Re: [ARM] Fix prologue and epilogue for interrupt function

[Jie Zhang <jie at codesourcery dot com>]

On 07/07/2010 09:49 PM, Paul Brook wrote:
> > ARM GCC will save r3 to the stack when it tries to align the stack to
> > double-word. But it can only do so when r3 will not be saved. Otherwise
> > there will be inconsistent information about how many registers will be
> > saved and how much the stack will be adjusted. This patch fixes it.
> >
> > Tested on arm-none-eabi. No regressions are found. Is it OK?
>
> Your test fails for Thumb multilibs.
>
> Other than that, ok.
Here is the updated patch, with test cases updated. The method used in 
the tests to make them work with thumb is Paul's idea. I will commit on 
trunk and 4.5 branch soon.


--
Jie Zhang
CodeSourcery

	* config/arm/arm.c (arm_get_frame_offsets): Don't use r3 to
	align the stack when it's going to be saved.

	testsuite/
	* gcc.target/arm/interrupt-1.c: New test.
	* gcc.target/arm/interrupt-2.c: New test.

Index: testsuite/gcc.target/arm/interrupt-1.c
===================================================================
--- testsuite/gcc.target/arm/interrupt-1.c	(revision 0)
+++ testsuite/gcc.target/arm/interrupt-1.c	(revision 0)
@@ -0,0 +1,23 @@
+/* Verify that prologue and epilogue are correct for functions with
+   __attribute__ ((interrupt)).  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+/* This test is not valid when -mthumb.  We just cheat.  */
+#ifndef __thumb__
+extern void bar (int);
+extern void foo (void) __attribute__ ((interrupt("IRQ")));
+
+void foo ()
+{
+  bar (0);
+}
+#else
+void foo ()
+{
+  asm ("stmfd\tsp!, {r0, r1, r2, r3, r4, fp, ip, lr}");
+  asm ("ldmfd\tsp!, {r0, r1, r2, r3, r4, fp, ip, pc}^");
+}
+#endif
+/* { dg-final { scan-assembler "stmfd\tsp!, {r0, r1, r2, r3, r4, fp, ip, lr}" } } */
+/* { dg-final { scan-assembler "ldmfd\tsp!, {r0, r1, r2, r3, r4, fp, ip, pc}\\^" } } */
Index: testsuite/gcc.target/arm/interrupt-2.c
===================================================================
--- testsuite/gcc.target/arm/interrupt-2.c	(revision 0)
+++ testsuite/gcc.target/arm/interrupt-2.c	(revision 0)
@@ -0,0 +1,26 @@
+/* Verify that prologue and epilogue are correct for functions with
+   __attribute__ ((interrupt)).  */
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+
+/* This test is not valid when -mthum.  We just cheat.  */
+#ifndef __thumb__
+extern void bar (int);
+extern void test (void) __attribute__((__interrupt__));
+
+int foo;
+void test()
+{
+  funcptrs(foo);
+  foo = 0;
+}
+#else
+void test ()
+{
+  asm ("stmfd\tsp!, {r0, r1, r2, r3, r4, r5, ip, lr}");
+  asm ("ldmfd\tsp!, {r0, r1, r2, r3, r4, r5, ip, pc}^");
+}
+#endif
+
+/* { dg-final { scan-assembler "stmfd\tsp!, {r0, r1, r2, r3, r4, r5, ip, lr}" } } */
+/* { dg-final { scan-assembler "ldmfd\tsp!, {r0, r1, r2, r3, r4, r5, ip, pc}\\^" } } */
Index: config/arm/arm.c
===================================================================
--- config/arm/arm.c	(revision 162071)
+++ config/arm/arm.c	(working copy)
@@ -14691,7 +14691,8 @@ arm_get_frame_offsets (void)
 	     generates better code on Thumb-2 by avoiding the need to
 	     use 32-bit push/pop instructions.  */
 	  if (!crtl->tail_call_emit
-	      && arm_size_return_regs () <= 12)
+	      && arm_size_return_regs () <= 12
+	      && (offsets->saved_regs_mask & (1 << 3)) == 0)
 	    {
 	      reg = 3;
 	    }