--- a/gcc/haifa-sched.c	2021-03-08 14:46:59.204000000 +0800
+++ b/gcc/haifa-sched.c	2021-03-09 13:32:40.656000000 +0800
@@ -2036,8 +2036,10 @@ model_start_update_pressure (struct mode
       /* The instruction wasn't part of the model schedule; it was moved
 	 from a different block.  Update the pressure for the end of
 	 the model schedule.  */
-      MODEL_REF_PRESSURE (group, point, pci) += delta;
-      MODEL_MAX_PRESSURE (group, point, pci) += delta;
+      if (MODEL_REF_PRESSURE (group, point, pci) != -1 || delta > 0)
+	MODEL_REF_PRESSURE (group, point, pci) += delta;
+      if (MODEL_MAX_PRESSURE (group, point, pci) != -1 || delta > 0)
+	MODEL_MAX_PRESSURE (group, point, pci) += delta;
     }
   else
     {
diff -uprN a/gcc/testsuite/gcc.dg/sche1-pressure-check.c b/gcc/testsuite/gcc.dg/sche1-pressure-check.c
--- a/gcc/testsuite/gcc.dg/sche1-pressure-check.c  1970-01-01 08:00:00.000000000 +0800
+++ b/gcc/testsuite/gcc.dg/sche1-pressure-check.c  2021-03-09 13:40:34.036000000 +0800
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+int a, g, h;
+char b, c;
+short d;
+static int e;
+int *volatile f;
+void i() {
+  int j = 0;
+  int *k = &a;
+  for (; c; c--) {
+    g && (d = 0);
+    j ^= 10;
+    {
+      int l[2];
+      l;
+      h = l[1];
+    }
+    e = 1;
+    for (; e <= 7; e++) {
+      *k = 6;
+      *f = b = 0;
+      for (; b <= 7; b++) {
+        int m = 5;
+        if (g)
+          *k &= m ^= j;
+      }
+    }
+  }
+}
+int main() {}
+