As discussed recently, this patch adds the stack barriers that are
missing from MIPS' prologue and epilogue patterns. The attached
testcase failed before but passes afterwards.
Tested on mips64-linux-gnu and applied. Thanks to Jiangning
for highlighting the problem.
Richard
gcc/
* config/mips/mips.c (mips_frame_barrier): New function.
(mips_expand_prologue): Call it after allocating stack space.
(mips_deallocate_stack): New function.
(mips_expand_epilogue): Call mips_frame_barrier and
mips_deallocate_stack.
gcc/testsuite/
* gcc.target/mips/stack-1.c: New test.
Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c 2011-10-01 10:59:15.000000000 +0100
+++ gcc/config/mips/mips.c 2011-10-02 10:50:15.000000000 +0100
@@ -9892,6 +9892,14 @@ mips_output_function_epilogue (FILE *fil
mips_end_function_definition (fnname);
}
+/* Emit an optimisation barrier for accesses to the current frame. */
+
+static void
+mips_frame_barrier (void)
+{
+ emit_clobber (gen_frame_mem (BLKmode, stack_pointer_rtx));
+}
+
/* Save register REG to MEM. Make the instruction frame-related. */
static void
@@ -10035,6 +10043,7 @@ mips_expand_prologue (void)
insn = mips16e_build_save_restore (false, &mask, &offset,
nargs, step1);
RTX_FRAME_RELATED_P (emit_insn (insn)) = 1;
+ mips_frame_barrier ();
size -= step1;
/* Check if we need to save other registers. */
@@ -10075,6 +10084,7 @@ mips_expand_prologue (void)
insn = gen_add3_insn (stack_pointer_rtx, stack_pointer_rtx,
GEN_INT (-step1));
RTX_FRAME_RELATED_P (emit_insn (insn)) = 1;
+ mips_frame_barrier ();
size -= step1;
/* Start at the uppermost location for saving. */
@@ -10135,6 +10145,7 @@ mips_expand_prologue (void)
stack_pointer_rtx,
GEN_INT (-step1));
RTX_FRAME_RELATED_P (emit_insn (insn)) = 1;
+ mips_frame_barrier ();
size -= step1;
}
mips_for_each_saved_acc (size, mips_save_reg);
@@ -10175,6 +10186,7 @@ mips_expand_prologue (void)
(gen_rtx_SET (VOIDmode, stack_pointer_rtx,
plus_constant (stack_pointer_rtx, -size)));
}
+ mips_frame_barrier ();
}
/* Set up the frame pointer, if we're using one. */
@@ -10315,6 +10327,35 @@ mips_restore_reg (rtx reg, rtx mem)
mips_epilogue.cfa_restore_sp_offset);
}
+/* Emit code to set the stack pointer to BASE + OFFSET, given that
+ BASE + OFFSET is NEW_FRAME_SIZE bytes below the top of the frame.
+ BASE, if not the stack pointer, is available as a temporary. */
+
+static void
+mips_deallocate_stack (rtx base, rtx offset, HOST_WIDE_INT new_frame_size)
+{
+ if (base == stack_pointer_rtx && offset == const0_rtx)
+ return;
+
+ mips_frame_barrier ();
+ if (offset == const0_rtx)
+ {
+ emit_move_insn (stack_pointer_rtx, base);
+ mips_epilogue_set_cfa (stack_pointer_rtx, new_frame_size);
+ }
+ else if (TARGET_MIPS16 && base != stack_pointer_rtx)
+ {
+ emit_insn (gen_add3_insn (base, base, offset));
+ mips_epilogue_set_cfa (base, new_frame_size);
+ emit_move_insn (stack_pointer_rtx, base);
+ }
+ else
+ {
+ emit_insn (gen_add3_insn (stack_pointer_rtx, base, offset));
+ mips_epilogue_set_cfa (stack_pointer_rtx, new_frame_size);
+ }
+}
+
/* Emit any instructions needed before a return. */
void
@@ -10341,7 +10382,7 @@ mips_expand_epilogue (bool sibcall_p)
{
const struct mips_frame_info *frame;
HOST_WIDE_INT step1, step2;
- rtx base, target, insn;
+ rtx base, adjust, insn;
if (!sibcall_p && mips_can_use_return_insn ())
{
@@ -10384,31 +10425,14 @@ mips_expand_epilogue (bool sibcall_p)
step1 -= step2;
}
- /* Set TARGET to BASE + STEP1. */
- target = base;
- if (step1 > 0)
- {
- rtx adjust;
-
- /* Get an rtx for STEP1 that we can add to BASE. */
- adjust = GEN_INT (step1);
- if (!SMALL_OPERAND (step1))
- {
- mips_emit_move (MIPS_EPILOGUE_TEMP (Pmode), adjust);
- adjust = MIPS_EPILOGUE_TEMP (Pmode);
- }
-
- /* Normal mode code can copy the result straight into $sp. */
- if (!TARGET_MIPS16)
- target = stack_pointer_rtx;
-
- emit_insn (gen_add3_insn (target, base, adjust));
- mips_epilogue_set_cfa (target, step2);
+ /* Get an rtx for STEP1 that we can add to BASE. */
+ adjust = GEN_INT (step1);
+ if (!SMALL_OPERAND (step1))
+ {
+ mips_emit_move (MIPS_EPILOGUE_TEMP (Pmode), adjust);
+ adjust = MIPS_EPILOGUE_TEMP (Pmode);
}
-
- /* Copy TARGET into the stack pointer. */
- if (target != stack_pointer_rtx)
- mips_emit_move (stack_pointer_rtx, target);
+ mips_deallocate_stack (base, adjust, step2);
/* If we're using addressing macros, $gp is implicitly used by all
SYMBOL_REFs. We must emit a blockage insn before restoring $gp
@@ -10437,6 +10461,7 @@ mips_expand_epilogue (bool sibcall_p)
/* Restore the remaining registers and deallocate the final bit
of the frame. */
+ mips_frame_barrier ();
emit_insn (restore);
mips_epilogue_set_cfa (stack_pointer_rtx, 0);
}
@@ -10473,13 +10498,8 @@ mips_expand_epilogue (bool sibcall_p)
offset -= UNITS_PER_WORD;
/* If we don't use shoadow register set, we need to update SP. */
- if (!cfun->machine->use_shadow_register_set_p && step2 > 0)
- {
- emit_insn (gen_add3_insn (stack_pointer_rtx,
- stack_pointer_rtx,
- GEN_INT (step2)));
- mips_epilogue_set_cfa (stack_pointer_rtx, 0);
- }
+ if (!cfun->machine->use_shadow_register_set_p)
+ mips_deallocate_stack (stack_pointer_rtx, GEN_INT (step2), 0);
else
/* The choice of position is somewhat arbitrary in this case. */
mips_epilogue_emit_cfa_restores ();
@@ -10489,16 +10509,8 @@ mips_expand_epilogue (bool sibcall_p)
gen_rtx_REG (SImode, K0_REG_NUM)));
}
else
- {
- /* Deallocate the final bit of the frame. */
- if (step2 > 0)
- {
- emit_insn (gen_add3_insn (stack_pointer_rtx,
- stack_pointer_rtx,
- GEN_INT (step2)));
- mips_epilogue_set_cfa (stack_pointer_rtx, 0);
- }
- }
+ /* Deallocate the final bit of the frame. */
+ mips_deallocate_stack (stack_pointer_rtx, GEN_INT (step2), 0);
}
gcc_assert (!mips_epilogue.cfa_restores);
Index: gcc/testsuite/gcc.target/mips/stack-1.c
===================================================================
--- /dev/null 2011-10-02 10:31:49.966695399 +0100
+++ gcc/testsuite/gcc.target/mips/stack-1.c 2011-10-01 11:38:30.000000000
+0100
@@ -0,0 +1,11 @@
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler "addiu\t(\\\$sp,)?\\\$sp,\[1-9\]" } } */
+/* { dg-final { scan-assembler "\tlw\t" } } */
+/* { dg-final { scan-assembler-not "addiu\t(\\\$sp,)?\\\$sp,\[1-9\].*\tlw\t" }
} */
+
+int foo (int y)
+{
+ volatile int a = y;
+ volatile int *volatile b = &a;
+ return *b;
+}
