[gcc r12-5853] [PR103097] tolerate reg-stack cross-block malformed asms

[gcc r12-5853] [PR103097] tolerate reg-stack cross-block malformed asms

[Alexandre Oliva]

https://gcc.gnu.org/g:af93386ffc18ca6c7d1949751ff97cc6ce092b2c

commit r12-5853-gaf93386ffc18ca6c7d1949751ff97cc6ce092b2c
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Dec 8 23:37:15 2021 -0300

    [PR103097] tolerate reg-stack cross-block malformed asms
    
    The testcase shows malformed asms in one block confuse reg-stack logic
    in another block.  Moving the resetting of any_malformed_asm to the
    end of the pass enables it to take effect throughout the affected
    function.
    
    
    for  gcc/ChangeLog
    
            PR target/103097
            * reg-stack.c (convert_regs_1): Move any_malformed_asm
            resetting...
            (reg_to_stack): ... here.
    
    for  gcc/testsuite/ChangeLog
    
            PR target/103097
            * gcc.target/i386/pr103097.c: New.

Diff:
---
 gcc/reg-stack.c                          |  5 ++---
 gcc/testsuite/gcc.target/i386/pr103097.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/gcc/reg-stack.c b/gcc/reg-stack.c
index 1d9ea035cf4..cc369f0b635 100644
--- a/gcc/reg-stack.c
+++ b/gcc/reg-stack.c
@@ -453,7 +453,7 @@ get_true_reg (rtx *pat)
       }
 }
 \f
-/* Set if we find any malformed asms in a block.  */
+/* Set if we find any malformed asms in a function.  */
 static bool any_malformed_asm;
 
 /* There are many rules that an asm statement for stack-like regs must
@@ -3014,8 +3014,6 @@ convert_regs_1 (basic_block block)
   bool cfg_altered = false;
   int debug_insns_with_starting_stack = 0;
 
-  any_malformed_asm = false;
-
   /* Choose an initial stack layout, if one hasn't already been chosen.  */
   if (bi->stack_in.top == -2)
     {
@@ -3385,6 +3383,7 @@ reg_to_stack (void)
 	  0, sizeof (char) * (max_uid + 1));
 
   convert_regs ();
+  any_malformed_asm = false;
 
   free_aux_for_blocks ();
   return true;
diff --git a/gcc/testsuite/gcc.target/i386/pr103097.c b/gcc/testsuite/gcc.target/i386/pr103097.c
new file mode 100644
index 00000000000..2b7a307deec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103097.c
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fharden-conditional-branches" } */
+
+/* This is a slightly simplified version of
+   gcc.target/s390/vector/long-double-asm-earlyclobber.c.  On x86, the f
+   constraints in asm statements imposes some requirements that the testcase
+   doesn't meet.  What's unusual is that -fharden-conditional-branches extends
+   the effects of the malformed asm onto a different basic blocks, which
+   reg-stack did not expect.  */
+
+#include <assert.h>
+#include <stdint.h>
+
+void
+f (void)
+{
+  long double res, x = 0;
+  asm("" : "=f"(res) /* { dg-error "must specify a single register" } */
+      : "0"(x));
+  assert (res == x);
+}  
+
+void
+g (void)
+{
+  long double res, x = 0;
+  asm("" : "=g"(res) /* this is ok.  */
+      : "0"(x));
+  assert (res == x);
+}