Revert g-465c7c89

The patch caused regressions in gcc.target/sh/pr64345-1.c on
sh3-linux-gnu and gcc.target/m68k/pr39726.c on m68k-linux-gnu.
It didn't look like they would be fixable in an acceptably
non-invasive and unhacky way, so punting till future releases.

2020-01-29  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	Revert:

	2020-01-28  Richard Sandiford  <richard.sandiford@arm.com>

	PR rtl-optimization/87763
	* simplify-rtx.c (simplify_truncation): Extend sign/zero_extract
	simplification to handle subregs as well as bare regs.
	* config/i386/i386.md (*testqi_ext_3): Match QI extracts too.

gcc/ChangeLog

+2020-01-29  Richard Sandiford  <richard.sandiford@arm.com>
+
+	Revert:
+
+	2020-01-28  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR rtl-optimization/87763
+	* simplify-rtx.c (simplify_truncation): Extend sign/zero_extract
+	simplification to handle subregs as well as bare regs.
+	* config/i386/i386.md (*testqi_ext_3): Match QI extracts too.
+
 2020-01-29  Joel Hutton  <Joel.Hutton@arm.com>
 
 	PR target/93221

gcc/config/i386/i386.md

@@ -8925,7 +8925,7 @@
 (define_insn_and_split "*testqi_ext_3"
   [(set (match_operand 0 "flags_reg_operand")
         (match_operator 1 "compare_operator"
-	  [(zero_extract:SWI
+	  [(zero_extract:SWI248
 	     (match_operand 2 "nonimmediate_operand" "rm")
 	     (match_operand 3 "const_int_operand" "n")
 	     (match_operand 4 "const_int_operand" "n"))

gcc/simplify-rtx.c

@@ -736,9 +736,7 @@ simplify_truncation (machine_mode mode, rtx op,
      (*_extract:M1 (truncate:M1 (reg:M2)) (len) (pos')) if possible without
      changing len.  */
   if ((GET_CODE (op) == ZERO_EXTRACT || GET_CODE (op) == SIGN_EXTRACT)
-      && (REG_P (XEXP (op, 0))
-	  || (SUBREG_P (XEXP (op, 0))
-	      && REG_P (SUBREG_REG (XEXP (op, 0)))))
+      && REG_P (XEXP (op, 0))
       && GET_MODE (XEXP (op, 0)) == GET_MODE (op)
       && CONST_INT_P (XEXP (op, 1))
       && CONST_INT_P (XEXP (op, 2)))