[PATCH] cplxlower: Avoid a transform when looking at a default definition

[Martin Jambor]

Hi,

in PR 97456, IPA-SRA triggers a bug in tree-complex.c where it
converts:

 <bb 2>
   a$_M_value_21 = COMPLEX_EXPR <ISRA.18_10(D), ISRA.18_10(D)>;

(where ISRA.18 is IPA-SRA created PARM_DECL with DECL_IGNORED_P set,
which is why it only happens with IPA-SRA) into:

  <bb 2>
    a$_M_value_21 = COMPLEX_EXPR <a$_M_value$real_10(D), a$_M_value$real_10(D)>;

i.e. it replaces two uses of the parameter default-def with two
uninitialized default-defs of a new variable - all in hope to produce
code with better debug info.

This patch fixes it by avoiding the transform when the SSA_NAME to be
replaced is a default definition.  Bootstrapped and tested on
x86_64-linux.  OK for trunk and the gcc-10 branch?

Thanks,

Martin


gcc/ChangeLog:

2020-10-16  Martin Jambor  <mjam...@suse.cz>

        PR tree-optimization/97456
        * tree-complex.c (set_component_ssa_name): Do not replace ignored decl
        default definitions with new component vars.  Reorder if conditions.

gcc/testsuite/ChangeLog:

2020-10-16  Martin Jambor  <mjam...@suse.cz>

        PR tree-optimization/97456
        * gcc.dg/tree-ssa/pr97456.c: New test.
---
 gcc/testsuite/gcc.dg/tree-ssa/pr97456.c | 40 +++++++++++++++++++++++++
 gcc/tree-complex.c                      |  6 ++--
 2 files changed, 44 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr97456.c

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr97456.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr97456.c
new file mode 100644
index 00000000000..5171c9b4577
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr97456.c
@@ -0,0 +1,40 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fwhole-program" } */
+
+
+float val2 = 1.710780f;
+float val3;
+volatile float vf;
+
+int __attribute__((noipa))
+get_bool (void)
+{
+  return 1;
+}
+
+int __attribute__((noinline))
+wrong (float *pos)
+{
+  _Complex float a;
+
+  __real__ a = *pos;
+  __imag__ a = *pos;
+
+  _Complex float b = 0 + 0i;
+
+  b = b + a;
+
+  if (b == 0.0f)
+    return 1;
+
+  vf = __imag__ b;
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  float val = get_bool () == 1 ? val2 : val3;
+
+  if ((wrong(&val), wrong(&val)))
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-complex.c b/gcc/tree-complex.c
index 2e54bbb917c..71ad7c18523 100644
--- a/gcc/tree-complex.c
+++ b/gcc/tree-complex.c
@@ -570,8 +570,10 @@ set_component_ssa_name (tree ssa_name, bool imag_p, tree 
value)
       /* Replace an anonymous base value with the variable from cvc_lookup.
         This should result in better debug info.  */
       if (SSA_NAME_VAR (ssa_name)
-         && (!SSA_NAME_VAR (value) || DECL_IGNORED_P (SSA_NAME_VAR (value)))
-         && !DECL_IGNORED_P (SSA_NAME_VAR (ssa_name)))
+         && !DECL_IGNORED_P (SSA_NAME_VAR (ssa_name))
+         && (!SSA_NAME_VAR (value)
+             || (DECL_IGNORED_P (SSA_NAME_VAR (value))
+                 && !SSA_NAME_IS_DEFAULT_DEF (value))))
        {
          comp = get_component_var (SSA_NAME_VAR (ssa_name), imag_p);
          replace_ssa_name_symbol (value, comp);
-- 
2.28.0