commit 920189bd8d86f3035573c51a86f693a2dce4f837
author Peter Collingbourne <pcc@google.com> Fri Jan 22 17:42:36 2021 -0800
committer Jacob Bramley <jacob.bramley@arm.com> Wed Feb 03 11:37:23 2021 +0000
tree 7baf4acac28a5cccbd1d556c3c3ad1eb20a9d2c1
parent 852d12ca548919a23a3dbeb32751552ce0ad50f3

Fix invalid encoding for single register push/pop.

LDMIA/STMDB are CONSTRAINED UNPREDICTABLE when used with a single
register argument. In such cases, encode a single-register push/pop
instead.

src/aarch32/macro-assembler-aarch32.h

diff --git a/src/aarch32/macro-assembler-aarch32.h b/src/aarch32/macro-assembler-aarch32.h
index 6d76642..62c116d 100644
--- a/src/aarch32/macro-assembler-aarch32.h
+++ b/src/aarch32/macro-assembler-aarch32.h
@@ -2897,7 +2897,12 @@
     VIXL_ASSERT(OutsideITBlock());
     MacroEmissionCheckScope guard(this);
     ITScope it_scope(this, &cond, guard);
-    pop(cond, registers);
+    if (registers.IsSingleRegister() &&
+        (!IsUsingT32() || !registers.IsR0toR7orPC())) {
+      pop(cond, registers.GetFirstAvailableRegister());
+    } else if (!registers.IsEmpty()) {
+      pop(cond, registers);
+    }
   }
   void Pop(RegisterList registers) { Pop(al, registers); }
 
@@ -2917,7 +2922,12 @@
     VIXL_ASSERT(OutsideITBlock());
     MacroEmissionCheckScope guard(this);
     ITScope it_scope(this, &cond, guard);
-    push(cond, registers);
+    if (registers.IsSingleRegister() &&
+        (!IsUsingT32() || !registers.IsR0toR7orLR())) {
+      push(cond, registers.GetFirstAvailableRegister());
+    } else if (!registers.IsEmpty()) {
+      push(cond, registers);
+    }
   }
   void Push(RegisterList registers) { Push(al, registers); }