader>
;
; When recomputing the SCEV for %ashr, we truncate the operands to get:
; (zext i1 %cmp4 to i16)
;
; This SCEV was never mapped to a value so never invalidated. It's
; loop disposition is still marked as non-loop-invariant, which is
; inconsistent with the AddRec.
target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx"
@d = common global i32 0, align 4
@a = common global i32 0, align 4
@c = common global i32 0, align 4
@b = common global i32 0, align 4
; Check that the def-use chain that leads to the bad SCEV is still
; there, and part of it is hoisted to the entry block.
;
; CHECK-LABEL: @foo
; CHECK-LABEL: entry:
; CHECK: %cmp4
; CHECK-LABEL: for.cond1.preheader:
; CHECK-LABEL: for.body3:
; CHECK: %1 = zext i1 %cmp4 to i32
; CHECK: %xor = xor i32 %1, 1
define void @foo() {
entry:
br label %for.cond
for.cond: ; preds = %for.inc7, %entry
%storemerge = phi i32 [ 0, %entry ], [ %inc8, %for.inc7 ]
%f.0 = phi i32 [ undef, %entry ], [ %f.1, %for.inc7 ]
store i32 %storemerge, i32* @d, align 4
%cmp = icmp slt i32 %storemerge, 1
br i1 %cmp, label %for.cond1, label %for.end9
for.cond1: ; preds = %for.cond, %for.body3
%storemerge1 = phi i32 [ %inc, %for.body3 ], [ 0, %for.cond ]
%f.1 = phi i32 [ %xor, %for.body3 ], [ %f.0, %for.cond ]
store i32 %storemerge1, i32* @a, align 4
%cmp2 = icmp slt i32 %storemerge1, 1
br i1 %cmp2, label %for.body3, label %for.inc7
for.body3: ; preds = %for.cond1
%0 = load i32* @c, align 4
%cmp4 = icmp sge i32 %storemerge1, %0
%conv = zext i1 %cmp4 to i32
%1 = load i32* @d, align 4
%add = add nsw i32 %conv, %1
%sext = shl i32 %add, 16
%conv6 = ashr exact i32 %sext, 16
%xor = xor i32 %conv6, 1
%inc = add nsw i32 %storemerge1, 1
br label %for.cond1
for.inc7: ; preds = %for.cond1
%2 = load i32* @d, align 4
%inc8 = add nsw i32 %2, 1
br label %for.cond
for.end9: ; preds = %for.cond
%cmp10 = icmp sgt i32 %f.0, 0
br i1 %cmp10, label %if.then, label %if.end
if.then: ; preds = %for.end9
store i32 0, i32* @b, align 4
br label %if.end
if.end: ; preds = %if.then, %for.end9
ret void
}