tree-optimization/100329 - avoid reassociating asm goto defs

This avoids reassociating asm goto defs because we have no idea
on which outgoing edge to insert defs.

2021-05-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100329
	* tree-ssa-reassoc.c (can_reassociate_p): Do not reassociate
	asm goto defs.
	(insert_stmt_after): Assert we're not running into asm goto.

	* gcc.dg/torture/pr100329.c: New testcase.

(cherry picked from commit a310bb73edc9548e08d1fa28e7a56246caf27757)

diff --git a/gcc/testsuite/gcc.dg/torture/pr100329.c b/gcc/testsuite/gcc.dg/torture/pr100329.c
new file mode 100644 (file)
index 0000000..b90700d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr100329.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-additional-options "--param tree-reassoc-width=2" } */
+
+unsigned int a0;
+
+unsigned int
+foo (unsigned int a1, unsigned int a2)
+{
+  unsigned int x;
+
+  asm goto ("" : "=r" (x) : : : lab);
+  a0 = x;
+
+ lab:
+  return x + a1 + a2 + 1;
+}

diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index 8e2a4896d14b79c7b34e5da0605990550278dd36..359367c9382c1c9ca4f61a937dafbffe92dacafe 100644 (file)
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -1446,6 +1446,10 @@ insert_stmt_after (gimple *stmt, gimple *insert_point)
       gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
       return;
     }
+  else if (gimple_code (insert_point) == GIMPLE_ASM)
+    /* We have no idea where to insert - it depends on where the
+       uses will be placed.  */
+    gcc_unreachable ();
   else
     /* We assume INSERT_POINT is a SSA_NAME_DEF_STMT of some SSA_NAME,
        thus if it must end a basic block, it should be a call that can
@@ -5893,6 +5897,12 @@ can_reassociate_p (tree op)
   tree type = TREE_TYPE (op);
   if (TREE_CODE (op) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op))
     return false;
+  /* Make sure asm goto outputs do not participate in reassociation since
+     we have no way to find an insertion place after asm goto.  */
+  if (TREE_CODE (op) == SSA_NAME
+      && gimple_code (SSA_NAME_DEF_STMT (op)) == GIMPLE_ASM
+      && gimple_asm_nlabels (as_a <gasm *> (SSA_NAME_DEF_STMT (op))) != 0)
+    return false;
   if ((ANY_INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_WRAPS (type))
       || NON_SAT_FIXED_POINT_TYPE_P (type)
       || (flag_associative_math && FLOAT_TYPE_P (type)))