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[InstCombine] Fix constexpr issue in select combining

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As discussed by Andrea on PR30486, we have an unsafe cast to an Instruction type in the select combine which doesn't take into account that it could be a ConstantExpr instead.

Differential Revision: https://reviews.llvm.org/D25466

llvm-svn: 284000
This commit is contained in:
Simon Pilgrim 2016-10-12 10:20:15 +00:00
parent 9730f4a915
commit 72f99d6988
2 changed files with 49 additions and 4 deletions
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9
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -2271,9 +2271,9 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
SI.getContext(), C.getCaseValue()->getValue().trunc(NewWidth)));
}
Value *Op0 = nullptr;
ConstantInt *AddRHS = nullptr;
if (match(Cond, m_Add(m_Value(), m_ConstantInt(AddRHS)))) {
Instruction *I = cast<Instruction>(Cond);
if (match(Cond, m_Add(m_Value(Op0), m_ConstantInt(AddRHS)))) {
// Change 'switch (X+4) case 1:' into 'switch (X) case -3'.
for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end(); i != e;
++i) {
@ -2289,8 +2289,9 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
"Result of expression should be constant");
i.setValue(cast<ConstantInt>(NewCaseVal));
}
SI.setCondition(I->getOperand(0));
Worklist.Add(I);
SI.setCondition(Op0);
if (auto *CondI = dyn_cast<Instruction>(Cond))
Worklist.Add(CondI);
return &SI;
}

44
test/Transforms/InstCombine/switch-constant-expr.ll Normal file
View File

@ -0,0 +1,44 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
@g = global i32 0
; PR30486
define i32 @single_case() {
; CHECK-LABEL: @single_case(
; CHECK-NEXT: switch i32 ptrtoint (i32* @g to i32), label %x [
; CHECK-NEXT: ]
; CHECK: x:
; CHECK-NEXT: ret i32 0
;
switch i32 add (i32 ptrtoint (i32* @g to i32), i32 -1), label %x []
x:
ret i32 0
}
define i32 @multiple_cases() {
; CHECK-LABEL: @multiple_cases(
; CHECK-NEXT: switch i32 ptrtoint (i32* @g to i32), label %x [
; CHECK-NEXT: i32 2, label %one
; CHECK-NEXT: i32 3, label %two
; CHECK-NEXT: ]
; CHECK: x:
; CHECK-NEXT: ret i32 0
; CHECK: one:
; CHECK-NEXT: ret i32 1
; CHECK: two:
; CHECK-NEXT: ret i32 2
;
switch i32 add (i32 ptrtoint (i32* @g to i32), i32 -1), label %x [
i32 1, label %one
i32 2, label %two
]
x:
ret i32 0
one:
ret i32 1
two:
ret i32 2
}