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Reapply: [InstCombine] Fix visitSwitchInst to use right operand types for sub cstexpr

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The visitSwitchInst generates SUB constant expressions to recompute the
switch condition. When truncating the condition to a smaller type, SUB
expressions should use the previous type (before trunc) for both
operands. Also, fix code to also return the modified switch when only
the truncation is performed.

This fixes an assertion crash.

Differential Revision: http://reviews.llvm.org/D6644

rdar://problem/19191835

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224588 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes 2014-12-19 17:12:35 +00:00
parent b8b0b8f0a8
commit 06833ca7c1
2 changed files with 40 additions and 3 deletions
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13
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -2095,8 +2095,10 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
// the largest legal integer type. We need to be conservative here since
// x86 generates redundant zero-extenstion instructions if the operand is
// truncated to i8 or i16.
bool TruncCond = false;
if (DL && BitWidth > NewWidth &&
NewWidth >= DL->getLargestLegalIntTypeSize()) {
TruncCond = true;
IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
Builder->SetInsertPoint(&SI);
Value *NewCond = Builder->CreateTrunc(SI.getCondition(), Ty, "trunc");
@ -2115,8 +2117,12 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
i != e; ++i) {
ConstantInt* CaseVal = i.getCaseValue();
Constant* NewCaseVal = ConstantExpr::getSub(cast<Constant>(CaseVal),
AddRHS);
Constant *LHS = CaseVal;
if (TruncCond)
LHS = LeadingKnownZeros
? ConstantExpr::getZExt(CaseVal, Cond->getType())
: ConstantExpr::getSExt(CaseVal, Cond->getType());
Constant* NewCaseVal = ConstantExpr::getSub(LHS, AddRHS);
assert(isa<ConstantInt>(NewCaseVal) &&
"Result of expression should be constant");
i.setValue(cast<ConstantInt>(NewCaseVal));
@ -2126,7 +2132,8 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
return &SI;
}
}
return nullptr;
return TruncCond ? &SI : nullptr;
}
Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {

30
test/Transforms/InstCombine/narrow-switch.ll
View File

@ -91,3 +91,33 @@ return:
%retval.0 = phi i32 [ 24, %sw.default ], [ 123, %sw.bb2 ], [ 213, %sw.bb1 ], [ 231, %entry ]
ret i32 %retval.0
}
; Make sure to avoid assertion crashes and use the type before
; truncation to generate the sub constant expressions that leads
; to the recomputed condition.
;
; CHECK-LABEL: @trunc64to59
; CHECK: switch i59
; CHECK: i59 0, label
; CHECK: i59 18717182647723699, label
define void @trunc64to59(i64 %a) {
entry:
%tmp0 = and i64 %a, 15
%tmp1 = mul i64 %tmp0, -6425668444178048401
%tmp2 = add i64 %tmp1, 5170979678563097242
%tmp3 = mul i64 %tmp2, 1627972535142754813
switch i64 %tmp3, label %sw.default [
i64 847514119312061490, label %sw.bb1
i64 866231301959785189, label %sw.bb2
]
sw.bb1:
br label %sw.default
sw.bb2:
br label %sw.default
sw.default:
ret void
}