Re: Optimise away eh_frame advance_loc 0

[deliverable/binutils-gdb.git] / gas / dw2gencfi.c

diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index b01e4c4a9eda2e09008bd1683c851408258c21df..6c0478a72063801f1f91441a11350daa94605843 100644 (file)
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -1630,7 +1630,12 @@ output_cfi_insn (struct cfi_insn_data *insn)
            /* The code in ehopt.c expects that one byte of the encoding
               is already allocated to the frag.  This comes from the way
               that it scans the .eh_frame section looking first for the
-              .byte DW_CFA_advance_loc4.  */
+              .byte DW_CFA_advance_loc4.  Call frag_grow with the sum of
+              room needed by frag_more and frag_var to preallocate space
+              ensuring that the DW_CFA_advance_loc4 is in the fixed part
+              of the rs_cfa frag, so that the relax machinery can remove
+              the advance_loc should it advance by zero.  */
+           frag_grow (5);
            *frag_more (1) = DW_CFA_advance_loc4;
 
            frag_var (rs_cfa, 4, 0, DWARF2_LINE_MIN_INSN_LENGTH << 3,