diff options
Diffstat (limited to 'llvm/lib/CodeGen/MachineInstr.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/MachineInstr.cpp | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp index 52c977a..5860a76 100644 --- a/llvm/lib/CodeGen/MachineInstr.cpp +++ b/llvm/lib/CodeGen/MachineInstr.cpp @@ -1308,11 +1308,28 @@ bool MachineInstr::isSafeToMove(bool &SawStore) const { return false; } + // Don't touch instructions that have non-trivial invariants. For example, + // terminators have to be at the end of a basic block. if (isPosition() || isDebugInstr() || isTerminator() || - mayRaiseFPException() || hasUnmodeledSideEffects() || isJumpTableDebugInfo()) return false; + // Don't touch instructions which can have non-load/store effects. + // + // Inline asm has a "sideeffect" marker to indicate whether the asm has + // intentional side-effects. Even if an inline asm is not "sideeffect", + // though, it still can't be speculatively executed: the operation might + // not be valid on the current target, or for some combinations of operands. + // (Some transforms that move an instruction don't speculatively execute it; + // we currently don't try to handle that distinction here.) + // + // Other instructions handled here include those that can raise FP + // exceptions, x86 "DIV" instructions which trap on divide by zero, and + // stack adjustments. + if (mayRaiseFPException() || hasProperty(MCID::UnmodeledSideEffects) || + isInlineAsm()) + return false; + // See if this instruction does a load. If so, we have to guarantee that the // loaded value doesn't change between the load and the its intended // destination. The check for isInvariantLoad gives the target the chance to |