[gcc r14-6391] rs6000: Enable lrint<mode>si2 on old archs with stfiwx enabled

[HaoChen Gui]

https://gcc.gnu.org/g:46e342b985e6b4058db73875103cced2666e84e2

commit r14-6391-g46e342b985e6b4058db73875103cced2666e84e2
Author: Haochen Gui <guihaoc@gcc.gnu.org>
Date:   Mon Dec 11 08:40:34 2023 +0800

    rs6000: Enable lrint<mode>si2 on old archs with stfiwx enabled
    
    The powerpc 32-bit processors (e.g. 5470) supports "fctiw" instruction,
    but the instruction can't be generated on such platforms as the insn is
    guard by TARGET_POPCNTD.  The root cause is SImode in float register is
    supported from Power7.  Actually implementation of "fctiw" only needs
    stfiwx which is supported by the old 32-bit processors.  This patch
    enables "fctiw" expand for these processors.
    
    gcc/
            PR target/112707
            * config/rs6000/rs6000.md (expand lrint<mode>si2): New.
            (insn lrint<mode>si2): Rename to...
            (*lrint<mode>si): ...this.
            (lrint<mode>si_di): New.
    
    gcc/testsuite/
            PR target/112707
            * gcc.target/powerpc/pr112707-1.c: New.

Diff:
---
 gcc/config/rs6000/rs6000.md                   | 30 ++++++++++++++++++++++++++-
 gcc/testsuite/gcc.target/powerpc/pr112707-1.c | 16 ++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 28482e3617e..3d9491769fc 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -6740,7 +6740,27 @@
   "fctid %0,%1"
   [(set_attr "type" "fp")])
 
-(define_insn "lrint<mode>si2"
+(define_expand "lrint<mode>si2"
+  [(set (match_operand:SI 0 "gpc_reg_operand" "=d")
+	(unspec:SI [(match_operand:SFDF 1 "gpc_reg_operand" "<rreg2>")]
+		   UNSPEC_FCTIW))]
+  "TARGET_HARD_FLOAT && TARGET_STFIWX"
+{
+  /* For those old archs in which SImode can't be hold in float registers,
+     call lrint<mode>si_di to put the result in DImode then convert it via
+     stack.  */
+  if (!TARGET_POPCNTD)
+    {
+      rtx tmp = gen_reg_rtx (DImode);
+      emit_insn (gen_lrint<mode>si_di (tmp, operands[1]));
+      rtx stack = rs6000_allocate_stack_temp (SImode, false, true);
+      emit_insn (gen_stfiwx (stack, tmp));
+      emit_move_insn (operands[0], stack);
+      DONE;
+    }
+})
+
+(define_insn "*lrint<mode>si"
   [(set (match_operand:SI 0 "gpc_reg_operand" "=d")
 	(unspec:SI [(match_operand:SFDF 1 "gpc_reg_operand" "<rreg2>")]
 		   UNSPEC_FCTIW))]
@@ -6748,6 +6768,14 @@
   "fctiw %0,%1"
   [(set_attr "type" "fp")])
 
+(define_insn "lrint<mode>si_di"
+  [(set (match_operand:DI 0 "gpc_reg_operand" "=d")
+	(unspec:DI [(match_operand:SFDF 1 "gpc_reg_operand" "<rreg2>")]
+		   UNSPEC_FCTIW))]
+  "TARGET_HARD_FLOAT && !TARGET_POPCNTD"
+  "fctiw %0,%1"
+  [(set_attr "type" "fp")])
+
 (define_insn "btrunc<mode>2"
   [(set (match_operand:SFDF 0 "gpc_reg_operand" "=d,wa")
 	(unspec:SFDF [(match_operand:SFDF 1 "gpc_reg_operand" "d,wa")]
diff --git a/gcc/testsuite/gcc.target/powerpc/pr112707-1.c b/gcc/testsuite/gcc.target/powerpc/pr112707-1.c
new file mode 100644
index 00000000000..cce6bd7f690
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr112707-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mdejagnu-cpu=7450 -fno-math-errno" } */
+/* { dg-require-effective-target ilp32 } */
+/* { dg-skip-if "" { has_arch_ppc64 } } */
+/* { dg-final { scan-assembler-times {\mfctiw\M} 2 } }  */
+/* { dg-final { scan-assembler-times {\mstfiwx\M} 2 } }  */
+
+int test1 (double a)
+{
+  return __builtin_irint (a);
+}
+
+int test2 (float a)
+{
+  return __builtin_irint (a);
+}