[gcc(refs/vendors/riscv/heads/gcc-14-with-riscv-opts)] [PR rtl-optimization/116437] Fix RTL checking issue in ext-dce

[Jeff Law via Gcc-cvs]

https://gcc.gnu.org/g:9660ade008244720fc3653865c7beaae09d6e3da

commit 9660ade008244720fc3653865c7beaae09d6e3da
Author: Jeff Law <j...@ventanamicro.com>
Date:   Wed Aug 21 16:52:23 2024 -0600

    [PR rtl-optimization/116437] Fix RTL checking issue in ext-dce
    
    Another RTL checking failure in ext-dce.  An easy one to fix this time.
    
    When we optimize an extension we have to go back and cleanup with
    SUBREG_PROMOTED state.  So we record the destination register into a bitmap 
as
    we make changes, then later do a single pass over the IL fixing any 
associated
    subreg expressions.
    
    The optimization is changing the SET_SRC and largely ignores the 
destination.
    The LHS could be a REG, SUBREG, or ZERO_EXTRACT.  If the LHS is a SUBREG or
    ZERO_EXTRACT we can just strip them.
    
    Bootstrapped and ran the testsuite with an RTL checking compiler and 
verified
    no ext-dce RTL checking failures tripped.  Also bootstrapped and regression
    tested x86_64 in the usual way.
    
    Pushing to the trunk.
    
            PR rtl-optimization/116437
    gcc/
            * ext-dce.cc (ext_dce_try_optimize_insn): Handle SUBREG and
            ZERO_EXTRACT destinations.
    
    (cherry picked from commit cdc9cd4afe8949276a0c50215eb7f23e2086044f)

Diff:
---
 gcc/ext-dce.cc | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index 60ae09e45dbf..0122b3a0d15b 100644
--- a/gcc/ext-dce.cc
+++ b/gcc/ext-dce.cc
@@ -422,8 +422,13 @@ ext_dce_try_optimize_insn (rtx_insn *insn, rtx set)
     {
       int ok = validate_change (insn, &SET_SRC (set), new_pattern, false);
 
+      rtx x = SET_DEST (set);
+      while (SUBREG_P (x) || GET_CODE (x) == ZERO_EXTRACT)
+       x = XEXP (x, 0);
+
+      gcc_assert (REG_P (x));
       if (ok)
-       bitmap_set_bit (changed_pseudos, REGNO (SET_DEST (set)));
+       bitmap_set_bit (changed_pseudos, REGNO (x));
 
       if (dump_file)
        {