diff mbox series

[MIPS] Inhibit trailing .insn if pool is not followed by code

Message ID 20190603190739.147438-1-fshahbazker@wavecomp.com
State New
Headers show
Series [MIPS] Inhibit trailing .insn if pool is not followed by code | expand

Commit Message

Faraz Shahbazker June 3, 2019, 7:07 p.m. UTC 
The __pool and __pend symbols are used to mark the beginning and end of
inline constant pools in MIPS16 code regions.  However if the pool occurs
at the boundary of a code region and is not followed by further code,
presence of the __pend symbol can confuse the dissassembler in to treating
subsequent non-MIPS16 code block as MIPS16.

Based on original patch from Maciej W. Rozycki <macro@linux-mips.org>

gcc/
	* config/mips/mips.c (mips_final_postscan_insn): Only call
	`mips_set_text_contents_type' if a non-debug insn follows.

gcc/gcc/testsuite/
	* gcc.target/mips/data-sym-pool.c: Don't check for
	__pend symbol.
	* gcc.target/mips/data-sym-multi-pool.c: New test.
---
 gcc/config/mips/mips.c                             | 18 ++++++--
 .../gcc.target/mips/data-sym-multi-pool.c          | 51 ++++++++++++++++++++++
 gcc/testsuite/gcc.target/mips/data-sym-pool.c      |  7 +--
 3 files changed, 67 insertions(+), 9 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/mips/data-sym-multi-pool.c

Comments

Maciej W. Rozycki June 4, 2019, 9:07 p.m. UTC | #1 
On Mon, 3 Jun 2019, Faraz Shahbazker wrote:

> The __pool and __pend symbols are used to mark the beginning and end of
> inline constant pools in MIPS16 code regions.  However if the pool occurs
> at the boundary of a code region and is not followed by further code,
> presence of the __pend symbol can confuse the dissassembler in to treating
> subsequent non-MIPS16 code block as MIPS16.

 Thanks for looking into it.  FWIW I think the `__pend' symbol will best 
be still emitted for consistency, however as STT_OBJECT and consequently 
with no trailing `.insn'.

  Maciej
Jeff Law June 5, 2019, 10:34 p.m. UTC | #2 
On 6/4/19 3:07 PM, Maciej W. Rozycki wrote:
> On Mon, 3 Jun 2019, Faraz Shahbazker wrote:
> 
>> The __pool and __pend symbols are used to mark the beginning and end of
>> inline constant pools in MIPS16 code regions.  However if the pool occurs
>> at the boundary of a code region and is not followed by further code,
>> presence of the __pend symbol can confuse the dissassembler in to treating
>> subsequent non-MIPS16 code block as MIPS16.
> 
>  Thanks for looking into it.  FWIW I think the `__pend' symbol will best 
> be still emitted for consistency, however as STT_OBJECT and consequently 
> with no trailing `.insn'.
If I understand correctly we'd still want to call
mips_set_text_contents_type in all the cases we did before, but that
we'd pass in false for the FUNCTION_P argument?

jeff
Maciej W. Rozycki June 5, 2019, 10:48 p.m. UTC | #3 
On Wed, 5 Jun 2019, Jeff Law wrote:

> >  Thanks for looking into it.  FWIW I think the `__pend' symbol will best 
> > be still emitted for consistency, however as STT_OBJECT and consequently 
> > with no trailing `.insn'.
> If I understand correctly we'd still want to call
> mips_set_text_contents_type in all the cases we did before, but that
> we'd pass in false for the FUNCTION_P argument?

 Yes, I think it would be the most straightforward implementation.

  Maciej
diff mbox series

Patch

diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c
index c6433dc..3fb6c9d 100644
--- a/gcc/config/mips/mips.c
+++ b/gcc/config/mips/mips.c
@@ -20630,15 +20630,25 @@  static void
 mips_final_postscan_insn (FILE *file ATTRIBUTE_UNUSED, rtx_insn *insn,
 			  rtx *opvec, int noperands)
 {
+  rtx_insn *next_insn;
+
   if (mips_need_noat_wrapper_p (insn, opvec, noperands))
     mips_pop_asm_switch (&mips_noat);
 
   if (INSN_P (insn)
       && GET_CODE (PATTERN (insn)) == UNSPEC_VOLATILE
-      && XINT (PATTERN (insn), 1) == UNSPEC_CONSTTABLE_END)
-    mips_set_text_contents_type (asm_out_file, "__pend_",
-				 INTVAL (XVECEXP (PATTERN (insn), 0, 0)),
-				 TRUE);
+      && XINT (PATTERN (insn), 1) == UNSPEC_CONSTTABLE_END
+      && (next_insn = next_real_nondebug_insn (insn)))
+    {
+      /* Switch content type only if we know there is code beyond
+	 the constant pool.  */
+      if (INSN_P (next_insn)
+	  && (GET_CODE (PATTERN (next_insn)) != UNSPEC_VOLATILE
+	      || XINT (PATTERN (next_insn), 1) != UNSPEC_CONSTTABLE))
+	mips_set_text_contents_type (asm_out_file, "__pend_",
+				     INTVAL (XVECEXP (PATTERN (insn), 0, 0)),
+				     TRUE);
+    }
 }
 
 /* Return the function that is used to expand the <u>mulsidi3 pattern.
diff --git a/gcc/testsuite/gcc.target/mips/data-sym-multi-pool.c b/gcc/testsuite/gcc.target/mips/data-sym-multi-pool.c
new file mode 100644
index 0000000..2db90e3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/data-sym-multi-pool.c
@@ -0,0 +1,51 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mips16 -mcode-readable=yes" } */
+/* { dg-skip-if "per-function expected output" { *-*-* } { "-flto" } { "" } } */
+
+/* This testcase generates multiple constant pools within a function body.  */
+
+#define C(a,b) \
+  if (a > b)  goto gt; \
+  if (a < b)  goto lt;
+
+#define C4(x,b) C((x)[0], b) C((x)[1],b) C((x)[2],b) C((x)[3],b)
+#define C16(x,y) C4(x, (y)[0]) C4(x, (y)[1]) C4(x, (y)[2]) C4(x, (y)[3])
+
+#define C64(x,y) C16(x,y) C16(x+4,y) C16(x+8,y)
+#define C256(x,y) C64(x,y) C64(x,y+4) C64(x,y+8)
+
+unsigned foo(int x[64], int y[64])
+{
+  C256(x,y);
+
+  return 0x01234567;
+ gt:
+  return 0x12345678;
+ lt:
+  return 0xF0123456;
+}
+
+/*  Check that:
+1. The __pend symbol, when emitted is followed by an instruction:
+	.type	__pend_frob_<X>, @function	# Symbol # must match label.
+__pend_foo_<X>: 				# The symbol must match.
+	.insn
+.L<Y>:
+
+2. No __pend symbol is emitted for back-to-back pools, like
+
+__pend_foo_<X>:
+	.insn
+	.type	__pool_foo_<X>, @object
+
+3. No __pend symbol is emitted at the end of a function, like
+
+__pend_foo_<X>:
+	.insn
+	.end	foo
+
+  */
+
+/* { dg-final { scan-assembler "\t\\.type\t(__pend_foo_\[0-9\]+), @function\n\\1:\n\t\\.insn\n.L\[0-9\]+:\n" } }  */
+/* { dg-final { scan-assembler-not "__pend_foo_\[0-9\]+:\n\t\\.insn\n\t\\.type\t__pool_foo_\[0-9\]+, @object\n" } }  */
+/* { dg-final { scan-assembler-not "__pend_foo_\[0-9\]+:\n\t\\.insn\n\t\\.end\tfoo\n" } }  */
diff --git a/gcc/testsuite/gcc.target/mips/data-sym-pool.c b/gcc/testsuite/gcc.target/mips/data-sym-pool.c
index 8776d2b..8eac101 100644
--- a/gcc/testsuite/gcc.target/mips/data-sym-pool.c
+++ b/gcc/testsuite/gcc.target/mips/data-sym-pool.c
@@ -16,14 +16,11 @@  __pool_frob_3:					# The symbol must match.
 	.align	2
 $L3:						# The label must match.
 	.word	305419896
-	.type	__pend_frob_3, @function	# Symbol # must match label.
-__pend_frob_3:					# The symbol must match.
-	.insn
 
-   that is `__pool_*'/`__pend_*' symbols inserted around a constant pool.
+   that is `__pool_*' symbol is inserted before a constant pool.
 
    This code is built with `-mplt' to prevent the special `__gnu_local_gp'
    symbol from being placed in the constant pool at `-O0' for SVR4 code
    and consequently interfering with test expectations.  */
 
-/* { dg-final { scan-assembler "\tl\[wd\]\t\\\$\[0-9\]+,(.L(\[0-9\]+))\n.*\t\\.type\t(__pool_frob_\\2), @object\n\\3:\n\t\\.align\t2\n\\1:\n\t\\.d?word\t305419896\n\t\\.type\t(__pend_frob_\\2), @function\n\\4:\n\t\\.insn\n" } } */
+/* { dg-final { scan-assembler "\tlw\t\\\$\[0-9\]+,(.L(\[0-9\]+))\n.*\t\\.type\t(__pool_frob_\\2), @object\n\\3:\n\t\\.align\t2\n\\1:\n\t\\.word\t305419896\n" } } */