Darwin, Arm64 : Truncate char immediates in vector initializers to mo…

…de size.

Darwin has signed chars, so that 8b immediates > 127 appear to be negative
which produce large positive (out of assembler range) values when inspected
by UINTVAL ().  This patch truncates the values to the bitrange of the mode
of the input.

Fixes github issue 15.

gcc/config/aarch64/aarch64.c

@@ -20406,6 +20406,16 @@ aarch64_output_simd_mov_immediate (rtx const_vector, unsigned width,
     }
 
   gcc_assert (CONST_INT_P (info.u.mov.value));
+  unsigned HOST_WIDE_INT value = UINTVAL (info.u.mov.value);
+
+  /* We have signed chars which can result in a sign-extended 8bit value
+     which is then emitted as an unsigned hex value, and the LLVM back end
+     assembler rejects that as being too big.  */
+  if (TARGET_MACHO && (known_eq (GET_MODE_BITSIZE (info.elt_mode), 8)))
+    {
+      unsigned HOST_WIDE_INT mask = (1U << GET_MODE_BITSIZE (info.elt_mode))-1;
+      value &= mask;
+    }
 
   if (which == AARCH64_CHECK_MOV)
     {
@@ -20414,16 +20424,16 @@ aarch64_output_simd_mov_immediate (rtx const_vector, unsigned width,
 		  ? "msl" : "lsl");
       if (lane_count == 1)
 	snprintf (templ, sizeof (templ), "%s\t%%d0, " HOST_WIDE_INT_PRINT_HEX,
-		  mnemonic, UINTVAL (info.u.mov.value));
+		  mnemonic, value);
       else if (info.u.mov.shift)
 	snprintf (templ, sizeof (templ), "%s\t%%0.%d%c, "
 		  HOST_WIDE_INT_PRINT_HEX ", %s %d", mnemonic, lane_count,
-		  element_char, UINTVAL (info.u.mov.value), shift_op,
+		  element_char, value, shift_op,
 		  info.u.mov.shift);
       else
 	snprintf (templ, sizeof (templ), "%s\t%%0.%d%c, "
 		  HOST_WIDE_INT_PRINT_HEX, mnemonic, lane_count,
-		  element_char, UINTVAL (info.u.mov.value));
+		  element_char, value);
     }
   else
     {
@@ -20432,12 +20442,12 @@ aarch64_output_simd_mov_immediate (rtx const_vector, unsigned width,
       if (info.u.mov.shift)
 	snprintf (templ, sizeof (templ), "%s\t%%0.%d%c, #"
 		  HOST_WIDE_INT_PRINT_DEC ", %s #%d", mnemonic, lane_count,
-		  element_char, UINTVAL (info.u.mov.value), "lsl",
+		  element_char, value, "lsl",
 		  info.u.mov.shift);
       else
 	snprintf (templ, sizeof (templ), "%s\t%%0.%d%c, #"
 		  HOST_WIDE_INT_PRINT_DEC, mnemonic, lane_count,
-		  element_char, UINTVAL (info.u.mov.value));
+		  element_char, value);
     }
   return templ;
 }