[PATCH v3] arm.cc: fix thumb1 prologue high reg restore violates -ffixed-rX [PR117468]

[Matt Parks]

This patch fixes PR117468:
ARM thumb1 compilation using -ffixed-reg with r4-r7, without -Os (which
prohibits use of high registers), produces bad high register restoration
code that clobbers the fixed register.

gcc/ChangeLog:
        PR target/117468
        * arm.cc (thumb1_prologue_unused_call_clobbered_lo_regs): Take fixed 
regs into account.
        * arm.cc (thumb1_epilogue_unused_call_clobbered_lo_regs): Take fixed 
regs into account.


---
 gcc/config/arm/arm.cc                   |  6 ++++--
 gcc/testsuite/gcc.target/arm/pr117468.c | 13 +++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/arm/pr117468.c

diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index bde06f3fa86..de911981a5c 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -8274,7 +8274,8 @@ thumb1_prologue_unused_call_clobbered_lo_regs (void)
   bitmap prologue_live_out = df_get_live_out (ENTRY_BLOCK_PTR_FOR_FN (cfun));
 
   for (int reg = FIRST_LO_REGNUM; reg <= LAST_LO_REGNUM; reg++)
-    if (!callee_saved_reg_p (reg) && !REGNO_REG_SET_P (prologue_live_out, reg))
+    if (!callee_saved_reg_p (reg) && !REGNO_REG_SET_P (prologue_live_out, reg)
+        && !fixed_regs[reg])
       mask |= 1 << (reg - FIRST_LO_REGNUM);
   return mask;
 }
@@ -8287,7 +8288,8 @@ thumb1_epilogue_unused_call_clobbered_lo_regs (void)
   bitmap epilogue_live_in = df_get_live_in (EXIT_BLOCK_PTR_FOR_FN (cfun));
 
   for (int reg = FIRST_LO_REGNUM; reg <= LAST_LO_REGNUM; reg++)
-    if (!callee_saved_reg_p (reg) && !REGNO_REG_SET_P (epilogue_live_in, reg))
+    if (!callee_saved_reg_p (reg) && !REGNO_REG_SET_P (epilogue_live_in, reg)
+        && !fixed_regs[reg])
       mask |= 1 << (reg - FIRST_LO_REGNUM);
   return mask;
 }
diff --git a/gcc/testsuite/gcc.target/arm/pr117468.c 
b/gcc/testsuite/gcc.target/arm/pr117468.c
new file mode 100644
index 00000000000..dc2dd9720ec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr117468.c
@@ -0,0 +1,13 @@
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -ffixed-r7" } */
+/* { dg-require-effective-target arm_arch_v5t_thumb_ok } */
+/* { dg-add-options arm_arch_v5t_thumb } */
+void ext_func(int e1, int e2, int e3, int e4);
+
+int bad_func(int p1, int p2, int p3, int p4) {
+    ext_func(p4, p3, p2, p1);
+    return p1 + p2 + p3 + p4;
+}
+
+/* { dg-final { scan-assembler-not "pop.*r7" } } */
-- 
2.34.1