diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index fd6f4ba476e..0039d1eebc0 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3837,6 +3837,28 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal, if (Value *V = simplifySelectBitTest(TrueVal, FalseVal, X, Y, Pred == ICmpInst::ICMP_EQ)) return V; + + // Test for zero-shift-guard-ops around funnel shifts. These are used to + // avoid UB from oversized shifts in raw IR rotate patterns, but the + // intrinsics do not have that problem. + Value *ShAmt; + auto isFsh = m_CombineOr(m_Intrinsic<Intrinsic::fshl>(m_Value(X), m_Value(), + m_Value(ShAmt)), + m_Intrinsic<Intrinsic::fshr>(m_Value(), m_Value(X), + m_Value(ShAmt))); + // (ShAmt != 0) ? fshl(X, *, ShAmt) : X --> fshl(X, *, ShAmt) + // (ShAmt != 0) ? fshr(*, X, ShAmt) : X --> fshr(*, X, ShAmt) + // (ShAmt == 0) ? fshl(X, *, ShAmt) : X --> X + // (ShAmt == 0) ? fshr(*, X, ShAmt) : X --> X + if (match(TrueVal, isFsh) && FalseVal == X && CmpLHS == ShAmt) + return Pred == ICmpInst::ICMP_NE ? TrueVal : X; + + // (ShAmt == 0) ? X : fshl(X, *, ShAmt) --> fshl(X, *, ShAmt) + // (ShAmt == 0) ? X : fshr(*, X, ShAmt) --> fshr(*, X, ShAmt) + // (ShAmt != 0) ? X : fshl(X, *, ShAmt) --> X + // (ShAmt != 0) ? X : fshr(*, X, ShAmt) --> X + if (match(FalseVal, isFsh) && TrueVal == X && CmpLHS == ShAmt) + return Pred == ICmpInst::ICMP_EQ ? FalseVal : X; } // Check for other compares that behave like bit test. |
