Disable generation of scalar modulo instructions.

It was recently discovered that the scalar modulo instructions can suffer
noticeable performance issues for certain input values. This patch disables
their generation since the equivalent div/mul/sub sequence does not suffer
the same problem.

gcc/
	* config/rs6000/rs6000.cc (rs6000_rtx_costs): Check whether the
	modulo instruction is disabled.
	* config/rs6000/rs6000.h (RS6000_DISABLE_SCALAR_MODULO): New.
	* config/rs6000/rs6000.md (mod<mode>3, *mod<mode>3): Check it.
	(define_expand umod<mode>3): New.
	(define_insn umod<mode>3): Rename to *umod<mode>3 and check if the modulo
	instruction is disabled.
	(umodti3, modti3): Check if the modulo instruction is disabled.

gcc/testsuite/
	* gcc.target/powerpc/clone1.c: Add xfails.
	* gcc.target/powerpc/clone3.c: Likewise.
	* gcc.target/powerpc/mod-1.c: Update scan strings and add xfails.
	* gcc.target/powerpc/mod-2.c: Likewise.
	* gcc.target/powerpc/p10-vdivq-vmodq.c: Add xfails.

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index efe9adce1f8b21e381cd38baee3fe45f5eea1631..caf9eeee5ef1897feb9119971beea141b8b7942d 100644 (file)
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -22164,7 +22164,9 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int outer_code,
            *total = rs6000_cost->divsi;
        }
       /* Add in shift and subtract for MOD unless we have a mod instruction. */
-      if (!TARGET_MODULO && (code == MOD || code == UMOD))
+      if ((!TARGET_MODULO
+          || (RS6000_DISABLE_SCALAR_MODULO && SCALAR_INT_MODE_P (mode)))
+        && (code == MOD || code == UMOD))
        *total += COSTS_N_INSNS (2);
       return false;
 

diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index 3503614efbd6306f4e4bf23ed730dccf73da6aa7..22595f6ebd779c91eb00dfeec584b3f32b28d7d0 100644 (file)
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -2492,3 +2492,9 @@ while (0)
        rs6000_asm_output_opcode (STREAM);                              \
     }                                                                  \
   while (0)
+
+/* Disable generation of scalar modulo instructions due to performance issues
+   with certain input values.  This can be removed in the future when the
+   issues have been resolved.  */
+#define RS6000_DISABLE_SCALAR_MODULO 1
+

diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 1a9a7b1a47918f39fc91038607f21a8ba9a2e740..7b583d7a69ad9d8393584e324db9f1bf33c92d91 100644 (file)
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -3424,6 +3424,17 @@
        FAIL;
 
       operands[2] = force_reg (<MODE>mode, operands[2]);
+
+      if (RS6000_DISABLE_SCALAR_MODULO)
+       {
+         temp1 = gen_reg_rtx (<MODE>mode);
+         temp2 = gen_reg_rtx (<MODE>mode);
+
+         emit_insn (gen_div<mode>3 (temp1, operands[1], operands[2]));
+         emit_insn (gen_mul<mode>3 (temp2, temp1, operands[2]));
+         emit_insn (gen_sub<mode>3 (operands[0], operands[1], temp2));
+         DONE;
+       }
     }
   else
     {
@@ -3443,17 +3454,36 @@
   [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r,r")
         (mod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r,r")
                 (match_operand:GPR 2 "gpc_reg_operand" "r,r")))]
-  "TARGET_MODULO"
+  "TARGET_MODULO && !RS6000_DISABLE_SCALAR_MODULO"
   "mods<wd> %0,%1,%2"
   [(set_attr "type" "div")
    (set_attr "size" "<bits>")])
 
+;; This define_expand can be removed when RS6000_DISABLE_SCALAR_MODULO is
+;; removed.
+(define_expand "umod<mode>3"
+  [(set (match_operand:GPR 0 "gpc_reg_operand")
+       (umod:GPR (match_operand:GPR 1 "gpc_reg_operand")
+                 (match_operand:GPR 2 "gpc_reg_operand")))]
+  "TARGET_MODULO"
+{
+  if (RS6000_DISABLE_SCALAR_MODULO)
+    {
+      rtx temp1 = gen_reg_rtx (<MODE>mode);
+      rtx temp2 = gen_reg_rtx (<MODE>mode);
+
+      emit_insn (gen_udiv<mode>3 (temp1, operands[1], operands[2]));
+      emit_insn (gen_mul<mode>3 (temp2, temp1, operands[2]));
+      emit_insn (gen_sub<mode>3 (operands[0], operands[1], temp2));
+      DONE;
+    }
+})
 
-(define_insn "umod<mode>3"
+(define_insn "*umod<mode>3"
   [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r,r")
         (umod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r,r")
                  (match_operand:GPR 2 "gpc_reg_operand" "r,r")))]
-  "TARGET_MODULO"
+  "TARGET_MODULO && !RS6000_DISABLE_SCALAR_MODULO"
   "modu<wd> %0,%1,%2"
   [(set_attr "type" "div")
    (set_attr "size" "<bits>")])
@@ -3510,7 +3540,7 @@
   [(set (match_operand:TI 0 "altivec_register_operand" "=v")
        (umod:TI (match_operand:TI 1 "altivec_register_operand" "v")
                 (match_operand:TI 2 "altivec_register_operand" "v")))]
-  "TARGET_POWER10 && TARGET_POWERPC64"
+  "TARGET_POWER10 && TARGET_POWERPC64 && !RS6000_DISABLE_SCALAR_MODULO"
   "vmoduq %0,%1,%2"
   [(set_attr "type" "vecdiv")
    (set_attr "size" "128")])
@@ -3519,7 +3549,7 @@
   [(set (match_operand:TI 0 "altivec_register_operand" "=v")
        (mod:TI (match_operand:TI 1 "altivec_register_operand" "v")
                (match_operand:TI 2 "altivec_register_operand" "v")))]
-  "TARGET_POWER10 && TARGET_POWERPC64"
+  "TARGET_POWER10 && TARGET_POWERPC64 && !RS6000_DISABLE_SCALAR_MODULO"
   "vmodsq %0,%1,%2"
   [(set_attr "type" "vecdiv")
    (set_attr "size" "128")])

diff --git a/gcc/testsuite/gcc.target/powerpc/clone1.c b/gcc/testsuite/gcc.target/powerpc/clone1.c
index c69fd2aa1b87e20548771e592d63e0a32bb247d1..74323ca0e8c125a033b80b3cdd293ad3656f5ef9 100644 (file)
--- a/gcc/testsuite/gcc.target/powerpc/clone1.c
+++ b/gcc/testsuite/gcc.target/powerpc/clone1.c
@@ -21,6 +21,7 @@ long mod_func_or (long a, long b, long c)
   return mod_func (a, b) | c;
 }
 
-/* { dg-final { scan-assembler-times {\mdivd\M}  1 } } */
-/* { dg-final { scan-assembler-times {\mmulld\M} 1 } } */
-/* { dg-final { scan-assembler-times {\mmodsd\M} 1 } } */
+/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
+/* { dg-final { scan-assembler-times {\mdivd\M}  1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmulld\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmodsd\M} 1 { xfail *-*-* } } } */

diff --git a/gcc/testsuite/gcc.target/powerpc/clone3.c b/gcc/testsuite/gcc.target/powerpc/clone3.c
index 911b88b781d16e984460f5bb71140f9f6ffd7b78..d3eb4dd2378c06652818baabdf7d490325942f45 100644 (file)
--- a/gcc/testsuite/gcc.target/powerpc/clone3.c
+++ b/gcc/testsuite/gcc.target/powerpc/clone3.c
@@ -27,7 +27,8 @@ long mod_func_or (long a, long b, long c)
   return mod_func (a, b) | c;
 }
 
-/* { dg-final { scan-assembler-times {\mdivd\M}  1 } } */
-/* { dg-final { scan-assembler-times {\mmulld\M} 1 } } */
-/* { dg-final { scan-assembler-times {\mmodsd\M} 2 } } */
+/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
+/* { dg-final { scan-assembler-times {\mdivd\M}  1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmulld\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmodsd\M} 2 { xfail *-*-* } } } */
 /* { dg-final { scan-assembler-times {\mpld\M}   1 } } */

diff --git a/gcc/testsuite/gcc.target/powerpc/mod-1.c b/gcc/testsuite/gcc.target/powerpc/mod-1.c
index 861ba670af4ded0a9ae3edb7081dd2e91f0a760b..8720ffb33460e57871779d7fe725b8f3333db82e 100644 (file)
--- a/gcc/testsuite/gcc.target/powerpc/mod-1.c
+++ b/gcc/testsuite/gcc.target/powerpc/mod-1.c
@@ -7,13 +7,14 @@ long lsmod (long a, long b) { return a%b; }
 unsigned int iumod (unsigned int a, unsigned int b) { return a%b; }
 unsigned long lumod (unsigned long a, unsigned long b) { return a%b; }
 
-/* { dg-final { scan-assembler-times "modsw " 1 } } */
-/* { dg-final { scan-assembler-times "modsd " 1 } } */
-/* { dg-final { scan-assembler-times "moduw " 1 } } */
-/* { dg-final { scan-assembler-times "modud " 1 } } */
-/* { dg-final { scan-assembler-not   "mullw "   } } */
-/* { dg-final { scan-assembler-not   "mulld "   } } */
-/* { dg-final { scan-assembler-not   "divw "    } } */
-/* { dg-final { scan-assembler-not   "divd "    } } */
-/* { dg-final { scan-assembler-not   "divwu "   } } */
-/* { dg-final { scan-assembler-not   "divdu "   } } */
+/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
+/* { dg-final { scan-assembler-times {\mmodsw\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmodsd\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmoduw\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmodud\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mmullw\M}   { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mmulld\M}   { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivw\M}    { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivd\M}    { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivwu\M}   { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivdu\M}   { xfail *-*-* } } } */

diff --git a/gcc/testsuite/gcc.target/powerpc/mod-2.c b/gcc/testsuite/gcc.target/powerpc/mod-2.c
index 441ec5878f1c06a2f2b79c45fd9422492da93c57..54bdca886078ecf3b7f9090cc4607696aa9c539b 100644 (file)
--- a/gcc/testsuite/gcc.target/powerpc/mod-2.c
+++ b/gcc/testsuite/gcc.target/powerpc/mod-2.c
@@ -5,8 +5,9 @@
 int ismod (int a, int b) { return a%b; }
 unsigned int iumod (unsigned int a, unsigned int b) { return a%b; }
 
-/* { dg-final { scan-assembler-times "modsw " 1 } } */
-/* { dg-final { scan-assembler-times "moduw " 1 } } */
-/* { dg-final { scan-assembler-not   "mullw "   } } */
-/* { dg-final { scan-assembler-not   "divw "    } } */
-/* { dg-final { scan-assembler-not   "divwu "   } } */
+/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
+/* { dg-final { scan-assembler-times {\mmodsw\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-times {\mmoduw\M} 1 { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mmullw\M}   { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivw\M}    { xfail *-*-* } } } */
+/* { dg-final { scan-assembler-not   {\mdivwu\M}   { xfail *-*-* } } } */

diff --git a/gcc/testsuite/gcc.target/powerpc/p10-vdivq-vmodq.c b/gcc/testsuite/gcc.target/powerpc/p10-vdivq-vmodq.c
index 84685e5ff430d22d9c498f245b639d117bdfbbe7..148998c8c9d684fd51deee099bf104b07b5f2ed0 100644 (file)
--- a/gcc/testsuite/gcc.target/powerpc/p10-vdivq-vmodq.c
+++ b/gcc/testsuite/gcc.target/powerpc/p10-vdivq-vmodq.c
@@ -23,5 +23,6 @@ __int128 s_mod(__int128 a, __int128 b)
 
 /* { dg-final { scan-assembler {\mvdivsq\M} } } */
 /* { dg-final { scan-assembler {\mvdivuq\M} } } */
-/* { dg-final { scan-assembler {\mvmodsq\M} } } */
-/* { dg-final { scan-assembler {\mvmoduq\M} } } */
+/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
+/* { dg-final { scan-assembler {\mvmodsq\M} { xfail *-*-* } } } */
+/* { dg-final { scan-assembler {\mvmoduq\M} { xfail *-*-* } } } */