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[SimplifyCFG] Fix nasty RAUW bug from r277325 

Using RAUW was wrong here; if we have a switch transform such as:
  18 -> 6 then
  6 -> 0

If we use RAUW, while performing the second transform the  *transformed* 6
from the first will be also replaced, so we end up with:
  18 -> 0
  6 -> 0

Found by clang stage2 bootstrap; testcase added.

llvm-svn: 277332
This commit is contained in:
James Molloy 2016-08-01 09:34:48 +00:00
parent ab5a4c7dbb
commit bade86cedc
2 changed files with 31 additions and 4 deletions
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7
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -5132,11 +5132,12 @@ static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
Builder.CreateShl(Sub, Ty->getBitWidth() - Shift));
SI->replaceUsesOfWith(SI->getCondition(), Rot);
for (auto &C : SI->cases()) {
for (SwitchInst::CaseIt C = SI->case_begin(), E = SI->case_end(); C != E;
++C) {
auto *Orig = C.getCaseValue();
auto Sub = Orig->getValue() - APInt(Ty->getBitWidth(), Base);
SI->replaceUsesOfWith(Orig,
ConstantInt::get(Ty, Sub.lshr(ShiftC->getValue())));
C.setValue(
cast<ConstantInt>(ConstantInt::get(Ty, Sub.lshr(ShiftC->getValue()))));
}
return true;
}

26
llvm/test/Transforms/SimplifyCFG/rangereduce.ll
View File

@ -193,3 +193,29 @@ two:
three:
ret i32 99783
}
; CHECK-LABEL: @test9
; CHECK: switch
; CHECK: i32 6
; CHECK: i32 7
; CHECK: i32 0
; CHECK: i32 2
define i32 @test9(i32 %a) {
switch i32 %a, label %def [
i32 18, label %one
i32 20, label %two
i32 6, label %three
i32 10, label %three
]
def:
ret i32 8867
one:
ret i32 11984
two:
ret i32 1143
three:
ret i32 99783
}