[Bug target/79430] [7/8 Regression] action of statement incorrectly optimised away

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79430

--- Comment #80 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The only difference with the #c79 patch on the testcase is:
@@ -18865,7 +18865,6 @@ __shower_core_MOD_shower_generate_next_i
        call    integral_over_z_part_isr.6797
 .LVL1471:
 .LM2026:
-       fldt    64(%rsp)
        fldt    496(%rsp)
        popq    %rsi
 .LCFI707:
@@ -18873,6 +18872,8 @@ __shower_core_MOD_shower_generate_next_i
 .LCFI708:
        movq    80(%rsp), %rax
        movq    96(%rsp), %r11
+       fldt    64(%rsp)
+       fxch    %st(1)
        fucomi  %st(1), %st
        fstp    %st(1)
        fldt    112(%rsp)