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[ARM] t2_so_imm_neg had a subtle bug in the conversion, and could trigger UB by negating (int)-2147483648. By pure luck, none of the pre-existing tests triggered this; so I'm adding one.

Browse Source 
Summary: Thanks to Vitaly Buka for helping catch this.

Reviewers: rengolin, jmolloy, efriedma, vitalybuka

Subscribers: llvm-commits, aemerson

Differential Revision: https://reviews.llvm.org/D31242

llvm-svn: 298512
This commit is contained in:
Artyom Skrobov 2017-03-22 15:09:30 +00:00
parent 51a1f661a4
commit 5e7c493374
2 changed files with 12 additions and 1 deletions
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4
lib/Target/ARM/ARMInstrThumb2.td
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@ -111,7 +111,9 @@ def t2_so_imm_notSext : Operand<i32>, PatLeaf<(imm), [{
// t2_so_imm_neg - Match an immediate that is a negation of a t2_so_imm.
def t2_so_imm_neg_asmoperand : AsmOperandClass { let Name = "T2SOImmNeg"; }
def t2_so_imm_neg : Operand<i32>, PatLeaf<(imm), [{
int64_t Value = -(int)N->getZExtValue();
int64_t Value = N->getZExtValue();
if (Value == 1LL<<31) return false; // INT_MIN cannot be negated
Value = -(int)Value;
return Value && ARM_AM::getT2SOImmVal(Value) != -1;
}], t2_so_imm_neg_XFORM> {
let ParserMatchClass = t2_so_imm_neg_asmoperand;

9
test/CodeGen/Thumb/ispositive.ll
View File

@ -9,3 +9,12 @@ entry:
ret i32 %1
}
define i32 @test2(i32 %X) {
entry:
; CHECK-LABEL: test2:
; CHECK: lsls r1, r1, #31
; CHECK-NEXT: adds
%tmp1 = sub i32 %X, 2147483648
ret i32 %tmp1
}