diff -ruNb gcc-10.1.0.orig/gcc/config/i386/host-mingw32.c gcc-10.1.0/gcc/config/i386/host-mingw32.c
--- gcc-10.1.0.orig/gcc/config/i386/host-mingw32.c	2020-05-07 12:49:59.000000000 +0200
+++ gcc-10.1.0/gcc/config/i386/host-mingw32.c	2020-05-19 23:31:44.749865244 +0200
@@ -44,9 +44,6 @@
 
 static inline void w32_error(const char*, const char*, int, const char*);
 
-/* FIXME: Is this big enough?  */
-static const size_t pch_VA_max_size  = 128 * 1024 * 1024;
-
 /* Granularity for reserving address space.  */
 static size_t va_granularity = 0x10000;
 
@@ -88,9 +85,6 @@
 mingw32_gt_pch_get_address (size_t size, int)
 {
   void* res;
-  size = (size + va_granularity - 1) & ~(va_granularity - 1);
-  if (size > pch_VA_max_size)
-    return NULL;
 
   /* FIXME: We let system determine base by setting first arg to NULL.
      Allocating at top of available address space avoids unnecessary
@@ -100,7 +94,7 @@
      If we allocate at bottom we need to reserve the address as early
      as possible and at the same point in each invocation. */
  
-  res = VirtualAlloc (NULL, pch_VA_max_size,
+  res = VirtualAlloc (NULL, size,
 		      MEM_RESERVE | MEM_TOP_DOWN,
 		      PAGE_NOACCESS);
   if (!res)
@@ -150,7 +144,7 @@
 
   /* Offset must be also be a multiple of allocation granularity for
      this to work.  We can't change the offset. */ 
-  if ((offset & (va_granularity - 1)) != 0 || size > pch_VA_max_size)
+  if ((offset & (va_granularity - 1)) != 0)
     return -1;
 
 
diff -ruNb gcc-10.1.0.orig/gcc/ggc-common.c gcc-10.1.0/gcc/ggc-common.c
--- gcc-10.1.0.orig/gcc/ggc-common.c	2020-05-07 12:49:59.000000000 +0200
+++ gcc-10.1.0/gcc/ggc-common.c	2020-05-19 23:39:22.033605708 +0200
@@ -591,6 +591,8 @@
   size_t i;
   struct mmap_info mmi;
   int result;
+  long pch_tabs_off;
+  long pch_data_off;
 
   /* Delete any deletable objects.  This makes ggc_pch_read much
      faster, as it can be sure that no GCable objects remain other
@@ -600,19 +602,25 @@
       memset (rti->base, 0, rti->stride);
 
   /* Read in all the scalar variables.  */
+  /* We need to read tables after mapping, or fatal_error will
+     segfault when gt_pch_use_address returns -1. Skip them for now. */
+  pch_tabs_off = ftell(f);
+
+  /* Skip all the scalar variables. */
   for (rt = gt_pch_scalar_rtab; *rt; rt++)
     for (rti = *rt; rti->base != NULL; rti++)
-      if (fread (rti->base, rti->stride, 1, f) != 1)
-	fatal_error (input_location, "cannot read PCH file: %m");
+      if (fseek (f, rti->stride, SEEK_CUR) != 0)
+        fatal_error (input_location, "can%'t read PCH file: %m");
 
   /* Read in all the global pointers, in 6 easy loops.  */
+  /* Skip all the global pointers. */
   for (rt = gt_ggc_rtab; *rt; rt++)
     for (rti = *rt; rti->base != NULL; rti++)
       for (i = 0; i < rti->nelt; i++)
-	if (fread ((char *)rti->base + rti->stride * i,
-		   sizeof (void *), 1, f) != 1)
-	  fatal_error (input_location, "cannot read PCH file: %m");
+        if (fseek (f, sizeof (void *), SEEK_CUR) != 0)
+          fatal_error (input_location, "can%'t read PCH file: %m");
 
+  /* mmi still has to be read now. */
   if (fread (&mmi, sizeof (mmi), 1, f) != 1)
     fatal_error (input_location, "cannot read PCH file: %m");
 
@@ -624,11 +632,35 @@
     {
       if (fseek (f, mmi.offset, SEEK_SET) != 0
 	  || fread (mmi.preferred_base, mmi.size, 1, f) != 1)
-	fatal_error (input_location, "cannot read PCH file: %m");
+        fatal_error (input_location, "can%'t read PCH file: %m");
+
     }
   else if (fseek (f, mmi.offset + mmi.size, SEEK_SET) != 0)
     fatal_error (input_location, "cannot read PCH file: %m");
 
+  /* File mapping done, read tables now. */
+  pch_data_off = ftell(f);
+  
+  if (fseek (f, pch_tabs_off, SEEK_SET) != 0)
+    fatal_error (input_location, "can%'t read PCH file: %m");
+ 
+  /* Read in all the scalar variables.  */
+  for (rt = gt_pch_scalar_rtab; *rt; rt++)
+    for (rti = *rt; rti->base != NULL; rti++)
+      if (fread (rti->base, rti->stride, 1, f) != 1)
+        fatal_error (input_location, "can%'t read PCH file: %m");
+
+  /* Read in all the global pointers, in 6 easy loops.  */
+  for (rt = gt_ggc_rtab; *rt; rt++)
+    for (rti = *rt; rti->base != NULL; rti++)
+      for (i = 0; i < rti->nelt; i++)
+        if (fread ((char *)rti->base + rti->stride * i,
+            sizeof (void *), 1, f) != 1)
+          fatal_error (input_location, "can%'t read PCH file: %m");
+
+  if (fseek (f, pch_data_off, SEEK_SET) != 0)
+    fatal_error (input_location, "can%'t read PCH file: %m");
+
   ggc_pch_read (f, mmi.preferred_base);
 
   gt_pch_restore_stringpool ();