commit 68489d5729b4879bf2df540753fc7ea8ba1565a5
Author: Robin Dapp <rdapp@linux.ibm.com>
Date:   Mon Jan 24 10:28:05 2022 +0100

    ifcvt: Fix PR104153 and PR104198.
    
    This is a bugfix for aa8cfe785953a0e87d2472311e1260cd98c605c0 which
    broke an or1k test case (PR104153) as well as SPARC bootstrap (PR104198).
    
    cond_exec_get_condition () returns the jump condition directly and we now
    pass it to the backend.  The or1k backend modified the condition in-place
    (other backends do that as well) but this modification is not reverted
    when the sequence in question is discarded.  Therefore we copy the RTX
    instead of using it directly.
    
    The SPARC problem is due to the SPARC backend recreating the initial
    condition when being passed a CC comparison.  This causes the sequence
    to read from an already overwritten condition operand.  Generally, this
    could also happen on other targets.  The workaround is to always first
    emit to a temporary.  In a second run of noce_convert_multiple_1 we know
    which sequences actually require the comparison and will use no
    temporaries if all sequences after the current one do not require it.

diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index fe250d508e1..92c2b40a45a 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -3391,7 +3391,11 @@ noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
   rtx cond = noce_get_condition (jump, &cond_earliest, false);
 
   rtx cc_cmp = cond_exec_get_condition (jump);
+  if (cc_cmp)
+    cc_cmp = copy_rtx (cc_cmp);
   rtx rev_cc_cmp = cond_exec_get_condition (jump, /* get_reversed */ true);
+  if (rev_cc_cmp)
+    rev_cc_cmp = copy_rtx (rev_cc_cmp);
 
   rtx_insn *insn;
   int count = 0;
@@ -3515,6 +3519,7 @@ noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
       unsigned cost1 = 0, cost2 = 0;
       rtx_insn *seq, *seq1, *seq2;
       rtx temp_dest = NULL_RTX, temp_dest1 = NULL_RTX, temp_dest2 = NULL_RTX;
+      bool read_comparison = false;
 
       seq1 = try_emit_cmove_seq (if_info, temp, cond,
 				 new_val, old_val, need_cmov,
@@ -3524,10 +3529,38 @@ noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
 	 as well.  This allows the backend to emit a cmov directly without
 	 creating an additional compare for each.  If successful, costing
 	 is easier and this sequence is usually preferred.  */
-      seq2 = try_emit_cmove_seq (if_info, target, cond,
+      seq2 = try_emit_cmove_seq (if_info, temp, cond,
 				 new_val, old_val, need_cmov,
 				 &cost2, &temp_dest2, cc_cmp, rev_cc_cmp);
 
+      /* The backend might have created a sequence that uses the
+	 condition.  Check this.  */
+      rtx_insn *walk = seq2;
+      while (walk)
+	{
+	  rtx set = single_set (walk);
+
+	  if (!set || !SET_SRC (set)) {
+	      walk = NEXT_INSN (walk);
+	      continue;
+	  }
+
+	  rtx src = SET_SRC (set);
+
+	  if (XEXP (set, 1) && GET_CODE (XEXP (set, 1)) == IF_THEN_ELSE)
+	    ;
+	  else
+	    {
+	      if (reg_mentioned_p (XEXP (cond, 0), src)
+		  || reg_mentioned_p (XEXP (cond, 1), src))
+		{
+		  read_comparison = true;
+		  break;
+		}
+	    }
+	  walk = NEXT_INSN (walk);
+	}
+
       /* Check which version is less expensive.  */
       if (seq1 != NULL_RTX && (cost1 <= cost2 || seq2 == NULL_RTX))
 	{
@@ -3540,6 +3573,8 @@ noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
 	{
 	  seq = seq2;
 	  temp_dest = temp_dest2;
+	  if (!second_try && read_comparison)
+	    *last_needs_comparison = count;
 	}
       else
 	{
@@ -3558,6 +3593,12 @@ noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
       unmodified_insns->safe_push (insn);
     }
 
+  /* Even if we did not actually need the comparison, we want to make sure
+     to try a second time in order to get rid of the temporaries.  */
+  if (*last_needs_comparison == -1)
+    *last_needs_comparison = 0;
+
+
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.dg/pr104198.c b/gcc/testsuite/gcc.dg/pr104198.c
new file mode 100644
index 00000000000..bfc7a777184
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104198.c
@@ -0,0 +1,36 @@
+/* Make sure if conversion for two instructions does not break
+   anything (if it runs).  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -std=c99" } */
+
+#include <limits.h>
+#include <assert.h>
+
+__attribute__ ((noinline))
+int foo (int *a, int n)
+{
+  int min = 999999;
+  int bla = 0;
+  for (int i = 0; i < n; i++)
+    {
+      if (a[i] < min)
+	{
+	  min = a[i];
+	  bla = 1;
+	}
+    }
+
+  if (bla)
+    min += 1;
+  return min;
+}
+
+int main()
+{
+  int a[] = {2, 1, -13, INT_MAX, INT_MIN, 0};
+
+  int res = foo (a, sizeof (a) / sizeof (a[0]));
+
+  assert (res == (INT_MIN + 1));
+}