[gcc r9-10000] cplxlower: Avoid a transform when looking at a default definition

[gcc r9-10000] cplxlower: Avoid a transform when looking at a default definition

[Martin Jambor]

https://gcc.gnu.org/g:1dc4bed43760c4e291e072aa0c8c450f5775e25f

commit r9-10000-g1dc4bed43760c4e291e072aa0c8c450f5775e25f
Author: Martin Jambor <mjambor@suse.cz>
Date:   Wed Mar 30 13:47:24 2022 +0200

    cplxlower: Avoid a transform when looking at a default definition
    
    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.
    
    gcc/ChangeLog:
    
    2020-10-19  Martin Jambor  <mjambor@suse.cz>
    
            PR tree-optimization/97456
            PR middle-end/105071
            * tree-complex.c (set_component_ssa_name): Do not replace ignored decl
            default definitions with new component vars.  Reorder if conditions.
    
    gcc/testsuite/ChangeLog:
    
    2020-10-19  Martin Jambor  <mjambor@suse.cz>
    
            PR tree-optimization/97456
            * gcc.dg/tree-ssa/pr97456.c: New test.
    
    (cherry picked from commit 619f91eaa8c8a50f1f9d3e7b96ee837037f0e806)

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr97456.c | 40 +++++++++++++++++++++++++++++++++
 gcc/tree-complex.c                      |  3 ++-
 2 files changed, 42 insertions(+), 1 deletion(-)

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 d4b053d68e1..36a4d6f06d5 100644
--- a/gcc/tree-complex.c
+++ b/gcc/tree-complex.c
@@ -569,7 +569,8 @@ 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)
+      if (!SSA_NAME_IS_DEFAULT_DEF (value)
+	  && SSA_NAME_VAR (ssa_name)
 	  && (!SSA_NAME_VAR (value) || DECL_IGNORED_P (SSA_NAME_VAR (value)))
 	  && !DECL_IGNORED_P (SSA_NAME_VAR (ssa_name)))
 	{