[PATCH] V11 patch #3 of 15, Use 'Q' constraint for variable vector extract from memory

[Michael Meissner]

As I mentioned in the intro, for the case where we are optimizing the extract
of a variable element from a vector in memory, the current code takes a regular
address, and the temporary that holds the byte offset, and tries to generate a
new address.  In particular, it failed when the vector was a PC-relative
address, because it didn't have enough temporary registers, and it used the
temporary to hold the byte offset to hold the address.

Initially in doing these patches, I reworked the constraints for prefixed and
non-prefixed memory so we could identify when we needed a second temporary.
Then I realized that eventaully we will want to generate an X-FORM (register +
register) address, and it was just simpler to use the 'Q' constraint, and have
the register allocator put the address into a register.

I have verified that the bug is indeed fixed (patch #15 will include the new
tests for this).  I have also bootstrapped the compiler on a little endian
power8 machine and there were no regressions in the test suite.  Can I check
this patch into the trunk?

2019-12-20  Michael Meissner  <meissner@linux.ibm.com>

	* config/rs6000/vsx.md (vsx_extract_<mode>_var, VSX_D iterator):
	Use 'Q' for memory constraints because we need to do an X-FORM
	load with the variable index.
	(vsx_extract_v4sf_var): Use 'Q' for memory constraints because we
	need to do an X-FORM load with the variable index.
	(vsx_extract_<mode>_var, VSX_EXTRACT_I iterator):Use 'Q' for
	memory constraints because we need to do an X-FORM load with the
	variable index.
	(vsx_extract_<mode>_<VS_scalar>mode_var): Use 'Q' for memory
	constraints because we need to do an X-FORM load with the variable
	index.

Index: gcc/config/rs6000/vsx.md
===================================================================
--- gcc/config/rs6000/vsx.md	(revision 279597)
+++ gcc/config/rs6000/vsx.md	(working copy)
@@ -3245,10 +3245,11 @@ (define_insn "vsx_vslo_<mode>"
   "vslo %0,%1,%2"
   [(set_attr "type" "vecperm")])
 
-;; Variable V2DI/V2DF extract
+;; Variable V2DI/V2DF extract.  Use 'Q' for the memory because we will
+;; ultimately have to convert the address into base + index.
 (define_insn_and_split "vsx_extract_<mode>_var"
   [(set (match_operand:<VS_scalar> 0 "gpc_reg_operand" "=v,wa,r")
-	(unspec:<VS_scalar> [(match_operand:VSX_D 1 "input_operand" "v,m,m")
+	(unspec:<VS_scalar> [(match_operand:VSX_D 1 "input_operand" "v,Q,Q")
 			     (match_operand:DI 2 "gpc_reg_operand" "r,r,r")]
 			    UNSPEC_VSX_EXTRACT))
    (clobber (match_scratch:DI 3 "=r,&b,&b"))
@@ -3318,7 +3319,7 @@ (define_insn_and_split "*vsx_extract_v4s
 ;; Variable V4SF extract
 (define_insn_and_split "vsx_extract_v4sf_var"
   [(set (match_operand:SF 0 "gpc_reg_operand" "=wa,wa,?r")
-	(unspec:SF [(match_operand:V4SF 1 "input_operand" "v,m,m")
+	(unspec:SF [(match_operand:V4SF 1 "input_operand" "v,Q,Q")
 		    (match_operand:DI 2 "gpc_reg_operand" "r,r,r")]
 		   UNSPEC_VSX_EXTRACT))
    (clobber (match_scratch:DI 3 "=r,&b,&b"))
@@ -3681,7 +3682,7 @@ (define_insn_and_split "*vsx_extract_<mo
 (define_insn_and_split "vsx_extract_<mode>_var"
   [(set (match_operand:<VS_scalar> 0 "gpc_reg_operand" "=r,r,r")
 	(unspec:<VS_scalar>
-	 [(match_operand:VSX_EXTRACT_I 1 "input_operand" "v,v,m")
+	 [(match_operand:VSX_EXTRACT_I 1 "input_operand" "v,v,Q")
 	  (match_operand:DI 2 "gpc_reg_operand" "r,r,r")]
 	 UNSPEC_VSX_EXTRACT))
    (clobber (match_scratch:DI 3 "=r,r,&b"))
@@ -3701,7 +3702,7 @@ (define_insn_and_split "*vsx_extract_<mo
   [(set (match_operand:<VS_scalar> 0 "gpc_reg_operand" "=r,r,r")
 	(zero_extend:<VS_scalar>
 	 (unspec:<VSX_EXTRACT_I:VS_scalar>
-	  [(match_operand:VSX_EXTRACT_I 1 "input_operand" "v,v,m")
+	  [(match_operand:VSX_EXTRACT_I 1 "input_operand" "v,v,Q")
 	   (match_operand:DI 2 "gpc_reg_operand" "r,r,r")]
 	  UNSPEC_VSX_EXTRACT)))
    (clobber (match_scratch:DI 3 "=r,r,&b"))

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797