Do not model all INLINEASM instructions as having unmodelled side effects.
Instead encode llvm IR level property "HasSideEffects" in an operand (shared
with IsAlignStack). Added MachineInstrs::hasUnmodeledSideEffects() to check
the operand when the instruction is an INLINEASM.
This allows memory instructions to be moved around INLINEASM instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123044 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/DeadMachineInstructionElim.cpp b/lib/CodeGen/DeadMachineInstructionElim.cpp
index 786de1b..32040e5 100644
--- a/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -54,6 +54,12 @@
}
bool DeadMachineInstructionElim::isDead(const MachineInstr *MI) const {
+ // Technically speaking inline asm without side effects and no defs can still
+ // be deleted. But there is so much bad inline asm code out there, we should
+ // let them be.
+ if (MI->isInlineAsm())
+ return false;
+
// Don't delete instructions with side effects.
bool SawStore = false;
if (!MI->isSafeToMove(TII, 0, SawStore) && !MI->isPHI())