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.

8 files changed, 72 insertions, 29 deletions

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index efe9adc..caf9eee 100644
--- 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 3503614..22595f6 100644
--- 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 1a9a7b1..7b583d7 100644
--- 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 c69fd2a..74323ca 100644
--- 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 911b88b..d3eb4dd 100644
--- 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 861ba67..8720ffb 100644
--- 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 441ec58..54bdca8 100644
--- 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 84685e5..148998c 100644
--- 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 *-*-* } } } */