Relax vector_builder::elt sanity check

I'd made it a precondition of vector_builder::elt that the encoding
must have been fully populated and that all implicit elements are
therefore defined.  But for one of the AArch64 patches I'm working on,
it'd be convenient to be able to look back at previous elements while
building up the encoding.  This patch therefore makes the assert
specific to implicit elements only.

2019-07-12  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* vector-builder.h (vector_builder::elt): Allow already-supplied
	elements to be read back before building is complete.

From-SVN: r273440

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7f01af33edbbb18bcd9889bf3240fe735d0f7ccc..43b52489921e4fe47c211d5d5dd3f915fd21cf6a 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2019-07-12  Richard Sandiford  <richard.sandiford@arm.com>
+
+       * vector-builder.h (vector_builder::elt): Allow already-supplied
+       elements to be read back before building is complete.
+
 2019-07-12  Eric Botcazou  <ebotcazou@adacore.com>
 
        PR rtl-optimization/91136

diff --git a/gcc/vector-builder.h b/gcc/vector-builder.h
index 9f95b01bc3b2ef233e3026a95c1de22bf13e903e..aac8a875a587126dc8fb1e92010793e8120ae704 100644 (file)
--- a/gcc/vector-builder.h
+++ b/gcc/vector-builder.h
@@ -199,14 +199,15 @@ template<typename T, typename Derived>
 T
 vector_builder<T, Derived>::elt (unsigned int i) const
 {
-  /* This only makes sense if the encoding has been fully populated.  */
-  gcc_checking_assert (encoded_nelts () <= this->length ());
-
   /* First handle elements that are already present in the underlying
      vector, regardless of whether they're part of the encoding or not.  */
   if (i < this->length ())
     return (*this)[i];
 
+  /* Extrapolation is only possible if the encoding has been fully
+     populated.  */
+  gcc_checking_assert (encoded_nelts () <= this->length ());
+
   /* Identify the pattern that contains element I and work out the index of
      the last encoded element for that pattern.  */
   unsigned int pattern = i % m_npatterns;