Patchwork [ARM] Implement __builtin_trap

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Submitter Ian Bolton
Date Dec. 6, 2013, 3:54 p.m.
Message ID <000501cef29b$64588aa0$2d099fe0$@bolton@arm.com>
Download mbox | patch
Permalink /patch/298066/
State New
Headers show

Comments

Ian Bolton - Dec. 6, 2013, 3:54 p.m.
> > Hi,
> >
> > Currently, on ARM, you have to either call abort() or raise(SIGTRAP)
> > to achieve a handy crash.
> >
> > This patch allows you to instead call __builtin_trap() which is much
> > more efficient at falling over because it becomes just a single
> > instruction that will trap for you.
> >
> > Two testcases have been added (for ARM and Thumb) and both pass.
> >
> >
> > Note: This is a modified version of a patch originally submitted by
> Mark
> > Mitchell back in 2010, which came in response to PR target/59091.
> >
> > http://gcc.gnu.org/ml/gcc-patches/2010-09/msg00639.html
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59091
> >
> > The main update, other than cosmetic differences, is that we've
> chosen
> > the same ARM encoding as LLVM for practical purposes.  (The Thumb
> > encoding in Mark's patch already matched LLVM.)
> >
> >
> > OK for trunk?
> >
> > Cheers,
> > Ian
> >
> >
> > 2013-12-04  Ian Bolton  <ian.bolton@arm.com>
> >            Mark Mitchell  <mark@codesourcery.com>
> >
> > gcc/
> >    * config/arm/arm.md (trap): New pattern.
> >    * config/arm/types.md: Added a type for trap.
> >
> > testsuite/
> >    * gcc.target/arm/builtin-trap.c: New test.
> >    * gcc.target/arm/thumb-builtin-trap.c: Likewise.
> > <aarch32-builtin-trap-v2.txt>
> 
> This needs to set the conds attribute to "unconditional".  Otherwise
> the ARM backend might try to turn this into a conditional instruction.
> 
> R.

Thanks, Richard. I fixed it up, tested it and committed as trivial
difference compared to what was approved already.

Patch

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index dd73366..934b859 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -9927,6 +9927,23 @@ 
    (set_attr "type" "mov_reg")]
 )
 
+(define_insn "trap"
+  [(trap_if (const_int 1) (const_int 0))]
+  ""
+  "*
+  if (TARGET_ARM)
+    return \".inst\\t0xe7f000f0\";
+  else
+    return \".inst\\t0xdeff\";
+  "
+  [(set (attr "length")
+	(if_then_else (eq_attr "is_thumb" "yes")
+		      (const_int 2)
+		      (const_int 4)))
+   (set_attr "type" "trap")
+   (set_attr "conds" "unconditional")]
+)
+
 
 ;; Patterns to allow combination of arithmetic, cond code and shifts
 
diff --git a/gcc/config/arm/types.md b/gcc/config/arm/types.md
index 1c4b9e3..6351f08 100644
--- a/gcc/config/arm/types.md
+++ b/gcc/config/arm/types.md
@@ -152,6 +152,7 @@ 
 ; store2             store 2 words to memory from arm registers.
 ; store3             store 3 words to memory from arm registers.
 ; store4             store 4 (or more) words to memory from arm registers.
+; trap               cause a trap in the kernel.
 ; udiv               unsigned division.
 ; umaal              unsigned multiply accumulate accumulate long.
 ; umlal              unsigned multiply accumulate long.
@@ -645,6 +646,7 @@ 
   store2,\
   store3,\
   store4,\
+  trap,\
   udiv,\
   umaal,\
   umlal,\
diff --git a/gcc/testsuite/gcc.target/arm/builtin-trap.c b/gcc/testsuite/gcc.target/arm/builtin-trap.c
new file mode 100644
index 0000000..4ff8d25
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/builtin-trap.c
@@ -0,0 +1,10 @@ 
+/* { dg-do compile } */
+/* { dg-require-effective-target arm32 } */
+
+void
+trap ()
+{
+  __builtin_trap ();
+}
+
+/* { dg-final { scan-assembler "0xe7f000f0" { target { arm_nothumb } } } } */
diff --git a/gcc/testsuite/gcc.target/arm/thumb-builtin-trap.c b/gcc/testsuite/gcc.target/arm/thumb-builtin-trap.c
new file mode 100644
index 0000000..22e90e7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/thumb-builtin-trap.c
@@ -0,0 +1,11 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mthumb" } */
+/* { dg-require-effective-target arm_thumb1_ok } */
+
+void
+trap ()
+{
+  __builtin_trap ();
+}
+
+/* { dg-final { scan-assembler "0xdeff" } } */