[ARM] Don't confuse the scheduler for very large VLDMDIA etc.

ARMBaseInstrInfo::getNumLDMAddresses is making bad assumptions about the
memory operands of load and store-multiple operations.  This doesn't
really fix the problem properly, but it's enough to prevent crashing,
at least.

Fixes https://bugs.llvm.org/show_bug.cgi?id=41231 .

Differential Revision: https://reviews.llvm.org/D59834

llvm-svn: 357109

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
index bb222edbcef..bc4547c996f 100644
--- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -3435,7 +3435,12 @@ unsigned ARMBaseInstrInfo::getNumLDMAddresses(const MachineInstr &MI) const {
        I != E; ++I) {
     Size += (*I)->getSize();
   }
-  return Size / 4;
+  // FIXME: The scheduler currently can't handle values larger than 16. But
+  // the values can actually go up to 32 for floating-point load/store
+  // multiple (VLDMIA etc.). Also, the way this code is reasoning about memory
+  // operations isn't right; we could end up with "extra" memory operands for
+  // various reasons, like tail merge merging two memory operations.
+  return std::min(Size / 4, 16U);
 }
 
 static unsigned getNumMicroOpsSingleIssuePlusExtras(unsigned Opc,