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Don't attempt to divide INT_MIN by -1; consider such cases to

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have overflowed.

llvm-svn: 96428
This commit is contained in:
Dan Gohman 2010-02-17 00:41:53 +00:00
parent 9625fb062a
commit 493a1fcbe0
2 changed files with 30 additions and 0 deletions
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4
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -2112,12 +2112,16 @@ void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
Formula F = Base;
// Check that the multiplication doesn't overflow.
if (F.AM.BaseOffs == INT64_MIN && Factor == -1)
continue;
F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
if ((int64_t)F.AM.BaseOffs / Factor != Base.AM.BaseOffs)
continue;
// Check that multiplying with the use offset doesn't overflow.
int64_t Offset = LU.MinOffset;
if (Offset == INT64_MIN && Factor == -1)
continue;
Offset = (uint64_t)Offset * Factor;
if ((int64_t)Offset / Factor != LU.MinOffset)
continue;

26
test/CodeGen/X86/lsr-overflow.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: llc < %s -march=x86-64 | FileCheck %s
; The comparison uses the pre-inc value, which could lead LSR to
; try to compute -INT64_MIN.
; CHECK: movabsq $-9223372036854775808, %rax ## imm = 0x8000000000000000
; CHECK: cmpq %rax, %rbx
; CHECK: sete %al
declare i64 @bar()
define i1 @foo() nounwind {
entry:
br label %for.cond.i
for.cond.i:
%indvar = phi i64 [ 0, %entry ], [ %indvar.next, %for.cond.i ]
%t = call i64 @bar()
%indvar.next = add i64 %indvar, 1
%s = icmp ne i64 %indvar.next, %t
br i1 %s, label %for.cond.i, label %__ABContainsLabel.exit
__ABContainsLabel.exit:
%cmp = icmp eq i64 %indvar, 9223372036854775807
ret i1 %cmp
}