[gcc r12-8627] Fix tree-opt/PR106087: ICE with inline-asm with multiple output and assigned only static vars

[Richard Biener]

https://gcc.gnu.org/g:e0e388998b797da09a8c018f6f94d1358fd4b8f1

commit r12-8627-ge0e388998b797da09a8c018f6f94d1358fd4b8f1
Author: Andrew Pinski <apinski@marvell.com>
Date:   Thu Jul 7 22:06:19 2022 +0000

    Fix tree-opt/PR106087: ICE with inline-asm with multiple output and assigned only static vars
    
    The problem here is that when we mark the ssa name that was referenced in the now removed
    dead store (to a write only static variable), the inline-asm would also be removed
    even though it was defining another ssa name. This fixes the problem by checking
    to make sure that the statement was only defining one ssa name.
    
    Committed as approved after a bootstrapped and tested on x86_64 with no regressions.
    
            PR tree-optimization/106087
    
    gcc/ChangeLog:
    
            * tree-ssa-dce.cc (simple_dce_from_worklist): Check
            to make sure the statement is only defining one operand.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.c-torture/compile/inline-asm-1.c: New test.
    
    (cherry picked from commit 71e3daa31cfa35ee58e5899cb00767be92227fd2)

Diff:
---
 gcc/testsuite/gcc.c-torture/compile/inline-asm-1.c | 14 ++++++++++++++
 gcc/tree-ssa-dce.cc                                |  7 +++++++
 2 files changed, 21 insertions(+)

diff --git a/gcc/testsuite/gcc.c-torture/compile/inline-asm-1.c b/gcc/testsuite/gcc.c-torture/compile/inline-asm-1.c
new file mode 100644
index 00000000000..0044cb761b6
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/inline-asm-1.c
@@ -0,0 +1,14 @@
+/* PR tree-opt/106087,
+   simple_dce_from_worklist would delete the
+   inline-asm when it was still being referenced
+   by the other ssa name. */
+
+static int t;
+
+int f(void)
+{
+  int tt, tt1;
+  asm("":"=r"(tt), "=r"(tt1));
+  t = tt1;
+  return tt;
+}
diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index 2067b711d5b..4b7b664867d 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -2060,6 +2060,13 @@ simple_dce_from_worklist (bitmap worklist)
       if (gimple_has_side_effects (t))
 	continue;
 
+      /* The defining statement needs to be defining only this name.
+	 ASM is the only statement that can define more than one
+	 (non-virtual) name. */
+      if (is_a<gasm *>(t)
+	  && !single_ssa_def_operand (t, SSA_OP_DEF))
+	continue;
+
       /* Don't remove statements that are needed for non-call
 	 eh to work.  */
       if (stmt_unremovable_because_of_non_call_eh_p (cfun, t))