Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 255177)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -37897,7 +37897,8 @@ rs6000_address_for_fpconvert (rtx x)
 
   gcc_assert (MEM_P (x));
   addr = XEXP (x, 0);
-  if (! legitimate_indirect_address_p (addr, reload_completed)
+  if (can_create_pseudo_p ()
+      && ! legitimate_indirect_address_p (addr, reload_completed)
       && ! legitimate_indexed_address_p (addr, reload_completed))
     {
       if (GET_CODE (addr) == PRE_INC || GET_CODE (addr) == PRE_DEC)
Index: gcc/config/rs6000/rs6000.md
===================================================================
--- gcc/config/rs6000/rs6000.md	(revision 255177)
+++ gcc/config/rs6000/rs6000.md	(working copy)
@@ -14636,6 +14636,9 @@ (define_insn_and_split "float_<mode>si2_
 {
   if (GET_CODE (operands[2]) == SCRATCH)
     operands[2] = gen_reg_rtx (DImode);
+
+  if (MEM_P (operands[1]))
+    operands[1] = rs6000_address_for_fpconvert (operands[1]);
 })
 
 (define_insn_and_split "float<QHI:mode><IEEE128:mode>2"
@@ -14699,6 +14702,9 @@ (define_insn_and_split "floatuns_<mode>s
 {
   if (GET_CODE (operands[2]) == SCRATCH)
     operands[2] = gen_reg_rtx (DImode);
+
+  if (MEM_P (operands[1]))
+    operands[1] = rs6000_address_for_fpconvert (operands[1]);
 })
 
 (define_insn_and_split "floatuns<QHI:mode><IEEE128:mode>2"
Index: gcc/testsuite/gcc.target/powerpc/pr81959.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/pr81959.c	(nonexistent)
+++ gcc/testsuite/gcc.target/powerpc/pr81959.c	(working copy)
@@ -0,0 +1,25 @@
+/* { dg-do compile { target { powerpc64*-*-* && lp64 } } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mpower9-vector -O2 -mfloat128" } */
+
+/* PR 81959, the compiler raised on unrecognizable insn message in converting
+   int to __float128, where the int had a PRE_INC in the address.  */
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE 1024
+#endif
+
+void
+convert_int_to_float128 (__float128 * __restrict__ p,
+			 int * __restrict__ q)
+{
+  unsigned long i;
+
+  for (i = 0; i < ARRAY_SIZE; i++)
+    p[i] = (__float128)q[i];
+}
+
+/* { dg-final { scan-assembler     {\mlfiwax\M|\mlxsiwax\M} } } */
+/* { dg-final { scan-assembler     {\mxscvsdqp\M}           } } */
+/* { dg-final { scan-assembler-not {\mmtvsrd\M}             } } */
+/* { dg-final { scan-assembler-not {\mmtvsrw[sz]\M}         } } */