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[committed,PR,rtl-optimization/116437] Fix RTL checking issue in ext-dce

Message ID f325f8e6-4c4e-4625-9c35-9834ff33148f@gmail.com
State New
Headers show
Series [committed,PR,rtl-optimization/116437] Fix RTL checking issue in ext-dce | expand

Commit Message

Jeff Law Aug. 21, 2024, 10:54 p.m. UTC 
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.

Jeff
commit cdc9cd4afe8949276a0c50215eb7f23e2086044f
Author: Jeff Law <jlaw@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.
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Patch

diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index eee9208f0d6..35c06469b82 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)
 	{