x86: Properly find the maximum stack slot alignment

Don't assume that stack slots can only be accessed by stack or frame
registers.  We first find all registers defined by stack or frame
registers.  Then check memory accesses by such registers, including
stack and frame registers.

gcc/

	PR target/109780
	PR target/109093
	* config/i386/i386.cc (stack_access_data): New.
	(ix86_update_stack_alignment): Likewise.
	(ix86_find_all_reg_use_1): Likewise.
	(ix86_find_all_reg_use): Likewise.
	(ix86_find_max_used_stack_alignment): Also check memory accesses
	from registers defined by stack or frame registers.

gcc/testsuite/

	PR target/109780
	PR target/109093
	* g++.target/i386/pr109780-1.C: New test.
	* gcc.target/i386/pr109093-1.c: Likewise.
	* gcc.target/i386/pr109780-1.c: Likewise.
	* gcc.target/i386/pr109780-2.c: Likewise.
	* gcc.target/i386/pr109780-3.c: Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Co-Authored-By: Uros Bizjak <ubizjak@gmail.com>

6 files changed, 360 insertions, 21 deletions

diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 3171d6e..dd07624 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -8473,6 +8473,123 @@ output_probe_stack_range (rtx reg, rtx end)
   return "";
 }
 
+/* Data passed to ix86_update_stack_alignment.  */
+struct stack_access_data
+{
+  /* The stack access register.  */
+  const_rtx reg;
+  /* Pointer to stack alignment.  */
+  unsigned int *stack_alignment;
+};
+
+/* Update the maximum stack slot alignment from memory alignment in PAT.  */
+
+static void
+ix86_update_stack_alignment (rtx, const_rtx pat, void *data)
+{
+  /* This insn may reference stack slot.  Update the maximum stack slot
+     alignment if the memory is referenced by the stack access register. */
+  stack_access_data *p = (stack_access_data *) data;
+
+  subrtx_iterator::array_type array;
+  FOR_EACH_SUBRTX (iter, array, pat, ALL)
+    {
+      auto op = *iter;
+      if (MEM_P (op) && reg_mentioned_p (p->reg, op))
+	{
+	  unsigned int alignment = MEM_ALIGN (op);
+
+	  if (alignment > *p->stack_alignment)
+	    *p->stack_alignment = alignment;
+	  break;
+	}
+    }
+}
+
+/* Helper function for ix86_find_all_reg_uses.  */
+
+static void
+ix86_find_all_reg_uses_1 (HARD_REG_SET &regset,
+			  rtx set, unsigned int regno,
+			  auto_bitmap &worklist)
+{
+  rtx dest = SET_DEST (set);
+
+  if (!REG_P (dest))
+    return;
+
+  /* Reject non-Pmode modes.  */
+  if (GET_MODE (dest) != Pmode)
+    return;
+
+  unsigned int dst_regno = REGNO (dest);
+
+  if (TEST_HARD_REG_BIT (regset, dst_regno))
+    return;
+
+  const_rtx src = SET_SRC (set);
+
+  subrtx_iterator::array_type array;
+  FOR_EACH_SUBRTX (iter, array, src, ALL)
+    {
+      auto op = *iter;
+
+      if (MEM_P (op))
+	iter.skip_subrtxes ();
+
+      if (REG_P (op) && REGNO (op) == regno)
+	{
+	  /* Add this register to register set.  */
+	  add_to_hard_reg_set (&regset, Pmode, dst_regno);
+	  bitmap_set_bit (worklist, dst_regno);
+	  break;
+	}
+    }
+}
+
+/* Find all registers defined with register REGNO.  */
+
+static void
+ix86_find_all_reg_uses (HARD_REG_SET &regset,
+			unsigned int regno, auto_bitmap &worklist)
+{
+  for (df_ref ref = DF_REG_USE_CHAIN (regno);
+       ref != NULL;
+       ref = DF_REF_NEXT_REG (ref))
+    {
+      if (DF_REF_IS_ARTIFICIAL (ref))
+	continue;
+
+      rtx_insn *insn = DF_REF_INSN (ref);
+
+      if (!NONJUMP_INSN_P (insn))
+	continue;
+
+      unsigned int ref_regno = DF_REF_REGNO (ref);
+
+      rtx set = single_set (insn);
+      if (set)
+	{
+	  ix86_find_all_reg_uses_1 (regset, set,
+				    ref_regno, worklist);
+	  continue;
+	}
+
+      rtx pat = PATTERN (insn);
+      if (GET_CODE (pat) != PARALLEL)
+	continue;
+
+      for (int i = 0; i < XVECLEN (pat, 0); i++)
+	{
+	  rtx exp = XVECEXP (pat, 0, i);
+
+	  if (GET_CODE (exp) == SET)
+	    ix86_find_all_reg_uses_1 (regset, exp,
+				      ref_regno, worklist);
+	}
+    }
+}
+
 /* Set stack_frame_required to false if stack frame isn't required.
    Update STACK_ALIGNMENT to the largest alignment, in bits, of stack
    slot used if stack frame is required and CHECK_STACK_SLOT is true.  */
@@ -8491,10 +8608,6 @@ ix86_find_max_used_stack_alignment (unsigned int &stack_alignment,
   add_to_hard_reg_set (&set_up_by_prologue, Pmode,
 		       HARD_FRAME_POINTER_REGNUM);
 
-  /* The preferred stack alignment is the minimum stack alignment.  */
-  if (stack_alignment > crtl->preferred_stack_boundary)
-    stack_alignment = crtl->preferred_stack_boundary;
-
   bool require_stack_frame = false;
 
   FOR_EACH_BB_FN (bb, cfun)
@@ -8506,27 +8619,67 @@ ix86_find_max_used_stack_alignment (unsigned int &stack_alignment,
 				       set_up_by_prologue))
 	  {
 	    require_stack_frame = true;
-
-	    if (check_stack_slot)
-	      {
-		/* Find the maximum stack alignment.  */
-		subrtx_iterator::array_type array;
-		FOR_EACH_SUBRTX (iter, array, PATTERN (insn), ALL)
-		  if (MEM_P (*iter)
-		      && (reg_mentioned_p (stack_pointer_rtx,
-					   *iter)
-			  || reg_mentioned_p (frame_pointer_rtx,
-					      *iter)))
-		    {
-		      unsigned int alignment = MEM_ALIGN (*iter);
-		      if (alignment > stack_alignment)
-			stack_alignment = alignment;
-		    }
-	      }
+	    break;
 	  }
     }
 
   cfun->machine->stack_frame_required = require_stack_frame;
+
+  /* Stop if we don't need to check stack slot.  */
+  if (!check_stack_slot)
+    return;
+
+  /* The preferred stack alignment is the minimum stack alignment.  */
+  if (stack_alignment > crtl->preferred_stack_boundary)
+    stack_alignment = crtl->preferred_stack_boundary;
+
+  HARD_REG_SET stack_slot_access;
+  CLEAR_HARD_REG_SET (stack_slot_access);
+
+  /* Stack slot can be accessed by stack pointer, frame pointer or
+     registers defined by stack pointer or frame pointer.  */
+  auto_bitmap worklist;
+
+  add_to_hard_reg_set (&stack_slot_access, Pmode, STACK_POINTER_REGNUM);
+  bitmap_set_bit (worklist, STACK_POINTER_REGNUM);
+
+  if (frame_pointer_needed)
+    {
+      add_to_hard_reg_set (&stack_slot_access, Pmode,
+			   HARD_FRAME_POINTER_REGNUM);
+      bitmap_set_bit (worklist, HARD_FRAME_POINTER_REGNUM);
+    }
+
+  unsigned int regno;
+
+  do
+    {
+      regno = bitmap_clear_first_set_bit (worklist);
+      ix86_find_all_reg_uses (stack_slot_access, regno, worklist);
+    }
+  while (!bitmap_empty_p (worklist));
+
+  hard_reg_set_iterator hrsi;
+  stack_access_data data;
+
+  data.stack_alignment = &stack_alignment;
+
+  EXECUTE_IF_SET_IN_HARD_REG_SET (stack_slot_access, 0, regno, hrsi)
+    for (df_ref ref = DF_REG_USE_CHAIN (regno);
+	 ref != NULL;
+	 ref = DF_REF_NEXT_REG (ref))
+      {
+	if (DF_REF_IS_ARTIFICIAL (ref))
+	  continue;
+
+	rtx_insn *insn = DF_REF_INSN (ref);
+
+	if (!NONJUMP_INSN_P (insn))
+	  continue;
+
+	data.reg = DF_REF_REG (ref);
+	note_stores (insn, ix86_update_stack_alignment, &data);
+      }
 }
 
 /* Finalize stack_realign_needed and frame_pointer_needed flags, which
diff --git a/gcc/testsuite/g++.target/i386/pr109780-1.C b/gcc/testsuite/g++.target/i386/pr109780-1.C
new file mode 100644
index 0000000..7e3eabd
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr109780-1.C
@@ -0,0 +1,72 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target c++17 } */
+/* { dg-options "-O2 -mavx2 -mtune=haswell" } */
+
+template <typename _Tp> struct remove_reference {
+  using type = __remove_reference(_Tp);
+};
+template <typename T> struct MaybeStorageBase {
+  T val;
+  struct Union {
+    ~Union();
+  } mStorage;
+};
+template <typename T> struct MaybeStorage : MaybeStorageBase<T> {
+  char mIsSome;
+};
+template <typename T, typename U = typename remove_reference<T>::type>
+constexpr MaybeStorage<U> Some(T &&);
+template <typename T, typename U> constexpr MaybeStorage<U> Some(T &&aValue) {
+  return {aValue};
+}
+template <class> struct Span {
+  int operator[](long idx) {
+    int *__trans_tmp_4;
+    if (__builtin_expect(idx, 0))
+      *(int *)__null = false;
+    __trans_tmp_4 = storage_.data();
+    return __trans_tmp_4[idx];
+  }
+  struct {
+    int *data() { return data_; }
+    int *data_;
+  } storage_;
+};
+struct Variant {
+  template <typename RefT> Variant(RefT) {}
+};
+long from_i, from___trans_tmp_9;
+namespace js::intl {
+struct DecimalNumber {
+  Variant string_;
+  unsigned long significandStart_;
+  unsigned long significandEnd_;
+  bool zero_ = false;
+  bool negative_;
+  template <typename CharT> DecimalNumber(CharT string) : string_(string) {}
+  template <typename CharT>
+  static MaybeStorage<DecimalNumber> from(Span<const CharT>);
+  void from();
+};
+} // namespace js::intl
+void js::intl::DecimalNumber::from() {
+  Span<const char16_t> __trans_tmp_3;
+  from(__trans_tmp_3);
+}
+template <typename CharT>
+MaybeStorage<js::intl::DecimalNumber>
+js::intl::DecimalNumber::from(Span<const CharT> chars) {
+  DecimalNumber number(chars);
+  if (auto ch = chars[from_i]) {
+    from_i++;
+    number.negative_ = ch == '-';
+  }
+  while (from___trans_tmp_9 && chars[from_i])
+    ;
+  if (chars[from_i])
+    while (chars[from_i - 1])
+      number.zero_ = true;
+  return Some(number);
+}
+
+/* { dg-final { scan-assembler-not "and\[lq\]?\[^\\n\]*-32,\[^\\n\]*sp" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr109093-1.c b/gcc/testsuite/gcc.target/i386/pr109093-1.c
new file mode 100644
index 0000000..58a7b00
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr109093-1.c
@@ -0,0 +1,33 @@
+/* { dg-do run  { target avx2_runtime } }  */
+/* { dg-options "-O2 -mavx2 -mtune=znver1 -ftrivial-auto-var-init=zero -fno-stack-protector" } */
+
+int a, b, c, d;
+char e, f = 1;
+short g, h, i;
+
+__attribute__ ((weak))
+void
+run (void)
+{
+  short j;
+
+  for (; g >= 0; --g)
+    {
+      int *k[10];
+
+      for (d = 0; d < 10; d++)
+	k[d] = &b;
+
+      c = *k[1];
+
+      for (; a;)
+	j = i - c / f || (e ^= h);
+    }
+}
+
+int
+main (void)
+{
+  run ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr109780-1.c b/gcc/testsuite/gcc.target/i386/pr109780-1.c
new file mode 100644
index 0000000..6b06947
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr109780-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -march=skylake" } */
+
+char perm[64];
+
+void
+__attribute__((noipa))
+foo (int n)
+{
+  for (int i = 0; i < n; ++i)
+    perm[i] = i;
+}
+
+/* { dg-final { scan-assembler-not "and\[lq\]?\[^\\n\]*-32,\[^\\n\]*sp" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr109780-2.c b/gcc/testsuite/gcc.target/i386/pr109780-2.c
new file mode 100644
index 0000000..152da06
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr109780-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -march=skylake" } */
+
+#define N 9
+
+void
+f (double x, double y, double *res)
+{
+  y = -y;
+  for (int i = 0; i < N; ++i)
+    {
+      double tmp = y;
+      y = x;
+      x = tmp;
+      res[i] = i;
+    }
+  res[N] = y * y;
+  res[N + 1] = x;
+}
+
+/* { dg-final { scan-assembler-not "and\[lq\]?\[^\\n\]*-32,\[^\\n\]*sp" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr109780-3.c b/gcc/testsuite/gcc.target/i386/pr109780-3.c
new file mode 100644
index 0000000..a3a770a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr109780-3.c
@@ -0,0 +1,46 @@
+/* { dg-do run  { target avx2_runtime } }  */
+/* { dg-options "-O2 -mavx2 -mtune=znver1 -fno-stack-protector -fno-stack-clash-protection" } */
+
+char a;
+static int b, c, f;
+char *d = &a;
+static char *e = &a;
+
+__attribute__ ((weak))
+void
+g (int h, int i)
+{
+  int j = 1;
+  for (; c != -3; c = c - 1)
+    {
+      int k[10];
+      f = 0;
+      for (; f < 10; f++)
+        k[f] = 0;
+      *d = k[1];
+      if (i < *d)
+        {
+          *e = h;
+          for (; j < 9; j++)
+            {
+              b = 1;
+              for (; b < 7; b++)
+                ;
+            }
+        }
+    }
+}
+
+__attribute__ ((weak))
+void
+run (void)
+{
+  g (1, 1);
+}
+
+int
+main (void)
+{
+  run ();
+  return 0;
+}