PR target/115751: Avoid force_reg in ix86_expand_ternlog.

This patch fixes a problem with splitting of complex AVX512 ternlog
instructions on x86_64.  A recent change allows the ternlog pattern
to have multiple mem-like operands prior to reload, by emitting any
"reloads" as necessary during split1, before register allocation.
The issue is that this code calls force_reg to place the mem-like
operand into a register, but unfortunately the vec_duplicate (broadcast)
form of operands supported by ternlog isn't considered a "general_operand",
i.e. supported by all instructions.  This mismatch triggers an ICE in
the middle-end's force_reg, even though the x86 supports loading these
vec_duplicate operands into a vector register in a single (move)
instruction.

This patch resolves this problem by replacing force_reg with calls
to gen_reg_rtx and emit_move (as the i386 backend, unlike the middle-end,
knows these will be recognized by recog).

2024-07-06  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR target/115751
	* config/i386/i386-expand.cc (ix86_expand_ternlog): Avoid use of
	force_reg to "reload" non-register operands, as these may contain
	vec_duplicate (broadcast) operands that aren't supported by
	force_reg.  Use (safer) gen_reg_rtx and emit_move instead.

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index a773b45bf03abffb18aa5cc65ef3e94eae25d4e5..bf79e59f811e23e3b43dd954bb46c86e745987c2 100644 (file)
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -26050,14 +26050,25 @@ ix86_expand_ternlog (machine_mode mode, rtx op0, rtx op1, rtx op2, int idx,
       break;
     }
 
-  tmp0 = register_operand (op0, mode) ? op0 : force_reg (mode, op0);
+  if (!register_operand (op0, mode))
+    {
+      /* We can't use force_reg (mode, op0).  */
+      tmp0 = gen_reg_rtx (GET_MODE (op0));
+      emit_move_insn (tmp0,op0);
+    }
+  else
+    tmp0 = op0;
   if (GET_MODE (tmp0) != mode)
     tmp0 = gen_lowpart (mode, tmp0);
 
   if (!op1 || rtx_equal_p (op0, op1))
     tmp1 = copy_rtx (tmp0);
   else if (!register_operand (op1, mode))
-    tmp1 = force_reg (mode, op1);
+    {
+      /* We can't use force_reg (mode, op1).  */
+      tmp1 = gen_reg_rtx (GET_MODE (op1));
+      emit_move_insn (tmp1, op1);
+    }
   else
     tmp1 = op1;
   if (GET_MODE (tmp1) != mode)