[gcc r15-1167] [PATCH v1] Widening-Mul: Fix one ICE of gcall insertion for PHI match

[Jeff Law]

https://gcc.gnu.org/g:d03ff3fd3e2da1352a404e3c53fe61314569345c

commit r15-1167-gd03ff3fd3e2da1352a404e3c53fe61314569345c
Author: Pan Li <pan2.li@intel.com>
Date:   Mon Jun 10 14:13:38 2024 -0600

    [PATCH v1] Widening-Mul: Fix one ICE of gcall insertion for PHI match
    
    When enabled the PHI handing for COND_EXPR,  we need to insert the gcall
    to replace the PHI node.  Unfortunately,  I made a mistake that insert
    the gcall to before the last stmt of the bb.  See below gimple,  the PHI
    is located at no.1 but we insert the gcall (aka no.9) to the end of
    the bb.  Then the use of _9 in no.2 will have no def and will trigger
    ICE when verify_ssa.
    
      1. # _9 = PHI <_3(4), 18446744073709551615(3)> // The PHI node to be deleted.
      2. prephitmp_36 = (char *) _9;
      3. buf.write_base = string_13(D);
      4. buf.write_ptr = string_13(D);
      5. buf.write_end = prephitmp_36;
      6. buf.written = 0;
      7. buf.mode = 3;
      8. _7 = buf.write_end;
      9. _9 = .SAT_ADD (string.0_2, maxlen_15(D));   // Insert gcall to last bb by mistake
    
    This patch would like to insert the gcall to before the start of the bb
    stmt.  To ensure the possible use of PHI_result will have a def exists.
    After this patch the above gimple will be:
    
      0. _9 = .SAT_ADD (string.0_2, maxlen_15(D));   // Insert gcall to start bb by mistake
      1. # _9 = PHI <_3(4), 18446744073709551615(3)> // The PHI node to be deleted.
      2. prephitmp_36 = (char *) _9;
      3. buf.write_base = string_13(D);
      4. buf.write_ptr = string_13(D);
      5. buf.write_end = prephitmp_36;
      6. buf.written = 0;
      7. buf.mode = 3;
      8. _7 = buf.write_end;
    
    The below test suites are passed for this patch:
    * The rv64gcv fully regression test with newlib.
    * The rv64gcv build with glibc.
    * The x86 regression test with newlib.
    * The x86 bootstrap test with newlib.
    
            PR target/115387
    
    gcc/ChangeLog:
    
            * tree-ssa-math-opts.cc (math_opts_dom_walker::after_dom_children): Take
            the gsi of start_bb instead of last_bb.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/pr115387-1.c: New test.
            * gcc.target/riscv/pr115387-2.c: New test.

Diff:
---
 gcc/testsuite/gcc.target/riscv/pr115387-1.c | 35 +++++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/riscv/pr115387-2.c | 18 +++++++++++++++
 gcc/tree-ssa-math-opts.cc                   |  2 +-
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.target/riscv/pr115387-1.c b/gcc/testsuite/gcc.target/riscv/pr115387-1.c
new file mode 100644
index 00000000000..a1c926977c4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr115387-1.c
@@ -0,0 +1,35 @@
+/* Test there is no ICE when compile.  */
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
+
+#define PRINTF_CHK 0x34
+
+typedef unsigned long uintptr_t;
+
+struct __printf_buffer {
+  char *write_ptr;
+  int status;
+};
+
+extern void __printf_buffer_init_end (struct __printf_buffer *, char *, char *);
+
+void
+test (char *string, unsigned long maxlen, unsigned mode_flags)
+{
+  struct __printf_buffer buf;
+
+  if ((mode_flags & PRINTF_CHK) != 0)
+    {
+      string[0] = '\0';
+      uintptr_t end;
+
+      if (__builtin_add_overflow ((uintptr_t) string, maxlen, &end))
+	end = -1;
+
+      __printf_buffer_init_end (&buf, string, (char *) end);
+    }
+  else
+    __printf_buffer_init_end (&buf, string, (char *) ~(uintptr_t) 0);
+
+  *buf.write_ptr = '\0';
+}
diff --git a/gcc/testsuite/gcc.target/riscv/pr115387-2.c b/gcc/testsuite/gcc.target/riscv/pr115387-2.c
new file mode 100644
index 00000000000..7183bf18dfd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr115387-2.c
@@ -0,0 +1,18 @@
+/* Test there is no ICE when compile.  */
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
+
+#include <stddef.h>
+#include <stdint-gcc.h>
+
+char *
+test (char *string, size_t maxlen)
+{
+  string[0] = '\0';
+  uintptr_t end;
+
+  if (__builtin_add_overflow ((uintptr_t) string, maxlen, &end))
+    end = -1;
+
+  return (char *) end;
+}
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index 173b0366f5e..fbb8e0ea306 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -6102,7 +6102,7 @@ math_opts_dom_walker::after_dom_children (basic_block bb)
   for (gphi_iterator psi = gsi_start_phis (bb); !gsi_end_p (psi);
     gsi_next (&psi))
     {
-      gimple_stmt_iterator gsi = gsi_last_bb (bb);
+      gimple_stmt_iterator gsi = gsi_start_bb (bb);
       match_unsigned_saturation_add (&gsi, psi.phi ());
     }