From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 14 Feb 2020 13:03:19 +0000 (+0100)
Subject: x86: optimize away pointless segment overrides
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=92334ad2c6ad3aef4f78894c4d0f2794255317b3;p=binutils-gdb.git

x86: optimize away pointless segment overrides

When optimizing there's no point keeping the segment overrides when we
warn about their presence in the first place.
---

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 4f1aeed7c7c..0cbd2a5bbff 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,4 +1,11 @@
-2020-02-XX  Jan Beulich  <jbeulich@suse.com>
+2020-02-14  Jan Beulich  <jbeulich@suse.com>
+
+	* config/tc-i386.c (process_operands): Drop ineffectual segment
+	overrides when optimizing.
+	* testsuite/gas/i386/lea-optimize.d: New.
+	* testsuite/gas/i386/i386.exp: Run new test.
+
+2020-02-14  Jan Beulich  <jbeulich@suse.com>
 
 	* config/tc-i386.c (process_operands): Also check insn prefix
 	for ineffectual segment override warning. Don't cover possible
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 05151f2a636..d7d45de76e0 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -7165,10 +7165,17 @@ duplicate:
     }
 
   if ((i.seg[0] || i.prefix[SEG_PREFIX])
-      && !quiet_warnings
       && i.tm.base_opcode == 0x8d /* lea */
       && !is_any_vex_encoding(&i.tm))
-    as_warn (_("segment override on `%s' is ineffectual"), i.tm.name);
+    {
+      if (!quiet_warnings)
+	as_warn (_("segment override on `%s' is ineffectual"), i.tm.name);
+      if (optimize)
+	{
+	  i.seg[0] = NULL;
+	  i.prefix[SEG_PREFIX] = 0;
+	}
+    }
 
   /* If a segment was explicitly specified, and the specified segment
      is not the default, use an opcode prefix to select it.  If we
diff --git a/gas/testsuite/gas/i386/i386.exp b/gas/testsuite/gas/i386/i386.exp
index 147297e22f2..258fb763360 100644
--- a/gas/testsuite/gas/i386/i386.exp
+++ b/gas/testsuite/gas/i386/i386.exp
@@ -502,6 +502,7 @@ if [expr ([istarget "i*86-*-*"] ||  [istarget "x86_64-*-*"]) && [gas_32_check]]
     run_list_test "optimize-6a" "-I${srcdir}/$subdir -march=+noavx -al"
     run_dump_test "optimize-6b"
     run_list_test "optimize-7" "-I${srcdir}/$subdir -march=+noavx2 -al"
+    run_dump_test "lea-optimize"
     run_dump_test "align-branch-1a"
     run_dump_test "align-branch-1b"
     run_dump_test "align-branch-1c"
diff --git a/gas/testsuite/gas/i386/lea-optimize.d b/gas/testsuite/gas/i386/lea-optimize.d
new file mode 100644
index 00000000000..16e5b82daea
--- /dev/null
+++ b/gas/testsuite/gas/i386/lea-optimize.d
@@ -0,0 +1,13 @@
+#as: -O -q
+#objdump: -dw
+#name: i386 LEA-like segment overrride dropping
+#source: lea.s
+
+.*: +file format .*
+
+Disassembly of section .text:
+
+0+ <start>:
+[ 	]*[0-9a-f]+:[ 	]+8d 00[ 	]+lea[ 	]+\(%eax\),%eax
+[ 	]*[0-9a-f]+:[ 	]+8d 00[ 	]+lea[ 	]+\(%eax\),%eax
+#pass