PR target 78658 exposed a thinko that I had in extending the conversion of
QImode and HImode to floating point.  If the QImode/HImode value was in a
vector register, the pattern didn't allocate the second pseudo register, but
the code generated a reference to that second register.  The second register
was used to move the value from a GPR to the vector registers.

I also modified the zero extend patterns to use ^ instead of ?* like I did on
the November 21st patches so that the register allocator is more likely to
consider using the vector registers if it is useful to do so.

I have done a bootstrap build and make check on a little endian power8 system
and there were no regressions.  Can I check this into the trunk?

[gcc]
2016-12-06  Michael Meissner  <meiss...@linux.vnet.ibm.com>

        PR target/78658
        * config/rs6000/rs6000.md (zero_extendqi<mode>2): Use ^ instead of
        ?* constraints for the ISA 3.0 patterns, so the register allocator
        is more likely to allocate QImode/HImode to vector registers for
        conversion to floating point point unless a reload is needed.
        (zero_extendhi<mode>2): Likewise.
        (float<QHI:mode><FP_ISA3:mode>2_internal): Properly deal with the
        first alternative which is converting QImode/HImode to floating
        point and the QImode/HImode value is in a vector register, and
        does not allocate the second temorary.
        (floatuns<QHI:mode><FP_ISA3:mode>2_internal): Likewise.

[gcc/testsuite]
2016-12-06  Michael Meissner  <meiss...@linux.vnet.ibm.com>

        PR target/78658
        * gcc.target/powerpc/pr78658.c: New test.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
Index: gcc/config/rs6000/rs6000.md
===================================================================
--- gcc/config/rs6000/rs6000.md (revision 243301)
+++ gcc/config/rs6000/rs6000.md (working copy)
@@ -738,8 +738,8 @@ (define_code_attr     SMINMAX       [(smin "SM
 ;; complex forms.  Basic data transfer is done later.
 
 (define_insn "zero_extendqi<mode>2"
-  [(set (match_operand:EXTQI 0 "gpc_reg_operand" "=r,r,?*wJwK,?*wK")
-       (zero_extend:EXTQI (match_operand:QI 1 "reg_or_mem_operand" 
"m,r,Z,*wK")))]
+  [(set (match_operand:EXTQI 0 "gpc_reg_operand" "=r,r,^wJwK,^wK")
+       (zero_extend:EXTQI (match_operand:QI 1 "reg_or_mem_operand" 
"m,r,Z,wK")))]
   ""
   "@
    lbz%U1%X1 %0,%1
@@ -791,7 +791,7 @@ (define_insn_and_split "*zero_extendqi<m
 
 
 (define_insn "zero_extendhi<mode>2"
-  [(set (match_operand:EXTHI 0 "gpc_reg_operand" "=r,r,?*wJwK,?*wK")
+  [(set (match_operand:EXTHI 0 "gpc_reg_operand" "=r,r,^wJwK,^wK")
        (zero_extend:EXTHI (match_operand:HI 1 "reg_or_mem_operand" 
"m,r,Z,wK")))]
   ""
   "@
@@ -5413,8 +5413,11 @@ (define_insn_and_split "*float<QHI:mode>
 
   if (!MEM_P (input))
     {
+      rtx tmp = operands[3];
       if (altivec_register_operand (input, <QHI:MODE>mode))
        emit_insn (gen_extend<QHI:mode>di2 (di, input));
+      else if (GET_CODE (tmp) == SCRATCH)
+       emit_insn (gen_extend<QHI:mode>di2 (di, input));
       else
        {
          rtx tmp = operands[3];
@@ -5449,7 +5452,7 @@ (define_expand "floatuns<QHI:mode><FP_IS
 (define_insn_and_split "*floatuns<QHI:mode><FP_ISA3:mode>2_internal"
   [(set (match_operand:FP_ISA3 0 "vsx_register_operand" "=<Fv>,<Fv>,<Fv>")
        (unsigned_float:FP_ISA3
-        (match_operand:QHI 1 "reg_or_indexed_operand" "wJwK,r,Z")))
+        (match_operand:QHI 1 "reg_or_indexed_operand" "wK,r,Z")))
    (clobber (match_scratch:DI 2 "=wK,wi,wJwK"))
    (clobber (match_scratch:DI 3 "=X,r,X"))]
   "TARGET_P9_VECTOR && TARGET_DIRECT_MOVE && TARGET_POWERPC64
@@ -5467,8 +5470,13 @@ (define_insn_and_split "*floatuns<QHI:mo
   else
     {
       rtx tmp = operands[3];
-      emit_insn (gen_zero_extend<QHI:mode>di2 (tmp, input));
-      emit_move_insn (di, tmp);
+      if (GET_CODE (tmp) == SCRATCH)
+       emit_insn (gen_extend<QHI:mode>di2 (di, input));
+      else
+       {
+         emit_insn (gen_zero_extend<QHI:mode>di2 (tmp, input));
+         emit_move_insn (di, tmp);
+       }
     }
 
   emit_insn (gen_floatdi<FP_ISA3:mode>2 (result, di));
Index: gcc/testsuite/gcc.target/powerpc/pr78658.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/pr78658.c  (revision 0)
+++ gcc/testsuite/gcc.target/powerpc/pr78658.c  (working copy)
@@ -0,0 +1,14 @@
+/* { dg-do compile { target { powerpc64*-*-* && lp64 } } } */
+/* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { 
"-mcpu=power9" } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mcpu=power9 -O2" } */
+
+/* This caused an unrecognizable insn message on development versions of GCC 
7.  */
+
+float a;
+char b;
+
+void c(void)
+{
+  a = b = a;
+}

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