diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index 0dde18522f4..bc9574221b3 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1010,6 +1010,8 @@ static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2, return true; } +static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I); + /// HoistThenElseCodeToIf - Given a conditional branch that goes to BB1 and /// BB2, hoist any common code in the two blocks up into the branch block. The /// caller of this function guarantees that BI's block dominates BB1 and BB2. @@ -1094,6 +1096,12 @@ HoistTerminator: if (BB1V == BB2V) continue; + // Check for passingValueIsAlwaysUndefined here because we would rather + // eliminate undefined control flow then converting it to a select. + if (passingValueIsAlwaysUndefined(BB1V, PN) || + passingValueIsAlwaysUndefined(BB2V, PN)) + return Changed; + if (isa<ConstantExpr>(BB1V) && !isSafeToSpeculativelyExecute(BB1V, DL)) return Changed; if (isa<ConstantExpr>(BB2V) && !isSafeToSpeculativelyExecute(BB2V, DL)) @@ -1508,6 +1516,11 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, if (ThenV == OrigV) continue; + // Don't convert to selects if we could remove undefined behavior instead. + if (passingValueIsAlwaysUndefined(OrigV, PN) || + passingValueIsAlwaysUndefined(ThenV, PN)) + return false; + HaveRewritablePHIs = true; ConstantExpr *OrigCE = dyn_cast<ConstantExpr>(OrigV); ConstantExpr *ThenCE = dyn_cast<ConstantExpr>(ThenV); |
