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Fix for incorrect address sinking in the presence of potential overflows.

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In some cases it is possible for CGP to attempt to reuse a base address from
another basic block. In those cases we have to be sure that all the address
math was either done at the same bit width, or that none of it overflowed
before it was extended.

Patch by Louis Gerbarg <lgg@apple.com>

rdar://16307442

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204833 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach
2014-03-26 17:27:01 +00:00
parent b82f8a28e8
commit 489752ddb4
2 changed files with 34 additions and 1 deletions
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lib/CodeGen/CodeGenPrepare.cpp
+8 -1
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@@ -2438,7 +2438,14 @@ bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
cast<IntegerType>(V->getType())->getBitWidth()) {
V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
} else {
V = Builder.CreateSExt(V, IntPtrTy, "sunkaddr");
// It is only safe to sign extend the BaseReg if we know that the math
// required to create it did not overflow before we extend it. Since
// the original IR value was tossed in favor of a constant back when
// the AddrMode was created we need to bail out gracefully if widths
// do not match instead of extending it.
if (Result != AddrMode.BaseReg)
cast<Instruction>(Result)->eraseFromParent();
return false;
}
if (AddrMode.Scale != 1)
V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),