[InlineSpiller] Don't call TargetInstrInfo::foldMemoryOperand with an…

… empty list.

Since r287792 if we try to do that we will hit an assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289001 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/InlineSpiller.cpp

@@ -768,6 +768,11 @@ foldMemoryOperand(ArrayRef<std::pair<MachineInstr*, unsigned> > Ops,
       FoldOps.push_back(Idx);
   }
 
+  // If we only have implicit uses, we won't be able to fold that.
+  // Moreover, TargetInstrInfo::foldMemoryOperand will assert if we try!
+  if (FoldOps.empty())
+    return false;
+
   MachineInstrSpan MIS(MI);
 
   MachineInstr *FoldMI =

test/CodeGen/X86/implicit-use-spill.mir

@@ -0,0 +1,22 @@
+# RUN: llc -run-pass=greedy -mtriple=x86_64-apple-macosx -o - %s 2>&1 | FileCheck %s
+
+# Make sure we don't assert when we try to reload a value that is just implicitly used.
+---
+# CHECK: name: foo
+# This test forces a spill of %0.
+name: foo
+registers:
+  - { id: 0, class: gr64 }
+body: |
+  bb.0:
+  ; CHECK: NOOP implicit-def [[VAL:%[0-9]+]]
+  ; VAL should be spilled before csr_noregs, i.e., before we clobber all the registers
+  ; CHECK-NEXT: MOV64mr [[SLOT:%stack.[0-9]+]], 1, _, 0, _, [[VAL]]
+  ; CHECK-NEXT: NOOP csr_noregs
+  ; We need to reload before the (implicit) use.
+  ; CHECK-NEXT: [[RELOADED_VAL:%[0-9]+]] = MOV64rm [[SLOT]], 1, _, 0, _
+  ; CHECK-NEXT: NOOP implicit [[RELOADED_VAL]]
+  NOOP implicit-def %0
+  NOOP csr_noregs
+  NOOP implicit %0
+...