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[IRCE] Fix a regression introduced in r232444.

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IRCE should not try to eliminate range checks that check an induction
variable against a loop-varying length.

llvm-svn: 233101
This commit is contained in:
Sanjoy Das 2015-03-24 19:29:18 +00:00
parent b1b1054a09
commit 867451d1ec
2 changed files with 51 additions and 9 deletions
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29
lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
View File

@ -122,8 +122,9 @@ class InductiveRangeCheck {
BranchInst *Branch;
RangeCheckKind Kind;
static RangeCheckKind parseRangeCheckICmp(ICmpInst *ICI, ScalarEvolution &SE,
Value *&Index, Value *&Length);
static RangeCheckKind parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
ScalarEvolution &SE, Value *&Index,
Value *&Length);
static InductiveRangeCheck::RangeCheckKind
parseRangeCheck(Loop *L, ScalarEvolution &SE, Value *Condition,
@ -255,8 +256,18 @@ const char *InductiveRangeCheck::rangeCheckKindToStr(
/// RANGE_CHECK_UPPER.
///
InductiveRangeCheck::RangeCheckKind
InductiveRangeCheck::parseRangeCheckICmp(ICmpInst *ICI, ScalarEvolution &SE,
Value *&Index, Value *&Length) {
InductiveRangeCheck::parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
ScalarEvolution &SE, Value *&Index,
Value *&Length) {
auto IsNonNegativeAndNotLoopVarying = [&SE, L](Value *V) {
const SCEV *S = SE.getSCEV(V);
if (isa<SCEVCouldNotCompute>(S))
return false;
return SE.getLoopDisposition(S, L) == ScalarEvolution::LoopInvariant &&
SE.isKnownNonNegative(S);
};
using namespace llvm::PatternMatch;
@ -287,7 +298,7 @@ InductiveRangeCheck::parseRangeCheckICmp(ICmpInst *ICI, ScalarEvolution &SE,
return RANGE_CHECK_LOWER;
}
if (SE.isKnownNonNegative(SE.getSCEV(LHS))) {
if (IsNonNegativeAndNotLoopVarying(LHS)) {
Index = RHS;
Length = LHS;
return RANGE_CHECK_UPPER;
@ -298,7 +309,7 @@ InductiveRangeCheck::parseRangeCheckICmp(ICmpInst *ICI, ScalarEvolution &SE,
std::swap(LHS, RHS);
// fallthrough
case ICmpInst::ICMP_UGT:
if (SE.isKnownNonNegative(SE.getSCEV(LHS))) {
if (IsNonNegativeAndNotLoopVarying(LHS)) {
Index = RHS;
Length = LHS;
return RANGE_CHECK_BOTH;
@ -328,8 +339,8 @@ InductiveRangeCheck::parseRangeCheck(Loop *L, ScalarEvolution &SE,
if (!ICmpA || !ICmpB)
return InductiveRangeCheck::RANGE_CHECK_UNKNOWN;
auto RCKindA = parseRangeCheckICmp(ICmpA, SE, IndexA, LengthA);
auto RCKindB = parseRangeCheckICmp(ICmpB, SE, IndexB, LengthB);
auto RCKindA = parseRangeCheckICmp(L, ICmpA, SE, IndexA, LengthA);
auto RCKindB = parseRangeCheckICmp(L, ICmpB, SE, IndexB, LengthB);
if (RCKindA == InductiveRangeCheck::RANGE_CHECK_UNKNOWN ||
RCKindB == InductiveRangeCheck::RANGE_CHECK_UNKNOWN)
@ -353,7 +364,7 @@ InductiveRangeCheck::parseRangeCheck(Loop *L, ScalarEvolution &SE,
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Condition)) {
Value *IndexVal = nullptr;
auto RCKind = parseRangeCheckICmp(ICI, SE, IndexVal, Length);
auto RCKind = parseRangeCheckICmp(L, ICI, SE, IndexVal, Length);
if (RCKind == InductiveRangeCheck::RANGE_CHECK_UNKNOWN)
return InductiveRangeCheck::RANGE_CHECK_UNKNOWN;

31
test/Transforms/IRCE/bug-loop-varying-upper-limit.ll Normal file
View File

@ -0,0 +1,31 @@
; RUN: opt -irce-print-changed-loops -S -irce -verify < %s 2>&1 | FileCheck %s
; CHECK-NOT: constrained loop
define void @single_access_no_preloop_no_offset(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
entry:
%first.itr.check = icmp sgt i32 %n, 0
br i1 %first.itr.check, label %loop, label %exit
loop:
%idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds ]
%idx.next = add i32 %idx, 1
%len = load i32, i32* %a_len_ptr, !range !0
%abc = icmp slt i32 %idx, %len
br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
in.bounds:
%addr = getelementptr i32, i32* %arr, i32 %idx
store i32 0, i32* %addr
%next = icmp slt i32 %idx.next, %n
br i1 %next, label %loop, label %exit
out.of.bounds:
ret void
exit:
ret void
}
!0 = !{i32 0, i32 2147483647}
!1 = !{!"branch_weights", i32 64, i32 4}