rs6000: Fix wrong align passed to build_aligned_type [PR88309]

As the comments in PR88309 show, there are two oversights
in rs6000_gimple_fold_builtin that pass align in bytes to
build_aligned_type but which actually requires align in
bits, it causes unexpected ICE or hanging in function
is_miss_rate_acceptable due to zero align_unit value.

This patch is to fix them by converting bytes to bits, add
an assertion on positive align_unit value and notes function
build_aligned_type requires align measured in bits in its
function comment.

	PR target/88309

Co-authored-by: Andrew Pinski <quic_apinski@quicinc.com>

gcc/ChangeLog:

	* config/rs6000/rs6000-builtin.cc (rs6000_gimple_fold_builtin): Fix
	wrong align passed to function build_aligned_type.
	* tree-ssa-loop-prefetch.cc (is_miss_rate_acceptable): Add an
	assertion to ensure align_unit should be positive.
	* tree.cc (build_qualified_type): Update function comments.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr88309.c: New test.

4 files changed, 33 insertions, 3 deletions

diff --git a/gcc/config/rs6000/rs6000-builtin.cc b/gcc/config/rs6000/rs6000-builtin.cc
index 6698274..e7d6204 100644
--- a/gcc/config/rs6000/rs6000-builtin.cc
+++ b/gcc/config/rs6000/rs6000-builtin.cc
@@ -1900,7 +1900,7 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
 	tree lhs_type = TREE_TYPE (lhs);
 	/* In GIMPLE the type of the MEM_REF specifies the alignment.  The
 	  required alignment (power) is 4 bytes regardless of data type.  */
-	tree align_ltype = build_aligned_type (lhs_type, 4);
+	tree align_ltype = build_aligned_type (lhs_type, 32);
 	/* POINTER_PLUS_EXPR wants the offset to be of type 'sizetype'.  Create
 	   the tree using the value from arg0.  The resulting type will match
 	   the type of arg1.  */
@@ -1944,7 +1944,7 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
 	tree arg2_type = ptr_type_node;
 	/* In GIMPLE the type of the MEM_REF specifies the alignment.  The
 	   required alignment (power) is 4 bytes regardless of data type.  */
-	tree align_stype = build_aligned_type (arg0_type, 4);
+	tree align_stype = build_aligned_type (arg0_type, 32);
 	/* POINTER_PLUS_EXPR wants the offset to be of type 'sizetype'.  Create
 	   the tree using the value from arg1.  */
 	gimple_seq stmts = NULL;
diff --git a/gcc/testsuite/gcc.target/powerpc/pr88309.c b/gcc/testsuite/gcc.target/powerpc/pr88309.c
new file mode 100644
index 0000000..c0078cf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr88309.c
@@ -0,0 +1,27 @@
+/* { dg-require-effective-target powerpc_vsx_ok } */
+/* { dg-options "-mvsx -O2 -fprefetch-loop-arrays" } */
+
+/* Verify there is no ICE or hanging.  */
+
+#include <altivec.h>
+
+void b(float *c, vector float a, vector float, vector float)
+{
+  vector float d;
+  vector char ahbc;
+  vec_xst(vec_perm(a, d, ahbc), 0, c);
+}
+
+vector float e(vector unsigned);
+
+void f() {
+  float *dst;
+  int g = 0;
+  for (;; g += 16) {
+    vector unsigned m, i;
+    vector unsigned n, j;
+    vector unsigned k, l;
+    b(dst + g * 3, e(m), e(n), e(k));
+    b(dst + (g + 4) * 3, e(i), e(j), e(l));
+  }
+}
diff --git a/gcc/tree-ssa-loop-prefetch.cc b/gcc/tree-ssa-loop-prefetch.cc
index bbd98e0..70073cc 100644
--- a/gcc/tree-ssa-loop-prefetch.cc
+++ b/gcc/tree-ssa-loop-prefetch.cc
@@ -739,6 +739,8 @@ is_miss_rate_acceptable (unsigned HOST_WIDE_INT cache_line_size,
   if (delta >= (HOST_WIDE_INT) cache_line_size)
     return false;
 
+  gcc_assert (align_unit > 0);
+
   miss_positions = 0;
   total_positions = (cache_line_size / align_unit) * distinct_iters;
   max_allowed_miss_positions = (ACCEPTABLE_MISS_RATE * total_positions) / 1000;
diff --git a/gcc/tree.cc b/gcc/tree.cc
index f801712..787168e 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -5689,7 +5689,8 @@ build_qualified_type (tree type, int type_quals MEM_STAT_DECL)
   return t;
 }
 
-/* Create a variant of type T with alignment ALIGN.  */
+/* Create a variant of type T with alignment ALIGN which
+   is measured in bits.  */
 
 tree
 build_aligned_type (tree type, unsigned int align)